STRUCTURE FOR FLOOR AND FOUNDATION FOR EXPANSIVE GROUND COUNTERMEASURES AND METHOD FOR CONSTRUCTING STRUCTURE FOR FLOOR AND FOUNDATION FOR EXPANSIVE GROUND 5 COUNTERMEASURES
[Technical Field]
[0001]
The present invention relates to a structure of a foundation and a floor for expansive ground countermeasures appropriate for constructing a structure such as a 10 building or the like on expansive ground, and a construction method of a structure of a foundation and a floor for expansive ground countermeasures.
Priority is claimed on Japanese Patent Application No. 2013-044273, filed March 6, 2013, Japanese Patent Application No. 2013-085068, filed April 15, 2013, and Japanese Patent Application No. 2013-090170, filed April 23, 2013, the contents 15 of which are incorporated herein by reference.
[Background Art]
[0002]
For example, in arid and quasi-arid areas such as Southeast Asia, Africa, the Middle East, and the like, expansive soil including clay minerals having expansibility 20 such as montmorillonite or the like accumulates, and such expansive soil (ground that exhibits expansibility), which expands according to submersion/water absorption during rainy periods and contracts according to drainage/drying during dry periods, occupies a large area.
[0003] 25
Therefore, as shown in Fig. 22, when a structure 2 such as a house, a factory, or the like is constructed on such expansive soil 1, according to ground deformation due to expansion and contraction of the expansive soil 1 between a rainy period and a dry period, damage such as uneven rising or uneven sinking, cracks in a wall or a floor of the structure 2, irregularity (deviation) due to local swelling of tiles of a first floor, 30 or the like occurs to a great extent in the structure 2.
[0004]
In particular, in a production facility (factory), there is a need to maintain 2
horizontal precision of a floor (a floor structure of a first floor) at a certain high level of precision in order for a manufacturing apparatus to perform an operation or a forklift to travel smoothly, and even when an expansion pressure is received, it is strongly required to prevent irregularity in the floor.
[0005] 5
For this reason, in the related art, the following four methods are used alone or in combination to construct a structure while employing expansive soil countermeasures.
[0006]
In the first method, after all of the ground 1 exhibiting expansibility under the 10 structure is substituted with high quality soil 3, the structure 2 is formed as a direct foundation support type, or a first floor is constructed as a dirt floor. Alternatively, after the ground 1 exhibiting expansibility is solidified by cement or lime, the structure 2 is formed as a direct foundation support type, or a first floor is constructed as a dirt floor (see Fig. 23). 15
[0007]
In the second method, stakes 5 are installed in a support layer of high quality ground 4 that does not exhibit expansibility, and the stakes 5 resist a floating force when the ground 1 expands, thus preventing harmful deformation of the structure 2 (see Fig. 24, for example, Patent Document 1). 20
[0008]
In the third method, soil of an earth surface section 1a that floats when the ground 1 expands is inserted into (accommodated in) an aperture portion, a jig 6 configured to absorb shock such that an expansive force is not directly applied to the structure is laid on the earth surface section 1a, and the structure is constructed on the 25 jig 6 in a direct foundation support type or constructs the floor (see Fig. 25).
[0009]
In the fourth method, stakes 5 are installed in a support layer of high quality ground 4 that does not show expansibility, a floating floor (a structure floor) 7 is constructed to be connected to the stakes 5 and disposed over a ground surface (an 30 earth surface section) 1a, and expansion of the ground 1 is absorbed by a cavity between the floor 7 and the ground 1 (see Fig. 26).
[Citation List] 3
[Patent Document]
[0010]
[Patent Document 1] Japanese Unexamined Patent Application, First Publication No. 2008-174936
[Summary of Invention] 5
[Technical Problems]
[0011]
However, in the above-mentioned first expansive soil countermeasures, in order to substitute the entire stratum with the high quality soil or agitate and mix cement or lime throughout the entire stratum to be solidified, a construction period is 10 prolonged when a thickness of the stratum exhibiting expansibility is greater, which increases costs. For example, when a large-scale factory or the like is constructed in a planar fashion, if there is a need to process a stratum exhibiting expansibility of 3 m or more, the construction period becomes extremely long and enormous cost is needed.
[0012] 15
In the above-mentioned second expansive soil countermeasures, as the entire structure is supported by the stakes, floating or sinking of the structure due to expansion/contraction of the expansive soil can be effectively prevented, but because of the large-scale countermeasures, the construction period and cost are much greater than in the direct foundation type with no stakes. For this reason, application to 20 structures such as small and medium buildings is practically impossible.
[0013]
A flat slab between stakes needs to be constructed/designed to resist expansion pressure. For this reason, for example, a stake installation interval is reduced to 2 to 4 m and a number of arranged reinforcing bars of the flat slab needs to 25 be increased to be greater than that of the conventional structure floor, and therefore the construction period is lengthened and enormous cost is needed.
[0014]
In the above-mentioned third expansive soil countermeasures, an exclusive jig is expensive, and in fields and zones in which structures are constructed, particularly in 30 developing countries, the exclusive jig is frequently hard to acquire and apply. In addition, since considerable effort and labor are necessary to install the exclusive jig over the entire surface, the exclusive jig is hard to apply to large-scale factories,
4
production facilities, or the like, in a planar fashion.
[0015]
Because a floating floor is prepared in the above-mentioned fourth expansive soil countermeasures, a large-scale mold is needed when the floor concrete is placed. On the other hand, although using a plywood mold (wood) is inexpensive, for example, 5 in arid/quasi-arid areas, ants may cause damage. Then, since ants may intrude indoors through gaps formed by the ants in joint sections in the concrete construction or pipelines, there are cases in which use of plywood molds is impossible.
Meanwhile, when a half PCa slab (a precast mold) is used, a large crane is needed to hoist a heavy PC mold. In this case, for example, there are many areas in 10 which expansive ground occupies a wide range in developing countries, and thus large cranes are hard to supply to such areas. In addition, while use of a deck plate for a structure floor may be considered, in many cases, since the deck plate is more expensive than the concrete material, it is difficult to purchase the deck plate in developing countries. 15
[Solution to Problem]
[0016]
According to a first aspect of the present invention, a structure of a foundation and a floor for expansive ground countermeasures of a structure is a floor structure for expansive ground countermeasures of a structure constructed on the ground that 20 exhibits expansibility, the structure including: a first buffer layer formed by filling a granular material in a ditch extending in one direction or a ditch formed in a grid shape when seen in plan view, which is formed by excavating the ground, or a first buffer layer formed by laying the granular material on the ground while filling the granular material in the ditch; and a floor slab formed on the first buffer layer and the ground. 25
[0017]
In the structure of the foundation and the floor for expansive ground countermeasures according to the first aspect of the present invention, a particle diameter D50 of the granular material when a transmission mass percentage obtained by particle size distribution is 50 % may be 20 mm or more. 30
[0018]
In the structure of the foundation and the floor for expansive ground countermeasures according to the first aspect of the present invention, provided that an
5
excavation width in the other direction perpendicular to the one direction when seen in plan view is a, an excavation width of the one direction when the ditch is formed in the grid shape is d, an excavation depth of the ditch is c, an interval of the ditch in the other direction is M, and an interval of the ditch in the one direction when the ditch is formed in the grid shape is N, the ditch may be formed to satisfy a ≥ 0.5m, d ≥ 0.5m, c 5 ≥ 0.5m, M ≤ 5c + a, and N ≤ 5c + d.
[0019]
According to a second aspect of the present invention, a structure of a foundation and a floor for expansive ground countermeasures of a structure is a structure of a foundation and a floor for expansive ground countermeasures of a 10 structure constructed on the ground that exhibits expansibility, the structure including: a tubular member formed in a substantially U-shaped cross section, placed on a ground surface of the ground, and having an opening section directed downward; an expansion suppressing soil layer laid on the ground surface of the ground while burying at least a portion of the tubular member; a second buffer layer overlaid by laying a granular 15 material on the expansion suppressing soil layer; a level concrete layer overlaid by pouring concrete on the second buffer layer; and a floor slab formed on the level concrete layer, wherein the expansion suppressing soil layer is formed to include a plurality of penetration sections in which an expansion suppressing soil penetrates into the ground by excavating the ground to form a plurality of depressions, pulverizing the 20 excavated soil obtained by excavating the ground to generate the expansion suppressing soil, and laying the expansion suppressing soil on the ground surface of the ground while finishing the expansion suppressing soil to absorb an expansion pressure from the ground to fill the depressions.
[0020] 25
In the structure of the foundation and the floor for expansive ground countermeasures according to the second aspect of the present invention, the plurality of penetration sections may be aligned at predetermined intervals, and the tubular members may be laid on the ground surface between the neighboring penetration sections to be arranged in a grid shape. 30
[0021]
In the structure of the foundation and the floor for expansive ground countermeasures according to the second aspect of the present invention, the expansion 6
suppressing soil may be generated by pulverizing the excavated soil obtained by excavating the ground and mixing slaked lime with the pulverized soil.
[0022]
According to a third aspect of the present invention, a construction method of a structure of a foundation and a floor for expansive ground countermeasures is a 5 method of constructing a structure of a floor for expansive ground countermeasures of a structure on the ground that exhibits expansibility, the method including: a ground pit excavation process of excavating the ground to form a plurality of depressions; a tubular member installation process of placing a tubular member formed in a substantially U-shaped cross section on the ground surface of the ground such that an 10 opening section is directed downward; an expansion suppressing soil layer-forming process of pulverizing the excavated soil obtained through the ground pit excavation process to generate an expansion suppressing soil, and laying the expansion suppressing soil on the ground surface of the ground to form an expansion suppressing soil layer while finishing the expansion suppressing soil to absorb an expansion 15 pressure from the ground to fill the depressions; a buffer layer-forming process of laying a granular material on the expansion suppressing soil layer to overlay and form a second buffer layer; a level concrete layer-forming process of pouring concrete on the second buffer layer to overlay and form a level concrete layer; and a floor slab forming process of forming a floor slab on the level concrete layer. 20
[0023]
In the construction method of the structure of the foundation and floor for expansive ground countermeasures according to the third aspect of the present invention, the method may include an expansion suppressing soil generating process of mixing slaked lime while pulverizing the excavated soil obtained through the ground 25 pit excavation process to generate an expansion suppressing soil.
[0024]
According to a fourth aspect of the present invention, a structure of a foundation and a floor for expansive ground countermeasures is a foundation structure for expansive ground countermeasures configured to construct a structure on the 30 ground that exhibits expansibility, the structure is constituted by an outer circumferential region of an outer circumferential section side of the structure serving as a stake foundation, and an internal region inside the outer circumferential region 7
serving as a direct foundation.
[0025]
In the structure of the foundation and the floor for expansive ground countermeasures according to the fourth aspect of the present invention, a distance X from an outer circumferential edge to the internal region of the structure may be set to 5 a large value of a distance X = a coefficient of permeability k of the ground × a period t1 in which water comes in continuous or intermittent contact with the ground and expansion is continuously or intermittently generated in the ground, and a distance X = a coefficient of permeability k of the ground × a period t2 in which water does not come in continuous contact with the ground of a certain level or more. 10
[0026]
According to a fifth aspect of the present invention, a structure of a foundation and a floor for expansive ground countermeasures is a foundation structure for expansive ground countermeasures for constructing a structure on the ground that exhibits expansibility, the structure including: a water-shielding structure section 15 continuously formed to surround the structure when seen in plan view and extending to a predetermined depth from the ground surface; and a ground reform-processed section formed by reforming and processing the ground of a predetermined depth range from the ground surface at a portion surrounded by the water-shielding structure section, wherein a ground depth at which expansion due to contact with water penetrating into 20 the ground and contraction due to drying are repeated is specified, and the water-shielding structure section is formed to penetrate into at least the specified ground depth at which the expansion and the contraction are repeated.
[0027]
In the structure of the foundation and the floor for expansive ground 25 countermeasures, at least one investigation and/or test of literature/document investigation, in situ ground investigation, and a soil test of a soil sample collected from the ground may be performed to specify the specified ground depth at which the expansion and the contraction are repeated, and the water-shielding structure section is formed. 30
[0028]
In the structure of the foundation and the floor for expansive ground countermeasures according to the fifth aspect of the present invention, moisture weight 8
percentages of the ground in a rainy season and a dry season may be measured at a plurality of places from the ground surface in the depth direction, and the water-shielding structure section may be formed to penetrate to at least the specified ground depth at which a difference between the moisture weight percentages in the rainy season and the dry season is smaller than a preset value such that no bad influence to 5 the structure due to expansion in the rainy season is applied.
[0029]
In the structure of the foundation and the floor for expansive ground countermeasures according to the fifth aspect of the present invention, the ground reform-processed section may include a third buffer layer formed by excavating an 10 internal ground surrounded by the water-shielding structure section from the ground surface and spreading a filler having a particle diameter of an order of several cm to tens cm, a protective layer formed of a sheet-shaped member laid on the third buffer layer and configured to protect the third buffer layer, and a solidification-processed soil layer formed by rolling and compacting a mixed soil mixed with cement or lime 15 on the protective layer.
[0030]
In the structure of the foundation and the floor for expansive ground countermeasures according to the fifth aspect of the present invention, the sheet-shaped member may be a geosynthetic or water-proof sheet. 20
[0031]
In the structure of the foundation and the floor for expansive ground countermeasures according to the fifth aspect of the present invention, the water-shielding structure section may be formed to penetrate to at least the specified ground depth at which a difference between the moisture weight percentages in the rainy 25 season and the dry season is 5 % or less.
[0032]
In the structure of the foundation and the floor for expansive ground countermeasures according to the fifth aspect of the present invention, the ground reform-processed section may include a level concrete layer formed by pouring 30 concrete on the solidification-processed soil layer.
[0033]
In the structure of the foundation and the floor for expansive ground 9
countermeasures according to the fifth aspect of the present invention, the ground reform-processed section may include a ventilation pipe reaching the third buffer layer from the ground surface.
[0034]
According to a sixth aspect of the present invention, a construction method of 5 a structure of a foundation and a floor for expansive ground countermeasures is a method of constructing a structure of a foundation and a floor for expansive ground countermeasures for constructing a structure on the ground that exhibits expansibility, the method including: a specified ground depth investigation process of specifying a ground depth at which expansion due to contact with water intruded into the ground 10 and contraction due to drying are repeated; a water-shielding structure section-forming process of forming a water-shielding structure section continuously formed to surround the structure when seen in plan view and penetrated from the ground surface to at least the ground depth specified through the specified ground depth investigation process; a buffer layer-forming process of forming a third buffer layer by excavating an internal 15 ground surrounded by the water-shielding structure section from the ground surface and spreading a filler having a particle diameter of an order of several cm to tens cm; a protective layer-forming process of forming a protective layer by laying a sheet-shaped member on the third buffer layer to protect the third buffer layer; and a solidification-processed soil layer-forming process of forming a solidification-processed soil layer on 20 the protective layer by mixing cement or lime and rolling and compacting the mixed soil.
[0035]
In the construction method of the structure of the foundation and the floor for expansive ground countermeasures according to the sixth aspect of the present 25 invention, in the specified ground depth investigation process, at least one investigation and/or test of literature/document investigation, in situ ground investigation, and a soil test of a soil sample collected from the ground may be performed to specify a specified ground depth at which the expansion and the contraction are repeated. 30
[0036]
In the construction method of the structure of the foundation and the floor for expansive ground countermeasures according to the sixth aspect of the present 10
invention, the specified ground depth investigation process may include a ground investigation process of measuring moisture weight percentages in a rainy season and a dry season of the ground that exhibits expansibility at a plurality of places from the ground surface in a depth direction, and a water-shielding structure section depth determination process of obtaining a difference between the moisture weight 5 percentage in the rainy season and the moisture weight percentage in the dry season of the ground and specifying a ground depth at which no bad influence to the surface due to expansion in the rainy season is applied.
[Advantageous Effects of Invention]
[0037] 10
In the structure of the foundation and the floor for expansive ground countermeasures according to the first aspect of the present invention, the expansive soil of the in situ soil is excavated to form the ditch extending in one direction or the ditch in a grid shape when seen in plan view, a granular material such as crushed stones or the like is filled in the ditch to form the first buffer layer, and a floor slab is 15 formed on the first buffer layer. Accordingly, when the ground that exhibits expansibility expands, an expansion pressure can be absorbed by the first buffer layer, and as the granular material is filled in the ditch to form the first buffer layer, an expansion pressure in the vertical direction can be effectively absorbed. Accordingly, swelling in the first floor (the floor slab) on the first buffer layer due to expansion of 20 the expansive ground can be prevented. Thus, according to the above-mentioned configuration and construction, effective expansive soil countermeasures can be adopted at a low cost.
[0038]
In addition, in the structure of the foundation and the floor for expansive 25 ground countermeasures according to the first aspect of the present invention, by using a substance having a particle diameter D50 of 20 mm or more when the transmission mass percentage obtained through particle size distribution is 50% as the granular material, even when displacement in the horizontal direction of the expansive ground is allowed by the first buffer layer, the expansion pressure in the horizontal direction 30 and the vertical direction can be appropriately reduced without earth and sand falling into the ditch.
[0039] 11
Further, in the structure of the foundation and the floor for expansive ground countermeasures according to the first aspect of the present invention, provided that an excavation width in the other direction perpendicular to the one direction when seen in plan view is a, an excavation width of the one direction when the ditch is formed in the grid shape is d, an excavation depth of the ditch is c, an interval of the ditch in the 5 other direction is M, and an interval of the ditch in the one direction when the ditch is formed in the grid shape is N, when not only the ditch and but also the first buffer layer may be formed to satisfy a ≥ 0.5 m, d ≥ 0.5 m, c ≥ 0.5 m, M ≤ 5c+a, and N ≤ 5c+d, a ratio of width/height (M−a)/c and (N−d)/c of a residual section (a protrusion) of the ground protruding while forming the ditch is 5 or less. Accordingly, when 10
ground that exhibits expansibility expands, the expansion pressure, in particular, the expansion pressure in the vertical direction, can be more reliably and effectively absorbed by the first buffer layer.
[0040]
In the structure of the foundation and the floor for expansive ground 15 countermeasures according to the second embodiment of the present invention, and the construction method of the structure of the foundation and the floor for expansive ground countermeasures according to the third aspect of the present invention, the expansion suppressing soil layer is formed by excavating the expansive soil of the in situ soil and burying and leveling the expansive soil, for example, without rolling 20 compaction, the second buffer layer is formed by laying the granular material such as crushed stones or the like, and the level concrete layer is formed by pouring level concrete. Accordingly, when the ground that exhibits expansibility expands, the expansion pressure can be absorbed by the expansion suppressing soil layer or the second buffer layer, and further, the expansion pressure can be caught by the level 25 concrete layer. Accordingly, swelling in the first floor (the floor slab) formed on the level concrete layer according to expansion of the expansive ground can be prevented. Thus, according to the above-mentioned configuration and construction, effective expansive soil countermeasures can be adopted at a low cost.
[0041] 30
In addition, since the expansion suppressing soil layer and the level concrete layer that are buried and finished without rolling compaction also function as a mold when the concrete of the first floor slab is placed, a plywood mold, a precast mold, a
12
deck plate, or the like is not needed when the floating floor is constructed, and thus workability and reliability of the floor structure can be improved.
[0042]
In the structure of the foundation and the floor for expansive ground countermeasures according to the fourth aspect of the present invention, a planar range 5 in which the ground sinks or expands under the influence of rainfall or moisture evaporation is specified, and because a foundation structure configured to support a structure is constructed using an outer circumferential region of the structure under which the ground is assumed to expand or sink as a stake foundation and using an internal region inside the outer circumferential region serving as a direct foundation, 10 expansive soil countermeasures of the structure can be reasonably adopted at a lower cost than in the countermeasures of the related art for supporting the entire structure on the stake foundation.
[0043]
In the structure of the foundation and the floor for expansive ground 15 countermeasures according to the fifth aspect of the present invention, and the construction method of the structure of the foundation and the floor for expansive ground countermeasures according to the sixth aspect of the present invention, intrusion of moisture into the internal ground immediately under the structure can be suppressed (or prevented) by the water-shielding structure section. Accordingly, 20 repetition of the expansion and contraction of the expansive soil of the internal ground surrounded by the water-shielding structure section can be suppressed (prevented), and damage such as cracks or the like due to application of an external force to the surface according to the expansion and contraction of the ground that exhibits expansibility can be prevented. 25
[0044]
In addition, here, the ground depth at which expansion due to contact with water that has intruded into the ground and contraction due to drying are repeated is specified, and the water-shielding structure section is formed to penetrate to at least the specified ground depth at which the expansion and the contraction are repeated. Thus, 30 more specifically, for example, ground investigation is performed during a rainy period and a dry period, a difference between the moisture weight percentage during a rainy period and the moisture weight percentage during the dry period of the ground that
13
exhibits expansibility is obtained, and the water-shielding structure section is formed to penetrate to a depth less than a predetermined value at which the difference between the moisture weight percentages does not harm the structure due to expansion in a rainy period. As a result, repetition of the expansion and contraction of the expansive soil of the internal ground surrounded by the water-shielding structure section can be 5 reliably suppressed (prevented).
[0045]
That is, (only) the ground in which the expansion and contraction are repeated is surrounded by the water-shielding structure section, rather than all of the ground of the expansive soil, for example, (only) the ground that expands and contracts during a 10 rainy period and the dry period is surrounded, and the moisture weight percentage of the internal ground can be maintained in a stable state throughout the year. Accordingly, damage such as cracks or the like in the structure due to expansion of the ground immediately under the structure and the expansion pressure thereof can be reliably prevented. 15
[0046]
In addition, as the ground reform-processed section (the third buffer layer, the protective layer, and the solidification-processed soil layer) obtained by reforming and processing the ground at the portion surrounded by the water-shielding structure section and a predetermined depth range from the ground surface is provided, even 20 when water intrudes into the internal ground surrounded by the water-shielding structure section and expansion occurs, the ground expansion pressure can be attenuated using the ground reform-processed section. Accordingly, even when water intrudes into the internal ground surrounded by the water-shielding structure section, application of the expansion pressure to the structure can be suppressed, and damage 25 such as cracks or the like in the structure can be more reliably prevented.
[0047]
Accordingly, according to the structure of the foundation and the floor for expansive ground countermeasures according to the fifth aspect of the present invention and the construction method of the structure of the foundation and the floor 30 for expansive ground countermeasures according to the sixth aspect of the present invention, expansive soil countermeasures of the structure can be adopted at a lower cost than the related art, and when the water-shielding structure section configured to 14
suppress a variation in moisture weight percentage of the ground and the ground reform-processed section configured to attenuate the ground expansion pressure are combined, expansive soil countermeasures having high reliability can be realized.
[Brief Description of Drawings]
[0048] 5
Fig. 1 is a view showing a structure of a foundation and a floor for expansive ground countermeasures (a foundation structure for expansive ground countermeasures) according to a first embodiment of the present invention;
Fig. 2 is a view showing the structure of the foundation and the floor for expansive ground countermeasures (the foundation structure for expansive ground 10 countermeasures) according to the first embodiment of the present invention;
Fig. 3 is a view showing the structure of the foundation and the floor for expansive ground countermeasures (the foundation structure for expansive ground countermeasures) according to the first embodiment of the present invention;
Fig. 4A is a view showing a deformed state of the structure upon ground 15 expansion;
Fig. 4B is a view showing a deformed state of the structure upon ground contraction;
Fig. 5 is a cross-sectional view showing a structure of a foundation and a floor for expansive ground countermeasures (a foundation structure for expansive ground 20 countermeasures) according to a second embodiment of the present invention;
Fig. 6 is a view taken along line X1-X1 of Fig. 5, serving as plan view showing an outer circumferential region and an internal region of the structure of the foundation and the floor for expansive ground countermeasures (the foundation structure for expansive ground countermeasures) according to the embodiment of the 25 present invention;
Fig. 7 is a view showing an example of an estimation equation for estimating a coefficient of permeability based on a particle diameter accumulation curve;
Fig. 8 is a view showing a structure of a foundation and a floor for expansive ground countermeasures (a floor structure for expansive ground countermeasures) 30 according to a third embodiment of the present invention;
Fig. 9A is a view showing a state in which the ground is excavated to form depressions in a construction method of a structure of a foundation and a floor for
15
expansive ground countermeasures (a floor structure for expansive ground countermeasures) according to the third embodiment of the present invention;
Fig. 9B is a view showing the state in which the ground is excavated to form the depressions in the construction method of the structure of the foundation and the floor for expansive ground countermeasures (the floor structure for expansive ground 5 countermeasures) according to the third embodiment of the present invention;
Fig. 10A is a view showing a state in which tubular members are laid in the construction method of the structure of the foundation and the floor for expansive ground countermeasures (the floor structure for expansive ground countermeasures) according to the third embodiment of the present invention; 10
Fig. 10B is a view showing the state in which the tubular members are laid in the construction method of the structure of the foundation and the floor for expansive ground countermeasures (the floor structure for expansive ground countermeasures) according to the third embodiment of the present invention;
Fig. 11A is a view showing a state in which an expansion suppressing soil 15 layer is formed in the construction method of the structure of the foundation and the floor for expansive ground countermeasures (the floor structure for expansive ground countermeasures) according to the third embodiment of the present invention;
Fig. 11B is a view showing the state in which the expansion suppressing soil layer is formed in the construction method of the structure of the foundation and the 20 floor for expansive ground countermeasures (the floor structure for expansive ground countermeasures) according to the third embodiment of the present invention;
Fig. 12A is a view showing a state in which a second buffer layer and a level concrete layer are formed in the construction method of the structure of the foundation and the floor for expansive ground countermeasures (the floor structure for expansive 25 ground countermeasures) according to the third embodiment of the present invention;
Fig. 12B is a view showing the state in which the second buffer layer and the level concrete layer are formed in the construction method of the structure of the foundation and the floor for expansive ground countermeasures (the floor structure for expansive ground countermeasures) according to the third embodiment of the present 30 invention;
Fig. 13A is a view showing a structure of a foundation and a floor for expansive ground countermeasures (a floor structure for expansive ground 16
countermeasures) according to a fourth embodiment of the present invention;
Fig. 13B is a view showing the structure of the foundation and the floor for expansive ground countermeasures (the floor structure for expansive ground countermeasures) according to the fourth embodiment of the present invention;
Fig. 14A is a view showing a state in which a ditch and a first buffer layer of 5 the structure of the foundation and the floor for expansive ground countermeasures (the floor structure for expansive ground countermeasures) according to the fourth embodiment of the present invention are formed;
Fig. 14B is a view showing the state in which the ditch and the first buffer layer of the structure of the foundation and the floor for expansive ground 10 countermeasures (the floor structure for expansive ground countermeasures) according to the fourth embodiment of the present invention are formed;
Fig. 15 is plan view showing a state in which a ditch extending in one direction is formed in the structure of the foundation and the floor for expansive ground countermeasures (the floor structure for expansive ground countermeasures) 15 according to the fourth embodiment of the present invention;
Fig. 16 is a taken along line X1-X1 of Fig. 15;
Fig. 17 is plan view showing a state in which a ditch having a grid shape is formed in the structure of the foundation and the floor for expansive ground countermeasures (the floor structure for expansive ground countermeasures) according 20 to the fourth embodiment of the present invention;
Fig. 18 is a view taken along line X1-X1 of Fig. 17;
Fig. 19 is a view taken along line X2-X2 of Fig. 17;
Fig. 20 is a view showing test results of soil compared by measuring expansion pressures of expansive soil in a vertical direction under different conditions; 25
Fig. 21 is a view used for description of effects of the structure of the foundation and the floor for expansive ground countermeasures (the floor structure for expansive ground countermeasures) according to the fourth embodiment of the present invention;
Fig. 22 is a view showing a state in which an expansion pressure is applied to 30 a structure constructed on the ground that exhibits expansibility;
Fig. 23 is a view showing expansive soil countermeasures of the related art and showing a state in which the ground that exhibits expansibility under the structure 17
is entirely substituted with high quality soil;
Fig. 24 is a view showing expansive soil countermeasures of the related art and showing a state in which stakes are installed in a support layer of high quality ground that does not exhibit expansibility;
Fig. 25 is a view showing expansive soil countermeasures of the related art 5 and showing a state in which a jig configured to absorb a shock such that an expansive force is not directly applied to the structure is laid on the earth surface section.
Fig. 26 is a view showing expansive soil countermeasures of the related art and showing a state in which stakes are installed in a support layer of high quality ground that does not exhibit expansibility, and a floating floor is supported by the 10 stakes.
[Detailed Description of Embodiments]
[0049]
Hereinafter, a structure of a foundation and a floor for expansive ground countermeasures according to a first embodiment of the present invention, and a 15 construction method of the structure of the foundation and the floor for expansive ground countermeasures will be described with reference to Figs. 1 to 3. Here, the embodiment relates to a structure of a foundation for expansive ground countermeasures by which a structure such as a building can be constructed on expansive soil (ground that exhibits expansibility) including clay minerals having 20 expansibility such as montmorillonite or the like that occupy a wide range in arid and quasi-arid areas such as Southeast Asia, Africa, the Middle East, and the like, and a construction method thereof.
[0050]
As shown in Figs. 1 and 2, a structure (a foundation structure for expansive 25 ground countermeasures) A of a foundation and a floor for expansive ground countermeasures of the embodiment is constituted by a water-shielding structure section 10 continuously formed to surround a structure when seen in plan view and extending from a ground surface (an earth surface section 1a) to a predetermined depth, and a ground reform-processed section 11 disposed at a portion surrounded by the 30 water-shielding structure section 10 and configured to reform and process the ground in the predetermined depth range from the ground surface 1a.
[0051] 18
The water-shielding structure section 10 is, for example, a soil cement peristyle wall, and is disposed at an outer circumferential section of a structure such as a building or the like, or at a position spaced a predetermined distance from the outer circumferential section of the structure. In addition, as the water-shielding structure section 10 is continuously formed to surround the structure when seen in the plan view, 5 the water-shielding structure section 10 divides the ground into surrounded internal ground 1b and external ground 1c so that rain water (water such as rain water or the like) is prevented from intruding into the internal ground 1b or cannot easily intrude into the internal ground 1b.
[0052] 10
Further, the water-shielding structure section 10 is not limited to the soil cement peristyle wall as long as intrusion of water such as rain water or the like into the internal ground 1b can be prevented (suppressed), and for example, another material or structure that exhibits a water-shielding property, such as installation of a sheet pile, burying of a water-shielding sheet, construction of a cement bentonite wall, 15 and so on, may be applied.
[0053]
In addition, as shown in Fig. 1, a ground depth h generated by repeating expansion caused by contact with water that has intruded into the ground 1 and contraction caused by drying is specified, and the water-shielding structure section 10 20 is formed to penetrate to the specified ground depth h generated by repeating the expansion and the contraction. More specifically, for example, moisture weight percentages of the ground 1 during a rainy period and a dry period are measured at a plurality of places in a depth direction from the ground surface (the earth surface section 1a), and the water-shielding structure section 10 penetrates to at least a depth at 25 which a difference between the moisture weight percentages in a rainy period and the dry period is smaller than a preset value such that the structure is not harmed by the ground expanding in a rainy period. In the embodiment, as shown in Fig. 1, the water-shielding structure section 10 is formed to penetrate to a depth at which the difference between the moisture weight percentage Ww in a rainy period and the 30 moisture weight percentage Wd in the dry period is 5% or less (Ww−Wd ≤ 5%).
[0054]
Meanwhile, the ground reform-processed section 11 is configured to include a 19
third buffer layer 12 formed by excavating the internal ground 1b surrounded by the water-shielding structure section 10 from the ground surface (the earth surface section 1a) and spreading a filler having a particle diameter of an order of several cm to tens of cm, for example, broken stones having diameters of 10 cm to 20 cm, a protective layer 13 formed by laying a geotextile (geosynthetic) or a waterproof sheet on the third 5 buffer layer 12, a solidification-processed soil layer 14 formed by adding and mixing cement or lime to and with in situ soil and rolling and compacting the mixed soil on the protective layer 13, and a level concrete layer 15 formed by pouring concrete on the solidification-processed soil layer 14.
[0055] 10
In addition, in the embodiment, the internal ground 1b surrounded by the water-shielding structure section 10 is excavated from the ground surface 1a to a depth of 60 cm or more, the third buffer layer 12 is formed to have a layer thickness of 30 cm or more from an excavated bottom, and the solidification-processed soil layer 14 is formed to have a layer thickness of 30 cm or more. In addition, the solidification-15 processed soil layer 14 is formed by rolling and compacting the mixed soil obtained by adding and mixing the cement or lime to and with the in situ soil at an addition amount of, for example, 20 to 150 kg/m3. Here, while both quicklime and slaked lime may be used as the lime, the quicklime may be used when a stronger solidification layer is formed. 20
[0056]
Further, in the ground reform-processed section 11 of the embodiment, as shown in Fig. 3, a ventilation pipe 16 that reaches from the ground surface to the third buffer layer 12 is provided, and exchange of air (circulation and distribution of air) is performed via the ventilation pipe 16 between gaps of the third buffer layer 12 formed 25 by spreading the filler such as broken stones or the like and the ground surface (the inside of the structure 2 or the like).
[0057]
Next, in construction of the structure of the foundation and the floor for expansive ground countermeasures of the embodiment (the foundation structure for 30 expansive ground countermeasures) A constituted by the above-mentioned configuration (in a construction method of the structure of the foundation and the floor for expansive ground countermeasures of the embodiment (the foundation structure for
20
expansive ground countermeasures) A), first, when the structure 2 such as a building or the like is constructed, the ground depth h at which repetition of expansion due to contact with water that has intruded into the ground 1 and contraction due to drying is generated is specified (a specified ground depth investigation process). More specifically, in the embodiment, moisture weight percentages of the ground 1 that 5 exhibits expansibility in a rainy period and the dry period are measured at a plurality of places in a depth direction from the ground surface 1a (a ground investigation process/a specified ground depth investigation process). In addition, here, for example, the expansive soil 1 that exhibits expansibility may be collected in the dry period, and investigation of soil quality such as a swelling property (expansibility), 10 dynamic properties, or the like, may be performed.
[0058]
Then, as shown in Fig. 1, a difference between the moisture weight percentage in a rainy period and the moisture weight percentage in the dry period of the ground 1 is obtained, and a ground depth at which the structure 2 is not harmed by expansion in 15 a rainy period is specified (a water-shielding structure section depth determination process/a specified ground depth investigation process). In the embodiment, a depth at which the difference between the moisture weight percentages is 5% or less is the ground depth at which the structure 2 is not harmed by expansion in a rainy period.
[0059] 20
Then, the water-shielding structure section 10 is formed to penetrate to at least the ground depth specified in the specified ground depth investigation process (a water-shielding structure section-forming process). That is, in the embodiment, after the depth at which the difference between the moisture weight percentages in a rainy period and the dry period is 5% or less is determined as described above, the water-25 shielding structure section 10 is formed at the outer circumferential section of the structure range continuously to surround the structure 2 when seen in the plan view and to at least penetrate to the determined depth.
[0060]
Next, the internal ground 1b surrounded by the water-shielding structure 30 section 10 is excavated, and the filler having a particle diameter of an order of several cm to tens of cm such as broken stones or the like is spread to a predetermined layer thickness from the excavated bottom to form the third buffer layer 12 (a buffer layer-
21
forming process). In addition, the sheet-shaped member such as a geotextile or a waterproof sheet is laid on the third buffer layer 12 to form the protective layer 13 (a protective layer-forming process).
[0061]
In a step of forming the protective layer 13 as described above, for example, 5 the in situ soil such as soil obtained by excavating the internal ground 1b surrounded by the water-shielding structure section 10 is prepared, the cement or lime is added and mixed to and with the in situ soil at a predetermined amount, and the mixed soil is rolled and compacted on the protective layer 13 to form the solidification-processed soil layer 14 having a predetermined thickness (a solidification-processed soil layer-10 forming process).
[0062]
In addition, the concrete is poured on the solidification-processed soil layer 14 such that the upper surface is disposed at a predetermined height level to form the level concrete layer 15 (a level concrete layer-forming process). After that, the structure is 15 constructed on the level concrete layer 15 in a direct foundation type (a structure construction process).
[0063]
Further, in a step before forming the level concrete layer 15, the ventilation pipe 16 for ventilation to the third buffer layer 12 is installed (a ventilation pipe 20 installation process). Then, after the structure 2 is constructed, for example, air-conditioned indoor air is forcedly supplied and circulated through the gaps of the third buffer layer 12 constituted by the broken stones or the like via the ventilation pipe 16.
[0064]
Thus, in the structure of the foundation and floor for expansive ground 25 countermeasures of the embodiment, and the construction method of the structure of the foundation and the floor for expansive ground countermeasures (the foundation structure A for expansive ground countermeasures and the construction method of the foundation structure A for expansive ground countermeasures), intrusion of moisture into the internal ground 1b immediately under the structure 2 can be suppressed (or 30 prevented) by the water-shielding structure section 10. Accordingly, repeated expansion and contraction of the expansive soil of the internal ground 1b surrounded by the water-shielding structure section 10 can be suppressed, damage to the structure 22
2 such as cracks or the like due to application of the external force according to the expansion and the contraction of the ground 1 that exhibits expansibility can be prevented.
[0065]
In addition, here, the ground depth at which repetition of expansion due to 5 contact with water that has intruded into the ground 1 and contraction due to drying is generated is specified, and the water-shielding structure section 10 is formed to penetrate at least to the specified ground depth at which the repeated expansion and contraction are generated. More specifically, for example, ground investigation is performed during a rainy period and the dry period, and a difference between the 10 moisture weight percentage in a rainy period and the moisture weight percentage in the dry period of the ground 1 that exhibits expansibility is obtained. The water-shielding structure section 10 is formed to penetrate to a depth smaller than a preset value such that the difference between the moisture weight percentages due to expansion in a rainy period does not harm the structure 2. As a result, repeated 15 expansion and contraction of the expansive soil of the internal ground 1b surrounded by the water-shielding structure section 10 can be reliably suppressed.
[0066]
That is, (only) the ground in which the expansion and the contraction repeat, rather than all of the ground of the expansive soil, is surrounded by the water-shielding 20 structure section 10, for example, (only) the ground that expands and contracts in a rainy period and the dry period is surrounded, and the moisture weight percentage of the internal ground 1b can be maintained in a stable state throughout the year. In addition, when the water-shielding structure section 10 is formed to penetrate to a depth at which the difference between the moisture weight percentage in a rainy period 25 and the moisture weight percentage in the dry period of the ground 1 that exhibits expansibility is 5% or less, the moisture weight percentage of the internal ground 1b can be maintained in a stable state throughout the year. Accordingly, expansion of the ground 1 immediately under the structure 2 and damage such as cracks or the like from occurring in the structure 2 due to the expansion pressure are prevented. 30
[0067]
Here, strictly speaking, the water-shielding structure section 10 may be formed to penetrate to the ground depth at which no expansion and contraction occurs. 23
However, in performing the ground investigation, dispersion, measurement errors, or the like, of the ground are included in the moisture weight percentage obtained by performing the soil test.
On the other hand, when the difference between the moisture weight percentages in a rainy period and the dry period is 5% or less as described above, it can 5 be determined that the difference is within an error range. That is, the inventor(s) of the application learned that, in clay ground that exhibits expansibility, when the ground depth is 10 m or more at which the influence of rainfall/drying of the earth surface is considered to be small, in many cases, the moisture weight percentage of the clay is 40 to 60%. Further, if dispersion (a coefficient of variation) of the moisture weight 10 percentage is assumed based on past cases to be 0.05 to 0.1, standard deviation of the moisture weight percentage becomes (40 to 60%)×(0.05 to 0.1) = 2 to 6%. When a standard for the accuracy of the moisture weight percentage obtained in the soil test is a probability exceeding 10% (a value widely used in technical fields dealing with ground), an error is 1.28×standard deviation = 1.28×(2 to 6%) = 2.56 to 7.68%, and a 15 median is about 5%. Accordingly, when there are two measurement values of the moisture weight percentages and a difference therebetween is 5% or less, it is within an assumed range of the dispersion, and the two moisture weight percentages may be considered to be equal to each other. Accordingly, like the embodiment, when the water-shielding structure section 10 is formed to penetrate to the depth at which the 20 difference between the moisture weight percentage Ww in a rainy period and the moisture weight percentage Wd in the dry period is 5% or less, it can be reliably determined that expansion/contraction of the ground (displacement/pressure from the expansion/contraction) is not generated at a level that will damage the structure.
[0068] 25
In addition, as the ground reform-processed section 11 (the third buffer layer 12, the protective layer 13, and the solidification-processed soil layer 14) disposed at the portion surrounded by the water-shielding structure section 10 and formed by reforming and processing the ground of a predetermined depth range from the ground surface 1a is provided, even when water intrudes into the internal ground 1b 30 surrounded by the water-shielding structure section 10 and expansion occurs, the ground expansion pressure can be absorbed by the ground reform-processed section 11. Accordingly, even when the water intrudes into the internal ground 1b surrounded by 24
the water-shielding structure section 10, application of the expansion pressure to the structure 2 can be suppressed, and damage to the structure 2 such as cracks or the like can be more reliably prevented.
[0069]
That is, since the ground reform-processed section 11 includes the third buffer 5 layer 12 formed by spreading the filler such as broken stones or the like, when the water intrudes into the internal ground 1b surrounded by the water-shielding structure section 10 and the expansive soil of the internal ground 1b expands, as the expansive soil enters (penetrates) the gaps of the filler such as broken stones or the like upon the expansion, the expansive force (the expansion pressure) of the ground 1 can be 10 absorbed and attenuated. Accordingly, even when the water intrudes into the internal ground 1b surrounded by the water-shielding structure section 10, no uneven rising or sinking occurs in the structure 2, and damage to the structure 2 such as cracks or the like can be more reliably prevented.
[0070] 15
Further, the geosynthetic of the protective layer 13 that protects the third buffer layer 12 and the solidification-processed soil layer 14 obtained by mixing cement or lime with the in situ soil and rolling and compacting them are installed between the third buffer layer 12 and the structure 2. For this reason, when the water intrudes into the internal ground 1b surrounded by the water-shielding structure section 20 10 and the expansive soil of the internal ground 1b expands, ground stiffness can be increased by the geosynthetic 9 or the solidification-processed soil layer 14 and the expansive force of the internal ground 1b can be blocked while absorbing and attenuating the expansive force of the internal ground 1b in the third buffer layer 12. Accordingly, even when the water intrudes into the internal ground 1b surrounded by 25 the water-shielding structure section 10, damage to the structure 2 such as cracks or the like and uneven rising or sinking of the structure 2 can be more reliably prevented. In addition, since the concrete is poured onto the solidification-processed soil layer 14 to form the level concrete layer 15, when the water intrudes into the internal ground 1b surrounded by the water-shielding structure section 10, the expansive force of the 30 internal ground 1b can also be blocked by the level concrete layer 15.
[0071]
Further, when the waterproof sheet is formed as the protective layer 13,
25
intrusion of the water into the internal ground 1b can be prevented by the waterproof sheet 9 together with the level concrete layer 15. In other words, the internal ground 1b can be protected from water by the waterproof sheet 9 such that no great difference in moisture weight percentage of the internal ground 1b surrounded by the water-shielding structure section 10 in a rainy period and the dry period is generated. 5 Accordingly, repeated expansion and contraction of the expansive soil of the ground 1 under the structure 2 can be more reliably suppressed, and damage to the structure 2 such as cracks or the like can be prevented.
[0072]
Further, as the indoor air conditioned through the ventilation pipe 16 is 10 circulated through the filler gaps of the third buffer layer 12 and the air is distributed between the gaps of the third buffer layer 12 and the ground, the moisture weight percentage of the expansive soil immediately under the structure surrounded by the water-shielding structure section 10 can be constantly maintained. Accordingly, repeated expansion and contraction of the expansive soil of the ground 1 under the 15 structure 2 can be more reliably suppressed, and damage to the structure 2 such as cracks or the like can be prevented.
[0073]
Thus, according to the structure of the foundation and the floor for expansive ground countermeasures of the embodiment (the foundation structure for expansive 20 ground countermeasures) A, expansive soil countermeasures of the structure 2 can be adopted using a general ground material available in the field at low cost in comparison with the related art. In addition, as the water-shielding structure section 10 configured to suppress a variation in the moisture weight percentage of the ground 1 and the ground reform-processed section 11 configured to attenuate the ground 25 expansion pressure are combined, expansive soil countermeasures having high reliability can be realized.
[0074]
Meanwhile, in general, a vermiculite group, a smectite group, and a halloysite group are known as minerals that exhibit expansibility. In particular, in the smectite 30 group, that is, among beidellite, nontronite, saponite, hectorite, sauconite, stevensite, and montmorillonite of the smectite group, montmorillonite is rich in expansibility (a swelling property), and bentonite (or acid clay) having montmorillonite as a main
26
element is known as a representative expansive clay.
[0075]
In addition, for example, the montmorillonite forms a crystalline structure in which a unit crystal layer is charged with a negative electric charge, and cations such as Na+, K+, Ca2+, Mg2+, H+ or the like are inserted between the unit crystal layers. 5 Then, a difference in a swelling property is generated due to the cation inserted between the unit crystal layers. For example, a volume of a Na type into which Na+ is inserted is increased (swelled) tenfold or more when it comes in contact with water, whereas a volume of a Ca type into which Ca2+ is inserted only increases about 1/10 as much as the Na type even when it comes in contact with water because Ca2+ attracts 10 the unit crystal layer more strongly than Na+.
[0076]
Here, in the structure of the foundation and the floor for expansive ground countermeasures of the embodiment (the foundation structure for expansive ground countermeasures) A, the solidification-processed soil layer 14 formed by mixing 15 cement or lime ((quicklime or slaked lime) with the in situ soil and rolling and compacting them is formed between the third buffer layer 12 and the structure 2. For this reason, when the water intrudes into the internal ground 1b surrounded by the water-shielding structure section 10, Ca2+ (calcium) is eluted from the cement or the lime mixed with the in situ soil while the water is in contact with the solidification-20 processed soil layer 14. For this reason, Ca2+ can come in contact with the ground 1 that exhibits a swelling property such as montmorillonite or the like together with water. Then, for example, as Ca2+ comes in contact with Na type montmorillonite, the Na type can be varied to a Ca type by substituting Na+ wit Ca2+ between the unit crystal layers. That is, the ground 1 that exhibits expansibility can be automatically 25 changed into ground having extremely little expansibility.
[0077]
Further, when the water comes in contact with the cement or the lime of the solidification-processed soil layer 14, a pH of the water can be increased to become alkaline. Specifically, when the water comes in contact with the cement, the pH of 30 the water can be maximally increased to pH 12.6 when it comes in contact with the cement and to pH 12.4 when it comes in contact with the slaked lime.
In addition, for example, the montmorillonite disappears or changes into 27
calcium aluminate hydrate (CAH) or calcium silicate hydrate (CSH) when it comes in contact with a calcium solution (alkaline water) with a pH of 11 or more.
[0078]
For this reason, in the structure of the foundation and the floor for expansive ground countermeasures of the embodiment (the foundation structure for expansive 5 ground countermeasures) A, when the water intrudes into the internal ground 1b surrounded by the water-shielding structure section 10, pH is increased as the water (rain water) comes in contact with the cement or the lime of the solidification-processed soil layer 14, and the alkaline water having the increased pH can come in contact with the ground that exhibits the swelling property such as montmorillonite or 10 the like. Then, for example, as the alkaline water with the pH of 11 or more (the rain water having the increased pH) comes in contact with the montmorillonite, the ground 1 that exhibits expansibility can be automatically changed into ground having extremely little expansibility.
[0079] 15
Accordingly, according to the structure of the foundation and the floor for expansive ground countermeasures of the embodiment (the foundation structure for expansive ground countermeasures) A (and the construction method of the structure of the foundation and the floor for expansive ground countermeasures of the embodiment (the foundation structure for expansive ground countermeasures) A), as the 20 solidification-processed soil layer 14 including the cement or the lime is formed between the third buffer layer 12 and the structure 2, even when the water intrudes into the internal ground 1b surrounded by the water-shielding structure section 10, characteristics of the ground 1 that exhibits expansibility can be varied, and generation of the expansion pressure can also be suppressed. 25
[0080]
The first embodiment of the structure of the foundation and the floor for expansive ground countermeasures of the embodiment, and the construction method of the structure of the foundation and the floor for expansive ground countermeasures of the embodiment according to the present invention have been described above, but the 30 present invention is not limited to the first embodiment and appropriate modifications may be made without departing from the spirit of the present invention.
[0081] 28
For example, the ground depth at which expansion due to contact with water that has intruded into the ground 1 and contraction due to drying are repeated may be specified, and the water-shielding structure section according to the present invention may be formed to penetrate to at least the specified ground depth at which the expansion and the contraction are repeated. For this reason, like the embodiment, it 5 is unnecessary to limit measurement of the moisture weight percentages of the ground 1 in a rainy period and the dry period at a plurality of places in the depth direction from the ground surface 1a, and the water-shielding structure section is formed to penetrate to the depth at which the difference between the moisture weight percentages in a rainy period and the dry period is smaller than a preset value at which expansion 10 of the ground in a rainy period not to harm the structure 2.
[0082]
That is, when the specified ground depth at which the expansion and the contraction are repeated is specified (in the specified ground depth investigation process), in addition to the method of measuring the moisture weight percentages in a 15 rainy period and the dry period, at least one investigation and/or test of literature/document investigation, in situ ground investigation, and a soil test of a soil sample collected from the ground may be performed, and the specified ground depth at which the expansion and the contraction are repeated may be specified through the investigation and the test, to form the water-shielding structure section. 20
[0083]
More specifically, in the literature/document investigation, geographical history and literature or documents on results of ground investigation and soil tests performed in the past are investigated. For example, in “Hamberg, D. J (1985). A simplified method for predicting heave in expansive soils. M. S. thesis, Colorado State 25 University, Fort Collins, CO,” a result of investigation of a (periodical) variation of moisture weight percentage of the ground in warm and cold periods is disclosed. Here, the variation in the moisture weight percentage is reduced at a depth of 5 to 8 m. Accordingly, the ground depth can be specified by investigating conventional literature or documents. 30
[0084]
In addition, in situ ground investigation, for example, geophysical exploration such as electrical logging, elastic wave speed logging, or the like, of the ground,
29
sounding such as various penetration tests or the like, an in situ density test using stab sand and water substitution, a sand substitution method, or the like, displacement measurement using underground distortion or the like, and so on, is selectively performed. Based on the results, the specified ground depth at which the expansion and the contraction are repeated can be specified. 5
[0085]
Further, with respect to the soil samples collected from the ground, in addition to the moisture weight percentage measurement, various soil tests such as a permeability test, a consolidation test, a uniaxial compression test, a triaxial compression test, a single shear test, and so on, are selectively performed, and based 10 on the results, the specified ground depth at which the expansion and the contraction are repeated can be specified.
[0086]
In addition, of course, the water-shielding structure section 10 may be formed to a depth that reaches the ground (stratum) 4 that does not exhibit expansibility. 15
[0087]
Further, in the embodiment, while the ground reform-processed section 11 is configured to include the level concrete layer 15 and further include the ventilation pipe 16, the level concrete layer 15 and the ventilation pipe 16 may not be included.
[0088] 20
Next, a structure of a foundation and a floor for expansive ground countermeasures according to a second embodiment of the present invention will be described with reference to Figs. 4A to 7. Further, like the first embodiment, the embodiment relates to a structure of a foundation for expansive ground countermeasures configured for constructing a structure such as a building or the like 25 on expansive soil (ground that exhibits expansibility) including clay minerals having expansibility such as montmorillonite or the like that occupy a wide range in arid and quasi-arid areas, for example, Southeast Asia, Africa, the Middle East, and the like. Accordingly, the same components as in the first embodiment are described with the same reference numerals. 30
[0089]
Here, as shown in Figs. 4A and 4B, when a surface area of the structure 2 is large, for example, when the structure 2 is a factory or the like, in the ground 1 under 30
the structure 2, intrusion of the rain water into the ground 1 or evaporation of the soil moisture from the ground surface 1a and expansion and sinking of the ground 1 are likely to occur near the outer circumferential edge (an outer circumferential section, or an outer wall surface 2a) of the structure 2. Meanwhile, a central portion of the structure 2 is covered by, for example, a roof, or the ground surface 1a is covered by a 5 concrete floor slab. For this reason, intrusion of the rain water into the ground 1 or evaporation of the soil moisture from the ground surface 1a cannot easily occur, and no expansion or sinking of the ground 1 occurs.
[0090]
Based on such a phenomenon, in a structure of a foundation and a floor for 10 expansive ground countermeasures of the embodiment (a foundation structure for expansive ground countermeasures) B, as shown in Fig. 5 (a cross-sectional view) and Fig. 6 (plan view), the single structure 2 is divided into a region of an outer circumferential section side of the structure 2 (an outer circumferential region S1) and a region of an inner side of the structure 2 (an internal region S2) when seen in plan 15 view, and different foundation structures are applied to the regions S1 and S2.
[0091]
Specifically, the structure of the foundation and the floor for expansive ground countermeasures of the embodiment (the foundation structure for expansive ground countermeasures) B is constituted by a stake foundation 17 serving as a foundation 20 structure of the outer circumferential region S1 and a direct foundation 18 serving as a foundation structure of the internal region S2. In addition, the outer circumferential region S1 is within a range of a distance X calculated by either the following Equation (1) or Equation (2) from an outer circumferential edge (an outer wall surface) 2a of the structure 2, and the internal region S2 is within a range further inside than a position of 25 the distance X from the outer circumferential edge 2a of the structure 2. In addition, in the embodiment, the larger value between Equation (1) and Equation (2) is employed as the distance X.
[0092]
Distance X = {(coefficient of permeability k)×(duration t1 of one continuous 30 rainy period)}…Equation (1)
Distance X = {(coefficient of permeability k)×(duration t2 of one continuous dry period)}…Equation (2) 31
[0093]
Here, a coefficient of permeability k is determined by performing the permeability test in situ. Alternatively, the coefficient of permeability k is determined by collecting the soil quality sample having little disturbance and performing the consolidation test or the permeability test. Alternatively, the coefficient of 5 permeability is determined through estimation based on a particle diameter accumulation curve obtained by collecting the soil quality sample and performing the particle size test. Further, as a method of estimating the coefficient of permeability based on the particle diameter accumulation curve, for example, a Creager’s estimation equation based on a particle diameter of 20% as shown in Fig. 7 is provided. 10
[0094]
In addition, the above-mentioned Equation (1) and Equation (2), for example, a case in which a rainy period and the dry period can be somewhat clearly distinguished throughout one year is assumed. For this reason, “the duration t1 of the one continuous rainy period” in Equation (1) is “a period t1 in which water comes in 15 continuous or intermittent contact with the ground 1 and expansion continuously or intermittently occurs in the ground 1.” In addition, “the duration t2 of the one continuous dry period” in Equation (2) is “a period t2 in which water is continuously not in contact with the ground to a certain extent or more.”
[0095] 20
Then, in the embodiment, the outer circumferential region S1 of the structure 2 set as described above is a region facing the outer circumferential section 2a of the structure section 2, and becomes a range that is influenced by intrusion of the rain water into the ground 1 in a rainy period and evaporation of the soil moisture from the ground surface 1a in the dry period. That is, the range is a range having a large 25 variation in moisture weight percentage.
[0096]
Accordingly, in the outer circumferential region S1, the ground 1 under the structure 2 expands in a rainy period and sinks in the dry period. For this reason, in the embodiment, the foundation structure of the outer circumferential region S1 is used 30 as the stake foundation 17 (a foundation stake (a stake support) 5 that reaches the support layer of the high quality ground 4 that does not exhibit expansibility), the first floor is used as a structure slab (a floating floor), and the stake 5 resists a floating force 32
upon expansion of the ground 1 to prevent harmful deformation of the structure 2.
[0097]
Next, in the embodiment, the internal region S2 is disposed further inside the structure 2 than the outer circumferential region S1, for example, a roof is hung therefrom, and the ground surface 1a is covered by the concrete floor. For this reason, 5 the region is a range in which intrusion of the rain water into the ground 1 in a rainy period and evaporation of the soil moisture from the ground surface 1a in the dry period do not occur (do not easily occur) (a range in which no variation in moisture weight percentage occurs).
[0098] 10
Accordingly, in the internal region S2, there is no expansion or sinking of the ground under the structure. For this reason, in the embodiment, the foundation structure of the internal region S2 is used as the direct foundation 18 and the first floor is used as the dirt floor form, and even when the foundation structure of the internal region S2 is configured in this way, no harmful deformation occurs in the structure 2. 15
[0099]
Here, a boundary position between the outer circumferential region S1 and the internal region S2 of the structure 2, i.e., a trial calculation example of the distance X calculated according to the above-mentioned Equation (1) and Equation (2) from the outer circumferential edge (the outer wall surface) 2a of the structure ,2 is shown. 20
[0100]
In the trial calculation example of the distance X, as the condition (1), in one year, a rainy period was about five months, and the dry period was about seven months. In addition, as the condition (2), the soil quality sample having little disturbance was collected and the consolidation test was performed, and as a result, the coefficient of 25 permeability k of the expansive ground 1 was an order of 10−4 cm/sec.
[0101]
Thus, according to Equation (1), distance X = {(0.0001 cm/sec)×5 months×30 days×24 hours×60 minutes×60 seconds} = 1296 cm, and according to Equation (2), distance X = {(0.0001 cm/sec)×7 months×30 days×24 hours×60 minutes×60 seconds} 30 = 1814 cm.
[0102]
Accordingly, the larger value between the values obtained by Equation (1) and
33
Equation (2) is employed, and the distance X is set to 1814 cm. Then, since the distance X is about 18 m, a range of a horizontal distance of 18 m or less inside of the outer circumferential edge 2a of the structure 2 is the outer circumferential region S1, and the stake foundation 17 and the structure slab (the floating floor) of the first floor are constructed within that range. In addition, an inner range of a horizontal distance 5 of more than 18 m from the outer circumferential edge 2a of the structure 2 is the internal region S2, and the direct foundation 18 and the first floor of the dirt floor form are constructed within that range.
[0103]
Accordingly, in the structure of the foundation and the floor for expansive 10 ground countermeasures of the embodiment configured as described above (the foundation structure for expansive ground countermeasures) B, a planar range in which expansion or sinking of the ground 1 occurs due to the influence of the rainfall and the moisture evaporation is specified. As the foundation structure configured to support the structure 2 is constructed using the outer circumferential region S1 of the structure 15 2 in which it is assumed that the expansion and the sinking of the ground 1 occur as the stake foundation 17 and the internal region S2 inside the outer circumferential region S1 as the direct foundation 18, expansive soil countermeasures of the structure can be reasonably adopted at a lower cost than the countermeasures of the related art in which the entire structure is supported by the stake foundation. 20
[0104]
In addition, as the distance X (the range of the outer circumferential region S1) from the outer circumferential edge 2a to the internal region S2 of the structure 2 is set to the larger value between a distance X = a coefficient of permeability k of the ground×a period t1 in which water comes in continuous or 25 intermittent contact with the ground and expansion is continuously or intermittently generated in the ground, and a distance X = a coefficient of permeability k of the ground×a period t2 in which water is continuously not in contact with the ground to a certain extent or more, a planar range of the external region S2 in which expansion or sinking of the ground 1 occurs due to the influence of the rainfall and moisture 30 evaporation can be reliably and precisely specified. Accordingly, harmful deformation of the structure 2 due to the expansion and the contraction of the ground 1 can be more reliably and effectively prevented. 34
[0105]
While the second embodiment of the structure of the foundation and floor for expansive ground countermeasures according to the present invention has been described above, the present invention is not limited to the second embodiment but may be appropriately modified without departing from the spirit of the present 5 invention.
[0106]
Next, a structure of a foundation and a floor for expansive ground countermeasures according to a third embodiment of the present invention, and a construction method of the structure of the foundation and the floor for expansive 10 ground countermeasures will be described with reference to Figs. 8 to 12B. Here, the embodiment relates to a structure of a floor for expansive ground countermeasures configured for constructing a structure such as a building or the like on expansive soil (the ground that exhibits expansibility) including clay minerals having expansibility such as montmorillonite or the like that occupy a wide range in arid and quasi-arid 15 areas, for example, Southeast Asia, Africa, the Middle East, and the like. Accordingly, the same components as in the first and second embodiments are described with the same reference numerals.
[0107]
A structure of a foundation and a floor for expansive ground countermeasures 20 of the embodiment (a floor structure for expansive ground countermeasures) C is constituted by, as shown in Fig. 8, a tubular member 20 laid on the ground surface 1a of the ground (the expansive ground) 1 that exhibits expansibility, an expansion suppressing soil layer 21 overlaid on the expansive ground 1 to bury a lower end side of the tubular member 20, a second buffer layer 22 overlaid on the expansion 25 suppressing soil layer 21, a level concrete layer 23 overlaid on the second buffer layer 22, and a floor slab 24 of a first floor formed on the level concrete layer 23.
[0108]
In addition, in the structure of the foundation and the floor for expansive ground countermeasures of the embodiment (the floor structure for expansive ground 30 countermeasures) C, the expansion suppressing soil layer 21 is formed by excavating the ground 1 to form a plurality of depressions 25, pulverizing the excavated soil obtained by excavating the ground 1 to form an expansion suppressing soil, and laying
35
the expansion suppressing soil on the ground surface 1a of the ground 1 while finishing the expansion suppressing soil to absorb the expansion pressure from the ground 1 to fill the depressions 25. That is, the expansion suppressing soil layer 21 is formed to finish the expansion suppressing soil on the depressions 25 and includes a plurality of penetration sections 21a buried in the ground 1. 5
[0109]
In addition, in the expansion suppressing soil layer 21 of the embodiment, a plurality of penetration sections are formed in rectangular block shapes and arranged at predetermined intervals. Further, the expansion suppressing soil is generated by mixing the slaked lime while pulverizing the excavated soil obtained by excavating the 10 ground.
[0110]
In addition, the tubular member 20 is a member having a substantially U-shaped (a substantially C-shaped) cross-sectional shape such as a U-shaped ditch, a corrugated half pipe, or the like, and is formed to include an opening section 20a 15 extending in an axial direction. Then, the tubular members 20 are disposed on the ground surface 1a between the plurality of depressions 25 formed in the expansive ground 1 such that the opening sections 20a are directed downward. In addition, in the embodiment, the tubular members 20 are installed in longitudinal and lateral directions in a grid shape between the neighboring penetration sections 21a in which 20 the tubular members 20 are arranged and disposed.
[0111]
Then, in the structure of the foundation and the floor for expansive ground countermeasures of the embodiment (the floor structure for expansive ground countermeasures) C, a granular material such as crushed stones or the like is laid on 25 the expansion suppressing soil layer 21 on the expansive ground 1 to form the second buffer layer 22, and the tubular member 20 is completely buried to form the level concrete layer 23 on the second buffer layer 22. In addition, in the embodiment, reinforcing bars are appropriately arranged on the level concrete layer 23, and concrete is poured to bury the reinforcing bars and form the floor slab 24 of the first floor. 30
[0112]
Next, when the floor structure C for expansive ground countermeasures of the embodiment configured as described above is constructed (in the construction method 36
of the structure of the foundation and the floor for expansive ground countermeasures of the embodiment (the floor structure for expansive ground countermeasures) C), as shown in plan view of Fig. 9A and a cross-sectional view of Fig. 9B, first, the expansive ground 1 is excavated from the ground surface 1a to form a pit, and the plurality of depressions 25 of a horizontal side a (m)×a longitudinal side b (m) and a 5 depth c (m) when seen in plan view are formed at intervals M in a lateral direction T1 and intervals N in a longitudinal direction T2 when seen in plan view (a ground pit excavation process).
[0113]
Then, the excavated soil generated through the pit excavation is pulverized. 10 Here, when the clay is excavated and pulverized, a volume of the pulverized excavated soil generally increases to about 1.3 to 1.5 times (increases in volume by 30 to 50%) the volume of the original ground (a rock mass) 1.
[0114]
In addition, in the embodiment, the slaked lime is added at 20 to 150 kg/m3 15 for each 1 m3 of the excavated soil and mixed and agitated while pulverizing the excavated soil generated through the pit excavation. Accordingly, an expansion property of the expansive ground 1 with respect to the excavated soil is eliminated/suppressed. That is, the expansion suppressing soil obtained by reforming and processing the excavated soil that exhibits expansibility is generated (an expansion 20 suppressing soil generating process/an expansion suppressing soil layer-forming process).
[0115]
Next, as shown in plan view of Fig. 10A and a cross-sectional view of Fig. 10B, the tubular members 20 such as shaped ditches, corrugated half pipes, or the like 25 are placed and arranged on the ground surface 1a of the expansive ground 1 in which the plurality of depressions 25 are formed (a tubular member installation process). Here, in the embodiment, the plurality of tubular members 20 such as the U-shaped ditches, the corrugated half pipes, or the like have the opening sections 20a, which are directed downward, and extend on the ground surface 1a between the neighboring 30 depressions 25 in the lateral direction T1 and the longitudinal direction T2 when seen in plan view. That is, the plurality of tubular members 20 are disposed to show a grid shape when seen in plan view in the embodiment as the plurality of tubular members
37
20 are arranged to surround the depressions 25 when seen in plan view while the opening sections 20a being disposed toward a lower side of the ground surface side. In addition, the tubular member 20 has a height of h (m) and a width of w (m).
[0116]
In a step of arranging the tubular members 20 including the opening sections 5 20a in this way, as shown in plan view of Fig. 11A and a cross-sectional view of Fig. 11B, the expansion suppressing soil is laid on the ground surface 1a including the depressions 25 to bury portions of lower end sides of the tubular members 20 while burying and filling the depressions 25 with the expansion suppressing soil. In addition, the upper surface of the laid expansion suppressing soil is planarized to form 10 the expansion suppressing soil layer 21 (an expansion suppressing soil layer-forming process). Here, the expansion suppressing soil layer 21 is formed by filling and laying the expansion suppressing soil in the finished state without rolling compaction/tamping. Accordingly, a function of absorbing/buffering (attenuating) the expansion pressure and ground displacement from the expansive ground 1 of the 15 lower side is applied to the expansion suppressing soil layer 21.
[0117]
Next, the crushed stones and so on are laid on the expansion suppressing soil layer 21 to form the second buffer layer 22, and the concrete is poured on the second buffer layer 22 to form the level concrete layer 23 (a buffer layer-forming process/a 20 level concrete layer-forming process). Further, in the embodiment, the concrete is poured while arranging the reinforcing bars on the level concrete layer 23 to construct the floor slab 24 of the first floor as shown in Fig. 8 (a floor slab forming process).
[0118]
Here, provided that a height of the tubular member 20 is h (m), a width is w 25 (m), a thickness of the second buffer layer 22 is y (m), and a thickness of the level concrete layer 23 is z (m), and further, as described above, a lateral dimension of the depressions 25 is a (m), a longitudinal dimension is b (m), a depth is c (m), an interval of the lateral direction T1 of the plurality of depressions 25 is M (m), and an interval of the longitudinal direction T2 is N (m), the floor structure C for expansive ground 30 countermeasures is constructed to satisfy the following Equation (3). According to Equation (3), an upper surface (an upper end section) of the tubular member 20 is substantially flush with an upper surface of the level concrete layer 23. 38
[0119]
[Equation 3]
)3(5.03.02zywwNwMcbah～
[0120]
For example, provided that a pit excavation scale is a = b = 3 m and c = 2 m, a 5 pit excavation interval is M = N = 6 m, a volume increase rate of the excavated soil formed by pulverizing the excavated soil is 30 to 50%, a width of the tubular member 20 is w = 0.3 m, a thickness of the second buffer layer 22 is y = 0.05 m, and a thickness of the level concrete layer 23 is z = 0.05 m, according to Equation (3), the height h of the tubular member 20 to be used is calculated as h = 0.27 to 0.38 (m). 10
[0121]
Here, since the volume increase rate by pulverization of the excavated soil varies according to properties of the soil, the volume increase rate may be calculated by performing a test construction in situ. In addition, the height h of the tubular member 20 should be at least h ≥ 0.2 m to attenuate the expansion of the ground 1. 15
[0122]
Then, when the structure of the foundation and the floor for expansive ground countermeasures (the floor structure for expansive ground countermeasures) C is constructed as described above, since the expansion suppressing soil layer (the backfilled layer) 21 formed between the first floor and the expansive ground 1 is 20 finished, when water such as rain water or the like comes in contact with the expansive ground 1 to generate the expansion pressure, the expansion pressure of the ground 1 can be absorbed/attenuated as the expansion suppressing soil layer 21 is compressed. Accordingly, swelling of the first floor can be prevented (suppressed). In addition, as the ground 1 that has expanded penetrates into the inside from the opening section 20a 25 under the tubular member 20, the expansion pressure of the ground 1 can also be attenuated by the tubular member 20.
[0123]
In addition, as the plurality of depressions 25 are regularly arranged on the ground and the expansion suppressing soil is filled in the depressions 25, the plurality 30 of penetration sections 21a of the expansion suppressing soil layer 21 are aligned. For this reason, when expansion occurs in the ground 1, the expansion pressure is
39
effectively absorbed/attenuated by deformation of the neighboring penetration sections 21a.
[0124]
Further, the crushed stones or the like are laid on the expansion suppressing soil layer 21 to form the second buffer layer 22 having gaps. For this reason, when 5 the expansion pressure is applied to the second buffer layer 22, the crushed stones or the like are laid to absorb/attenuate the expansion pressure using the gaps.
[0125]
Further, since the level concrete layer 23 is formed on the second buffer layer 22, the expansive force of the ground 1 can be blocked by the level concrete layer 23. 10
[0126]
Accordingly, in the structure of the foundation and the floor for expansive ground countermeasures of the embodiment, and the construction method of the structure of the foundation and the floor for expansive ground countermeasures (the floor structure C for expansive ground countermeasures and the construction method 15 of the floor structure C), the expansion pressure when the ground 1 that exhibits expansibility expands can be absorbed by the expansion suppressing soil layer 21 formed by laying the expansion suppressing soil formed through pulverization of the excavated soil on the ground surface 1a. In addition, here, since the expansion suppressing soil layer 21 includes the plurality of penetration sections 21a that 20 penetrate into the ground 1, the expansion pressure can be applied to the penetration section 21a to effectively absorb the expansion pressure. Accordingly, upheaval of the ground 1 can be effectively suppressed.
[0127]
In addition, since the tubular member 20 having the opening section 20a 25 directed downward is placed on the ground surface 1a of the ground 1 corresponding to the portion at which the penetration section 21a is not formed, the ground (expansive soil) 1 enters the tubular member 20 through the opening section 20a. Accordingly, the expansion pressure can be absorbed, and not only the expansion pressure from the ground 1 of the portion at which the penetration section 21a is not 30 formed but also the upheaval of the ground 1 can be effectively absorbed and suppressed by the tubular members 20.
[0128] 40
Further, since the second buffer layer 22 obtained by laying the granular material such as crushed stones or the like is formed on the expansion suppressing soil layer 21, the expansion pressure when the ground 1 expands is more effectively absorbed by the second buffer layer 22. In addition, since the level concrete layer 23 is formed on the second buffer layer 22, the expansion pressure of the ground 1 can be 5 blocked by the level concrete layer 23.
[0129]
Accordingly, in the structure of the foundation and the floor for expansive ground countermeasures of the embodiment, and the construction method of the structure of the foundation and the floor for expansive ground countermeasures (the 10 floor structure C for expansive ground countermeasures and the construction method of the floor structure C), the expansion suppressing soil layer 21 is formed by excavating the expansive soil of the in situ soil to be buried and leveled, for example, without rolling compaction, the second buffer layer 22 is formed by laying the granular material such as crushed stones or the like, and the level concrete is poured to form the 15 level concrete layer 23. In addition, the tubular member 20 is laid on the ground surface 1a. Accordingly, when the ground 1 that exhibits expansibility expands, the expansion pressure can be absorbed by the expansion suppressing soil layer 21, the second buffer layer 22, or the tubular member 20, and further, the expansion pressure can be blocked by the level concrete layer 23. Accordingly, generation of the 20 swelling on the first floor (the floor slab) 24 formed on the level concrete layer 23 due to the expansion of the expansive ground 1 can be prevented. According to the above-mentioned configuration and construction, expansive soil countermeasures can be effectively adopted at a low cost.
[0130] 25
In addition, since the expansion suppressing soil layer 21 that is back-filled and finished without rolling compaction and the level concrete layer 23 also function as a mold upon concrete placement of the first floor slab 24, no plywood mold, precast mold, deck plate, or the like is needed when the floating floor is constructed, and workability and reliability of the floor structure can be improved. 30
[0131]
In addition, in the structure of the foundation and the floor for expansive ground countermeasures of the embodiment, and the construction method of the 41
structure of the foundation and the floor for expansive ground countermeasures (the floor structure C for expansive ground countermeasures and the construction method of the floor structure C), since the plurality of penetration sections 21a of the expansion suppressing soil layer 21 are aligned at predetermined intervals, when the ground 1 under the structure 2 expands, the expansion pressure can be substantially 5 uniformly absorbed/attenuated by the plurality of penetration sections 21a. In addition, as the tubular members 20 are laid between the plurality of aligned penetration sections 21a to be arranged in a grid shape, the expansion pressure of the ground 1 can be substantially uniformly absorbed/attenuated by the tubular member 20. Accordingly, the expansion pressure can be more effectively absorbed. 10
[0132]
Further, as the slaked lime is mixed with the excavated soil obtained by excavating the ground 1 that exhibits expansibility, expansibility of the expansion suppressing soil (the excavated soil) can be eliminated/suppressed. Accordingly, expansion pressure of the ground 1 can be more effectively absorbed by the expansion 15 suppressing soil layer 21.
[0133]
That is, in the structure of the foundation and the floor for expansive ground countermeasures of the embodiment (the floor structure for expansive ground countermeasures) C, the slaked lime is added to the excavated soil that exhibits 20 expansibility in situ at 20 to 150 kg for each 1 m3 of the excavated soil to be mixed and agitated to form the expansion suppressing soil. For this reason, similar to the above-mentioned description, expansibility of the excavated soil is eliminated/suppressed by Ca2+ of the slaked lime. Accordingly, when the rain water intrudes into the ground 1, the expansion suppressing soil does not expand and can reliably absorb/attenuate the 25 expansion pressure of the ground 1.
[0134]
Further, the expansion suppressing soil generated in this way is laid between the ground 1 that exhibits expansibility and the structure 2 to form the expansion suppressing soil layer 21. For this reason, when the water intrudes into the ground 1 30 under the structure 2, Ca2+ (calcium) is eluted from the slaked lime mixed with the in situ soil while the water comes in contact with the expansion suppressing soil layer 21. Accordingly, Ca2+ can come in contact with the ground 1 that exhibits the swelling
42
property such as montmorillonite or the like together with the water. Then, for example, as Ca2+ comes in contact with the Na type montmorillonite, Na+ between the unit crystal layers can be substituted with Ca2+ to be varied into a Ca type. That is, the ground 1 that exhibits expansibility can be automatically changed into ground having extremely little expansibility. 5
[0135]
Further, as the water comes in contact with the slaked lime of the expansion suppressing soil layer, the pH of the water is increased to become alkaline. Specifically, the pH of the water can be maximally increased to pH 12.4 when it comes in contact with the slaked lime. 10
In addition, for example, the montmorillonite disappeared or changes into calcium aluminate hydrate (CAH) or calcium silicate hydrate (CSH) when it comes in contact with a calcium solution (alkaline water) with a pH of 11 or more.
[0136]
For this reason, in the structure of the foundation and the floor for expansive 15 ground countermeasures of the embodiment (the floor structure for expansive ground countermeasures) C, when the water intrudes into the ground 1 under the structure 2, the pH is increased while the water (rain water) comes in contact with the slaked lime of the expansion suppressing soil layer 21, and the alkaline water having the increased pH can come in contact with the ground 1 that exhibits the swelling property such as 20 montmorillonite or the like. Then, for example, as the alkaline water with the pH of 11 or more (the rain water having the increased pH) comes in contact with the montmorillonite, the ground 1 that exhibits expansibility can be automatically changed into ground 1 having extremely little expansibility.
[0137] 25
Accordingly, according to the structure of the foundation and the floor for expansive ground countermeasures of the embodiment, and the construction method of the structure of the foundation and the floor for expansive ground countermeasures (the floor structure C for expansive ground countermeasures and the construction method of the floor structure C), as the slaked lime is included in the expansion 30 suppressing soil layer 21 formed between the ground 1 that exhibits expansibility and the structure 2, even when the water intrudes into the ground 1, properties of the ground 1 that exhibits expansibility are varied, and generation of the expansion 43
pressure can be suppressed.
[0138]
Further, as the expansion suppressing soil layer 21 includes the penetration section 21a that penetrates into the expansive ground, the pH of the water intruding into the ground 1 is increased, the alkalinized water more reliably comes in contact 5 with the ground 1, properties of the ground 1 that exhibits expansibility can be varied, and generation of the expansion pressure can be suppressed.
[0139]
While the third embodiment of the structure of the foundation and the floor for expansive ground countermeasures according to the present invention and the 10 construction method of the structure of the foundation and the floor for expansive ground countermeasures have been described above, the present invention is not limited to the third embodiment but may be appropriately modified without departing from the spirit of the present invention.
[0140] 15
For example, the structure of the foundation and the floor for expansive ground countermeasures according to the present invention and the construction method of the structure of the foundation and the floor for expansive ground countermeasures (the floor structure for expansive ground countermeasures and the construction method of the floor structure) may be applied to all structure types of the 20 floor such as a dirt floor form, a structure slab type, or the like.
[0141]
Next, a structure of a foundation and a floor for expansive ground countermeasures according to a fourth embodiment of the present invention will be described with reference to Figs. 13A to 21. Here, the embodiment relates to a 25 structure of a foundation for expansive ground countermeasures configured for constructing a structure such as a building or the like on expansive soil (ground that exhibits expansibility) including clay minerals having expansibility such as montmorillonite or the like which occupy wide ranges of arid and quasi-arid areas, for example, Southeast Asia, Africa, the Middle East, and the like. Accordingly, the 30 same components as in the first, second and third embodiments are described with the same reference numerals.
[0142] 44
A structure of a foundation and a floor for expansive ground countermeasures of the embodiment (a floor structure for expansive ground countermeasures) D is configured to include, as shown in Figs. 13A, 13B, 14A and 14B, a ditch 30 formed by excavating the ground surface 1a of the ground (the expansive ground) 1 that exhibits expansibility, a first buffer layer 31 obtained by filling/laying the granular material 5 such as crushed stones or the like in the ditch 30 or the ditch 30 and the ground surface 1a, and a floor slab (a dirt floor) 32 of a first floor overlaid on the first buffer layer 31.
[0143]
In addition, as shown in Figs. 15 and 16 or 17 to 19, the expansion suppressing soil layer 21 is formed by excavating the ground 1 to form the ditch 30 10 extending in one direction T2 or the ditch 30 in a grid shape when seen in plan view, and filling the granular material such as crushed stones or the like in the ditch 30.
[0144]
Further, in the embodiment, provided that an excavation width in a lateral direction (the other direction) T1 when seen in plan view is a, an excavation width in a 15 longitudinal direction (one direction) T2 is d (in the case of the grid shape), an excavation depth of the ditch is c, an interval of the ditch 30 in the lateral direction T1 is M, and an interval of the ditch 30 in the longitudinal direction T2 is N (in the case of the grid shape), the ditch 30 is formed to satisfy a ≥ 0.5 m, d ≥ 0.5 m, c ≥ 0.5 m, M ≤ 5c + a, and N ≤ 5c + d. 20
[0145]
In addition, for example, crushed stones such as limestone or the like having a particle diameter D50 of 20 mm or more when a transmission mass percentage obtained by particle size distribution is 50% may be used as the granular material. Then, as shown in Figs. 14A and 14B, the granular material is filled/laid in the ditch 30, 25 or the ditch 30 and the ground surface 1a, and a surface level of the first buffer layer 31 is higher than a ground surface level of the original ground 1. In addition, the input granular material may be rolled and compacted to smoothly level the surface of the first buffer layer 31 such that later processes in construction work of the structure 2 become easy. 30
[0146]
Then, in the structure of the foundation and the floor for expansive ground countermeasures of the embodiment (the floor structure for expansive ground
45
countermeasures) D, in a step of forming the ditch 30 and filling/laying the granular material to form the first buffer layer 31 in this way, as shown in Figs. 13A and 13B, the floor slab 32 and a building foundation 5 are constructed.
[0147]
Here, Fig. 20 is “a result obtained by comparing expansion pressures in a 5 vertical direction in expansion pressure tests under different conditions” disclosed in “Shahid Azam (2006): Large-scale odometer for assessing swelling and consolidation behavior of Al-Qatifclay, Expansive soils, Taylor & Francis, edited by Amer Ali Al-Rawas & Mattheus F. A. Goosen.”
[0148] 10
In the expansion pressure test, the expansive soil is collected without being mixed and taken to a soil test room.
1) A soil quality sample is formed in a flat columnar shape having a diameter of 7 cm and a height of 2 cm, the soil quality sample is packed in a mold having extremely high stiffness in a horizontal direction, and a pressure in a vertical direction 15 upon water intrusion/expansion is measured.
2) A soil quality sample is formed in a flat rectangular parallelepiped having one side of 30 cm and a height of 8.5 cm, the soil quality sample is packed in a mold having low stiffness in the horizontal direction, and a pressure in the vertical direction upon water intrusion/expansion is measured. 20
[0149]
That is, in the soil test of the above-mentioned paragraph 1), the expansion pressure in the vertical direction under the condition in which the soil quality sample cannot be displaced (expanded) in the horizontal direction is measured, and in the soil test of the above-mentioned paragraph 2), the expansion pressure in the vertical 25 direction under the condition in which the soil quality sample is slightly displaced (expanded) in the horizontal direction is measured.
[0150]
As shown in Fig. 20, in the soil test of the above-mentioned paragraph 1), the expansion pressure in the vertical direction was 550 kPa, whereas, in the soil test of the 30 above-mentioned paragraph 2), the expansion pressure in the vertical direction was 200 kPa. That is, from the result, it was confirmed that, when the displacement occurs in the horizontal direction, the expansion pressure is 1/2 that in the vertical
46
direction or less. Here, in a sample size of the soil test of the above-mentioned paragraph 2 has one side is 30 cm and is height of 8.5 cm, and thus a ratio of width/height of the sample is 30/8.5 = 3.5.
[0151]
Based on this, as described in the embodiment, when the ground 1 that 5 exhibits expansibility is excavated to form the ditch 30 extending in one direction or the ditch 30 in the grid shape and the granular material is filled in the ditch 30 to form the first buffer layer 31, as shown in Fig. 21, the expansive soil penetrates into the gaps of the granular material of the first buffer layer 31 when the expansive ground 1 expands, displacement in the horizontal direction is allowed by the first buffer layer 31, 10 and as a result, the expansion pressure in the vertical direction can be reduced.
[0152]
Accordingly, in the structure of the foundation and the floor for expansive ground countermeasures of the embodiment (the floor structure for expansive ground countermeasures) D, the expansive soil of the in situ soil is excavated to form the ditch 15 30 extending in one direction T2 or the ditch 30 in the grid shape when seen in plan view, the granular material such as crushed stones or the like is filled in the ditch 30 to form the first buffer layer 31, and the floor slab 32 is formed on the first buffer layer 31. Accordingly, when the ground 1 that exhibits expansibility expands, the expansion pressure can be absorbed by the first buffer layer 31, and as the granular 20 material is filled in the ditch 30 to form the first buffer layer 31, the expansion pressure in the vertical direction can be effectively absorbed. Accordingly, the swelling in the first floor (the floor slab 32) on the first buffer layer 31 due to expansion of the expansive ground 1 can be prevented. According to the above-mentioned configuration and construction, effective expansive soil countermeasures can be 25 adopted at a low cost.
[0153]
In addition, as a substance having the particle diameter D50 of 20 mm or more when the transmission mass percentage is 50% (crushed stones or the like) is used as the granular material that fills the ditch 30, even when the displacement in the 30 horizontal direction of the expansive ground 1 is allowed by the first buffer layer 31, the expansion pressure in the horizontal direction and the vertical direction can be appropriately reduced without earth and sand falling into the ditch 30. 47
[0154]
Further, provided that an excavation width in the other direction T2 perpendicular to the one direction T2 when seen in plan view is a, an excavation width in the one direction T2 when the ditch 30 is formed in the grid shape is d, an excavation depth of the ditch 30 is c, an interval of the ditch 30 in the other direction 5 T1 is M, and an interval of the ditch 30 in the one direction T2 when the ditch 30 is formed in the grid shape is N, when not only the ditch 30 but also the first buffer layer 31 are formed to satisfy a ≥ 0.5 m, d ≥ 0.5 m, c ≥ 0.5 m, M ≤ 5c + a, and N ≤ 5c + d, a ratio of width/height (M−a)/c of a residual section (protrusion) of the ground 1 protruding while forming the ditch 30 is 5 or less. Accordingly, when expansion 10 occurs in the ground 1 that exhibits expansibility, the expansion pressure, in particular, the expansion pressure in the vertical direction, can be more reliably and effectively absorbed by the first buffer layer 31.
[0155]
While the fourth embodiment of the structure of the foundation and the floor 15 for expansive ground countermeasures according to the present invention has been described above, the present invention is not limited to the fourth embodiment but may be appropriately modified without departing from the spirit of the present invention.
[0156]
For example, the structure of the foundation and the floor for expansive 20 ground countermeasures according to the present invention (the floor structure for expansive ground countermeasures) may be applied to all floor structure types such as a dirt floor form, a structure slab type, or the like.
[0157]
In addition, the structure of the foundation and the floor for expansive ground 25 countermeasures of the embodiment (the floor structure for expansive ground countermeasures) D is not installed immediately under the entire structure 2, but as shown in Figs. 4A, 4B, 5 and 6, when seen in plan view, may be applied to a region of the outer circumferential section side of the structure 2 (the outer circumferential region S1). Then, as the floor structure D of the embodiment is applied to the outer 30 circumferential region S1 of the structure 2 in which intrusion of the rain water into the ground 1 and evaporation of the soil moisture from the ground surface 1a are likely to occur, and expansion of the ground 1 and sinking of the ground 1 are likely to occur,
48
effects thereof can be sufficiently exhibited.
[0158]
In the structure of the foundation and the floor for expansive ground countermeasures, and the construction method of the structure of the foundation and the floor for expansive ground countermeasures, in comparison with the related art, 5 expansive soil countermeasures having an inexpensive structure can be adopted, and expansive soil countermeasures having high reliability can be beneficially realized.
[Industrial Applicability]
[0159]
The structure of the foundation and the floor for expansive ground 10 countermeasures of the present invention can reliably achieve expansive soil countermeasures having high reliability.
[Reference Signs List]
[0160]
1 ground (expansive soil) that exhibits expansibility 15
1a ground surface (earth surface section)
1b internal ground
1c external ground
2 structure
2a outer circumferential edge (outer circumferential section, outer wall surface) 20
3 high quality soil
4 high quality ground (support layer) that does not exhibits expansibility
5 stake
6 jig
7 floating floor (structure floor) 25
10 water-shielding structure section
11 ground reform-processed section
12 third buffer layer
13 protective layer (geotextile (geosynthetic) or waterproof sheet)
14 solidification-processed soil layer 30
15 level concrete layer
16 ventilation pipe
17 stake foundation 49
18 direct foundation
20 tubular member
20a opening section
21 expansion suppressing soil layer
21a penetration section 5
22 second buffer layer
23 level concrete layer
24 floor slab
25 depression
30 ditch 10
31 first buffer layer
32 floor slab
A structure of foundation and floor for expansive ground countermeasures (foundation structure for expansive ground countermeasures)
B structure of foundation and floor for expansive ground countermeasures 15 (foundation structure for expansive ground countermeasures)
C structure of foundation and floor for expansive ground countermeasures (floor structure for expansive ground countermeasures)
D structure of foundation and floor for expansive ground countermeasures (floor structure for expansive ground countermeasures) 20
S1 outer circumferential region
S2 internal region
T1 lateral direction (other direction)
T2 longitudinal direction (one direction)

We Claim:
[Claim 1]
A structure of a foundation and a floor for expansive ground countermeasures of a structure constructed on ground that exhibits expansibility, the structure of the foundation and the floor for expansive ground countermeasures comprising: 5
a first buffer layer formed by filling a granular material in a ditch extending in one direction or a ditch formed in a grid shape when seen in plan view, which is formed by excavating the ground, or a first buffer layer formed by laying the granular material on the ground while filling the granular material in the ditch; and
a floor slab formed on the first buffer layer and the ground. 10
[Claim 2]
The structure of the foundation and the floor for expansive ground countermeasures according to Claim 1, wherein a particle diameter D50 of the granular material when a transmission mass percentage obtained by particle size distribution is 50% is 20 mm or more. 15
[Claim 3]
The structure of the foundation and the floor for expansive ground countermeasures according to Claim 1, wherein, provided that an excavation width in another direction perpendicular to the one direction when seen in plan view is a, an excavation width of the one direction when the ditch is formed in the grid shape is d, 20 an excavation depth of the ditch is c, an interval of the ditch in the other direction is M, and an interval of the ditch in the one direction when the ditch is formed in the grid shape is N, the ditch is formed to satisfy a ≥ 0.5 m, d ≥ 0.5 m, c ≥ 0.5 m, M ≤ 5c + a, and N ≤ 5c + d.
[Claim 4] 25
A structure of a foundation and a floor for expansive ground countermeasures of a surface constructed on ground that exhibits expansibility, the structure of the foundation and the floor for expansive ground countermeasures comprising:
a tubular member formed in a substantially U-shaped cross section, placed on a ground surface of the ground, and having an opening section directed downward; 30
an expansion suppressing soil layer laid on the ground surface of the ground while burying at least a portion of the tubular member;
a second buffer layer overlaid by laying a granular material on the expansion 51
suppressing soil layer;
a level concrete layer overlaid by pouring concrete on the second buffer layer; and
a floor slab formed on the level concrete layer,
wherein the expansion suppressing soil layer is formed to include a plurality 5 of penetration sections in which expansion suppressing soil penetrates into the ground by excavating the ground to form a plurality of depressions, pulverizing the excavated soil obtained by excavating the ground to generate the expansion suppressing soil, and laying the expansion suppressing soil on the ground surface of the ground while finishing the expansion suppressing soil to absorb an expansion pressure from the 10 ground to fill the depressions.
[Claim 5]
The structure of the foundation and the floor for expansive ground countermeasures according to Claim 4, wherein the plurality of penetration sections are aligned at predetermined intervals, and 15
the tubular members are laid on the ground surface between the neighboring penetration sections to be arranged in a grid shape.
[Claim 6]
The structure of the foundation and the floor for expansive ground countermeasures according to Claim 4, wherein the expansion suppressing soil is 20 generated by mixing slaked lime while pulverizing the excavated soil obtained by excavating the ground.
[Claim 7]
A method of constructing a structure of a foundation and a floor for expansive ground countermeasures of a structure on ground that exhibits expansibility, the 25 construction method of the structure of the foundation and the floor for expansive ground countermeasures comprising:
a ground pit excavation process of excavating the ground to form a plurality of depressions;
a tubular member installation process of placing a tubular member formed in a 30 substantially U-shaped cross section on the ground surface of the ground such that an opening section is directed downward;
an expansion suppressing soil layer-forming process of pulverizing the 52
excavated soil obtained through the ground pit excavation process to generate expansion suppressing soil, and laying the expansion suppressing soil on the ground surface of the ground to form an expansion suppressing soil layer while finishing the expansion suppressing soil to absorb an expansion pressure from the ground to fill the depressions; 5
a buffer layer-forming process of laying a granular material over the expansion suppressing soil layer to form a second buffer layer;
a level concrete layer-forming process of pouring concrete over the second buffer layer to overlay and form a level concrete layer; and
a floor slab forming process of forming a floor slab on the level concrete layer. 10
[Claim 8]
The construction method of the floor structure for expansive ground countermeasures according to Claim 7, comprising an expansion suppressing soil generating process of mixing slaked lime while pulverizing the excavated soil obtained through the ground pit excavation process to generate an expansion suppressing soil. 15
[Claim 9]
A structure of a foundation and a floor for expansive ground countermeasures for constructing a structure on ground that exhibits expansibility upon coming in contact with water, the structure of the foundation and the floor for expansive ground countermeasures constituted by an outer circumferential region of an outer 20 circumferential section side of the structure serving as a stake foundation, and an internal region inside the outer circumferential region serving as a direct foundation.
[Claim 10]
The structure of the foundation and the floor for expansive ground countermeasures according to Claim 9, wherein a distance X from an outer 25 circumferential edge to the internal region of the structure is set to the larger value between
a distance X = a coefficient of permeability k of the ground×a period t1 in which water comes in continuous or intermittent contact with the ground and the ground continuously or intermittently expands, and 30
a distance X = a coefficient of permeability k of the ground×a period t2 in which water is continuously not in contact with the ground to a certain extent or more.
[Claim 11] 53
A foundation structure for expansive ground countermeasures for constructing a structure on ground that exhibits expansibility, the structure of the foundation and the floor for expansive ground countermeasures comprising:
a water-shielding structure section continuously formed to surround the structure when seen in plan view and extending to a predetermined depth from the 5 ground surface; and
a ground reform-processed section formed by reforming and processing the ground of a predetermined depth range from the ground surface at a portion surrounded by the water-shielding structure section,
wherein a ground depth at which expansion due to contact with water 10 penetrating into the ground and contraction due to drying are repeated is specified, and the water-shielding structure section is formed to penetrate to at least the specified ground depth at which the expansion and the contraction are repeated.
[Claim 12]
The structure of the foundation and the floor for expansive ground 15 countermeasures according to Claim 11, wherein at least one investigation and/or test of literature/document investigation, in situ ground investigation, and a soil test of a soil sample collected from the ground is performed to specify the specified ground depth at which the expansion and the contraction are repeated, and the water-shielding structure section is formed. 20
[Claim 13]
The structure of the foundation and the floor for expansive ground countermeasures according to Claim 11, wherein moisture weight percentages of the ground in a rainy period and a dry period are measured at a plurality of places from the ground surface in the depth direction, and the water-shielding structure section is 25 formed to penetrate to at least the specified ground depth at which a difference between the moisture weight percentages in a rainy period and the dry period is smaller than a preset value at which the structure is not harmed by expansion in a rainy period.
[Claim 14] 30
The structure of the foundation and the floor for expansive ground countermeasures according to Claim 11, wherein the ground reform-processed section comprises a third buffer layer formed by excavating internal ground surrounded by the 54
water-shielding structure section from the ground surface and spreading a filler having a particle diameter of an order of several cm to tens cm, a protective layer formed of a sheet-shaped member laid on the third buffer layer and configured to protect the third buffer layer, and a solidification-processed soil layer formed by rolling and compacting a mixed soil mixed with cement or lime on the protective layer. 5
[Claim 15]
The structure of the foundation and the floor for expansive ground countermeasures according to Claim 14, wherein the sheet-shaped member is a geosynthetic or waterproof sheet.
[Claim 16] 10
The structure of the foundation and the floor for expansive ground countermeasures according to Claim 11, wherein the water-shielding structure section is formed to penetrate to at least the specified ground depth at which a difference between the moisture weight percentages in a rainy period and the dry period is 5% or less. 15
[Claim 17]
The structure of the foundation and the floor for expansive ground countermeasures according to Claim 11, wherein the ground reform-processed section comprises a level concrete layer formed by pouring concrete on the solidification-processed soil layer. 20
[Claim 18]
The structure of the foundation and the floor for expansive ground countermeasures according to Claim 14, wherein the ground reform-processed section comprises a ventilation pipe reaching from the ground surface to the third buffer layer.
[Claim 19] 25
The structure of the foundation and the floor for expansive ground countermeasures according to Claim 15, wherein the ground reform-processed section comprises a ventilation pipe reaching from the ground surface to the third buffer layer.
[Claim 20]
The structure of the foundation and the floor for expansive ground 30 countermeasures according to Claim 16, wherein the ground reform-processed section comprises a ventilation pipe reaching from the ground surface to the third buffer layer.
[Claim 21] 55
The structure of the foundation and the floor for expansive ground countermeasures according to Claim 17, wherein the ground reform-processed section comprises a ventilation pipe reaching from the ground surface to the third buffer layer.
[Claim 22]
A method of constructing a structure of a foundation and a floor for expansive 5 ground countermeasures for constructing a structure on ground that exhibits expansibility, the construction method of the structure of the foundation and the floor for expansive ground countermeasures comprising:
a specified ground depth investigation process of specifying a ground depth at which expansion due to contact with water that has intruded into the ground and 10 contraction due to drying are repeated;
a water-shielding structure section-forming process of forming a water-shielding structure section continuously formed to surround the structure when seen in plan view and penetrating from the ground surface to at least the ground depth specified in the specified ground depth investigation process; 15
a buffer layer-forming process of forming a third buffer layer by excavating internal ground surrounded by the water-shielding structure section from the ground surface and spreading a filler having a particle diameter of an order of several cm to tens of cm;
a protective layer-forming process of forming a protective layer by laying a 20 sheet-shaped member on the third buffer layer to protect the third buffer layer; and
a solidification-processed soil layer-forming process of forming a solidification-processed soil layer on the protective layer by mixing cement or lime and rolling and compacting the mixed soil.
[Claim 23] 25
The construction method of the structure of the foundation and the floor for expansive ground countermeasures according to Claim 22, wherein, in the specified ground depth investigation process, at least one investigation and/or test of literature/document investigation, in situ ground investigation, and a soil test of a soil sample collected from the ground is performed to specify the specified ground depth at 30 which the expansion and the contraction are repeated.
[Claim 24]
The construction method of the structure of the foundation and the floor for
56
expansive ground countermeasures according to Claim 22, wherein the specified ground depth investigation process comprises a ground investigation process of measuring moisture weight percentages in a rainy period and a dry period of the ground that exhibits expansibility at a plurality of places from the ground surface in a depth direction, and a water-shielding structure section depth determination process of 5 obtaining a difference between the moisture weight percentage in a rainy period and the moisture weight percentage in the dry period of the ground and specifying a ground depth at which the surface is not harmed by expansion in a rainy period.