FIELD OF THE INVENTION
The present invention relates to a method for ground improvement. More specifically, the invention relates to a time saving and efficient method of soil consolidation using an effective chemical grouting technique for strengthening the load bearing capacity of the soil and preventing any kind of injuries/accidents to any equipment or property.

BACKGROUND OF THE INVENTION
In earlier times, people preferred living near water bodies as water is one of the basic needs for dwelling and there was a lack of water supply mechanism. With time, development took place in every sector such as houses that were made of wood are now made with bricks and mortar. The civil construction sector developed a lot to deliver safe and robust constructions capable of encountering even the worst of natural calamities such as earthquakes, cyclones, floods etc.
The construction sites located near the water bodies must focus on developing a strong foundation for strengthening the load bearing capacity of the soil layer and prevent the situations of underground water connections of water tables with water bodies such as a river stream, ocean etc. and development of cracks in the walls of the buildings.
In order to strengthen the foundation of buildings a thorough investigation of soil is very necessary. Based on soil conditions a suitable type of foundation is laid such as spread footings and wall footings, mat foundations, pile foundations and drilled shafts. Even after investigating the soil conditions, one may go wrong in estimations and also with time the soil conditions change which result in loss of strength to the foundations. In such cases, strengthening of an existing foundation is required. Generally, underpinning technique is used for strengthening an existing foundation or building wherein the foundation is extended in depth or breadth to provide support and distribution of load across a greater area using micropiles and grouting.
Generally, the building constructions in areas which are already dwelled up at shorter distances such as 150-200 m from water bodies have water table present at shallow depths such as 3-4 m from the surface and grouting is done to strengthen the foundations in these conditions. These constructions are always at risk of developing underground water connections of the water table with water bodies such as river streams etc. which may cause wash out of the chemicals/grouting material even before it consolidates the soil strata. This consequently adds up in quantities of material to consolidate the same soil mass as compared to the relatively less watery soil conditions.
The generally known grouting techniques though prevent water channel formation underground but proves ineffective in consolidation of an existing building foundation. US3103235A discloses a sleeve packer for performing a chemical grouting operation in a sub-surface conduit. The principal object of the invention is to provide a packer that lends itself to use with fast-gelling grouts of this kind, particularly a sleeve packer that is at once simple, sturdy, leak-proof and not given to clogging as a result of premature gelling of the chemicals within the packer.
Therefore, technological development is needed in foundation strengthening techniques applicable particularly in areas dwelled in closeness with water bodies and have a shallow water table to increase the load bearing capacity of the soil and prevent wash out of foundation material and cracks in foundation.

OBJECT OF THE INVENTION
The main object of this invention is to provide a method of soil consolidation to strengthen the load bearing capacity using appropriate chemical grouting.
Another object of the present invention is to provide a method of soil consolidation particularly for areas dwelled up at shorter distances such as 150-200 m from water bodies have water table present at shallow depths such as 3-4 m from the surface.
Yet another object of the present invention is consolidation of the soil mass with appropriate chemicals below the foundation of a building to protect it from sinking & breaking and consequently developing cracks in the walls of the building.
Yet another object of the present invention is to reduce or eliminate the risk of underground water connections of the water table with the water bodies such as river stream.
Yet another object of the present invention is to carry out chemical grouting/injection for consolidation of the soil below the foundation of the building.
Yet another object of the present invention is to reduce the permeability of soil below foundation and thereby increasing the in-situ bearing capacity of soil.
Yet another object of the present invention is to carry out the grouting process in stages in every borehole starting from the bottom most part of the borehole using perforated casing pipes and placing inflatable packers at suitable intervals.
Yet another object of the present invention is to drill inner and outer grout holes in a way to avoid damages to the foundation of the building.

SUMMARY OF THE INVENTION
The present invention provides an efficient and time saving method of consolidation of soil mass through appropriate chemical grouting for areas dwelled up at shorter distances such as 150-200 m from water bodies and have water table present at shallow depths such as 3-4 m from the surface to prevent any risk of underground water connections of the water table with the water bodies and damage to the foundation.
In the main embodiment of the present invention, the method of soil consolidation for existing building foundation through chemical grouting for areas dwelled up at shorter distances from water bodies and water table present at shallow depths comprises of: curtain grouting along an outer area of the foundation wall; structural grouting for consolidating soil of the building foundation; and reinforcing soil with grout carrying medium below the foundation.
Here, curtain grouting along an outer area of the foundation wall comprises of: cementing along the grouting area i.e. from the edge of the foundation wall upto a predefined distance for preventing penetration of water through sources such as rain; settling down micropiles of predefined length; drilling plurality of holes using steel casing of defined length; inserting the pipes with perforations i.e. grout carrying medium and lifting the steel casing upto a predefined height from ground level; placing reusable inflatable packer at a distance below ground level; injecting a predefined chemical with varied pressure for pumping said chemical; stopping chemical injection when specified chemical quantity for hole is reached; removing packer and sealing the hole.
Further, structural grouting for consolidating soil of the building foundation comprises of: drilling boreholes of predefined diameter at a particular angle ranging from vertical for grouting from outside & inside of the building using standard drilling machines; grouting in stages in every borehole starting from bottom most part of the borehole using perforated casing pipes i.e. grout carrying medium and placing inflatable packers at suitable intervals; injecting chemicals in bottom section in two stages with different pressure for effective soil consolidation even below the foundation of the building. Further, once the grouting is completed in the bottom most section, another packer will be placed at a particular distance from previous packer and grouting operation will be carried out in the similar fashion. One packer near the surface is used for completing the grouting injection process in the remaining part of the borehole.
Furthermore, reinforcing soil with grout carrying medium below the foundation comprises of: installing the grout carrying medium from the outside and inside the building in the intermediate points of the structural injection holes at defined intervals in the inclined way upto the central axis of the foundation; injecting chemical through grout carrying medium until a varied pressure is achieved.
Hence, the proposed method of soil consolidation below the foundation in areas dwelled up at shorter distances from water bodies and water table present at shallow depths efficiently prevents the foundation from any damage and reduces the time taken for consolidation.

BRIEF DESCRIPTION OF THE DRAWING
A complete understanding of the method of the present invention may be obtained by reference to the following drawings:
Figure 1 elucidates cross sectional view of curtain grout holes according to an embodiment of the present invention;
Figure 2 elucidates cross sectional view of structural grout holes below the foundation according to an embodiment of the present invention;
Figure 3 elucidates schematic diagram showing the grouting pattern at angular structural area according to an embodiment of the present invention;
Figure 4 elucidates schematic diagram showing the grouting pattern in straight wall area according to an embodiment of the present invention;
Figure 5 elucidates cross sectional view of the soil reinforcement with grout carrying medium according to an embodiment of the present invention;
Figure 6 elucidates plan view of curtain grout holes, structural grout holes and reinforcement holes with grout carrying medium; and
Figure 7 elucidates inflated packers assembly according to an embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION
The present invention will now be described more fully hereinafter with reference to the accompanying drawings in which a preferred embodiment of the invention is shown. This invention may, however, be embodied in many different forms and should not be construed as being limited to the embodiment set forth herein. Rather, the embodiment is provided so that this disclosure will be thorough, and will fully convey the scope of the invention to those skilled in the art.
In an embodiment of the present invention, the soil investigation for areas close to water bodies with shallow water table discloses that the stratigraphy is variable and the entire subsurface soil mass shall be divided in five stratums for upto borehole termination depth of 25 meters. The top surface column upto an average depth of 5 meters is filled up with soil from rubbish & brickbats and followed by the columns mostly consisting of clay, clayey silt/silty clay, organic matter/decomposed wood and sand/sandy silt. Also, a borehole analysis highlights that the top most stratum, consists of heterogeneous filling with rubbish and brickbats. The second stratum column consists of clayey silt/silty clay with organic matter and decomposed wood extending down to a uniform depth of 15 meters from surface below the entire structure.
In another embodiment of the present invention, due to the soil conditions a continuous water drainage during the grouting operations is proposed using pumping at the project site or alternatively using additional chemicals for isolating/curtaining/freezing the underneath strata in the affected area before the consolidation treatment. Also, consolidation of top stratum is required, which is filled up with rubbish and brickbats, upto an average depth of 5-6 meters from surface beneath the foundation wall of the structure so as to strengthen the load bearing capacity of the strata.
In the main embodiment of the present invention, a method of soil consolidation for existing building foundation through chemical grouting for areas dwelled up at shorter distances from water bodies and water table present at shallow depths comprises of: curtain grouting along an outer area of a foundation wall; structural grouting for consolidating soil of the building foundation; and reinforcing soil with grout carrying medium below the foundation. Therefore, a method of soil consolidation for an existing building foundation located nearby water bodies comprising steps of: A) curtain grouting along an outer area (13) of a foundation wall (12); B) structural grouting for consolidating soil of the building foundation; and C) reinforcing soil with grout carrying medium (15) below the foundation.
Figure 1 elucidates cross sectional view of curtain grout holes and curtain grouting of step A) comprises the steps of:
a) cementing said foundation wall (12) to prevent any penetration of water;
b) settling plurality of micro-piles (10) at a distance from said foundation wall (12);
c) drilling a plurality of vertical holes (11) at 0.1 meter to 3 meter distance from said foundation wall (12) using steel/PVC casings;
d) inserting plurality of grout carrying medium in holes (11) drilled in step b) and uplifting said steel/PVC casing upto 5 meter height from ground level (19) from holes (11) drilled in step b);
e) placing a reusable inflatable packer (18) at 0.5 meter to 5 meter distance below ground level (19) inside said grout carrying medium inserted in step c);
f) injecting a predefined grouting chemical with varied pressure for pumping of said grouting chemical inside said pipe using grout pumps (17) after packer (18) is placed in step d);
g) stopping chemical injection of step f) when specified chemical quantity for hole (11) drilled in step a) is reached; and
h) removing packer after chemical injection stopped in step f) and sealing the hole (11) drilled in step a).
The cementing of said foundation wall (12) is done using Portland cement concrete of M20 grade. The curtain grouting is done with preferably a resin based chemical. Plurality of grout carrying medium used in curtain grouting are PVC pipes with perforations and covered by rubber tubes to prevent soil or any other material to pass through the perforation.
Figure 2 elucidates cross sectional view of structural grout holes and structural grouting of step B) comprises the steps of:
a) drilling a plurality of 15 degree to 150 degree inclined boreholes (16) at 1 meter to 10 meter distance from foundation wall (12) at predefined angles for grouting from outside (13) & inside (14) of the building using standard drilling machines;
b) grouting in stages in said borehole (16) drilled at step a) starting from bottom of said borehole (16) using grout carrying medium and placing inflatable packers (18) at suitable intervals;
c) injecting a predefined grouting material in said borehole (16) after inflatable packers (18) are placed in step b) with varied pressure; and
d) grouting at ground level (19) for completing the chemical injection in step c) in said borehole (16).
The structural grouting for consolidating soil of the building foundation is carried out in angular structure area such as intersection of walls i.e. corners of a building as well as straight wall areas which is area left out after completing angular area. The structural grouting in angular structural area as depicted in Figure 3 comprises of chemical grouting at opposite locations of the angle simultaneously i.e. at the same time from the intersection point of the corner of the building in a pattern at predefined distance intervals such as at 1 m, 2 m, 3 m respectively. Such consolidation done following a pattern to drain out the water that is captured in soil and sequentially drained restricting the re-entry of water towards the foundation. At angular structural areas the angle space will be locked preventing any damage to the structure. The structural grouting is carried in stages starting from the bottom to top of the holes (16) with a waiting time of 20-30 mins for each section for setting up the chemical. Grout carrying medium used in structural grouting are PVC pipes with perforations.
In straight wall areas, structural grouting is done in a similar pattern as in angular structural area as depicted in Figure 4. The straight wall area the pattern is created by dividing the length of the area by its centre and grouting at both sides in a pattern at predefined distance intervals such as 1 m on opposite sides. With this pattern, water is drained in a sequential way by keeping the soil with full bearing and dry.
Figure 5 elucidates cross sectional view of the soil reinforcement with grout carrying medium and the reinforcing soil in step C) comprises the steps of:
a) installing plurality of grout carrying medium (15) at predefined inclined angle from outside (13) and inside (14) of the building in the intermediate points of the boreholes (16) of structural grouting in step B) at defined intervals upto central axis of the foundation wall (12); and
b) injecting a predefined chemical along with said grout carrying medium (15) installed in step a) until a varied pressure is achieved.
Grout carrying medium used in soil reinforcement in step C) include but not limited to PVC pipes with perforations or sacrificial anchor bars.
Figure 6 elucidates plan view of curtain grout holes (11), structural grout holes (16) and reinforcement holes with grout carrying medium (15). The micro piles (10), curtain grout holes (11), structural grout holes (16) and grout carrying medium (15) are made alternatively such that the quantity of grout used is minimum.
Figure 7 elucidates inflated packers assembly comprising of a packer (18) and a grouting pump (17). The grouting pumps used are GX 45 PU-N and GX 30.
Here, the inner and outer grout holes are drilled to avoid any damage to foundation and in consideration with the grouting requirements in the top stratum of an average depth of 5-6 meters and the additional supportive width of 1.2 meter inside the building & upto a distance to the pilling line outside the building without affecting the foundation. Also, grout hole spacing is decided considering the grouting area of influence, which usually depends on chemical properties and site conditions, to cover the consolidation of maximum soil mass below and near the foundation wall in the adjacent grout holes leaving no unconsolidated area. The grouting methodology specifications are given below in Table 1.
Table 1. Grouting Methodology Specifications
Particulars Dimension Unit
Grouting hole diameter 51 mm
Maximum grouting hole drilling considered 6-10 meter
Depth of Grouting below foundation 3 – 6 meter
Hole inclination from vertical 30 – 60 degree
Grouting hole spacing in a line 800 - 1000 mm
Grouting line distance from foundation 1500-2000 mm
Total Pile length 9 meter
Pile hole diameter 125 mm
Pile hole spacing in a line (centre to centre) 250 mm
Pile line distance from foundation 500 mm

In another preferred embodiment of the present invention, grouting chemical is disclosed as a pre-polymer based high strength and free-flowing grouting product comprising of resin and methylene diphenelisocynate. It is a low viscosity, free flowing grouting material with high early strength which is suitable for repairing concrete blocks, asphalt, renderings, stone, asbestos, cement, wood, concrete, and mortar. Its high penetration allows filling the finest of cracks. Further, the varied pressure for injecting predefined grouting chemical in curtain grouting in step A), structural grouting in step B) and reinforcing of soil in step C) is not more than 15 bar.
The chemical specification for carrying out chemical grouting is given below in Table 2. While the end product formed with various combination of chemicals used in grouting are given below in Table 3. The end product formed using a combination of chemicals is water insoluble, fire and water resistant and strengthens the foundation.
Table 2. Chemical Specifications for Grouting
Chemical components Properties
Density(gm/cc) Viscosity (cPs) Epoxy value (eg/kg) Initial Mix Viscosity (cPs/degrees)
Comp-A 0.97-0.99 5 to 20 - 0.5/25
Comp-B 1.13-1.16 1300 to 1800 4.1 to 4.5
Comp-C 1.04 222 -
Comp-D 1.23 230 -
Comp-E
Reference standard ASTM D 1544 ASTM D792-00 ASTM D 1652

Table 3. End product with various combination of chemical components

Chemical components Strength (Mpa) Specific Gravity Inertness
Comp A+B water insoluble, fire and water resistant
Comp C+D 1.09 water insoluble, fire and water resistant
Comp E+F water insoluble, fire and water resistant

EXAMPLE 1
Calculation of chemical quantity per hole

For curtain grouting holes (11) that are 9 meters deep and are being drilled between two micropiles. The influence zone of chemical grouting with additives chemical in the particular soil mass is considered as 250 mm around the periphery of the drill hole. Accordingly the volume of the soil mass is estimated. The requirement of the grouting chemical with additives is of the order of 25-30% by weight of the soil mass to achieve the desired impermeable curtain. The per hole chemical requirement has been calculated for curtain grouting is between 900-950 Kgs/hole. The total chemical requirement for curtain grouting is approximately 90 to 100 tons.
The influence zone of the preferred chemical in the particular soil mass is considered as 0.5 m around the periphery of the drill hole. Accordingly, the volume of the soil mass is estimated. Various laboratory tests has been conducted on the chemical and it is being concluded that the requirement of the preferred chemical is of the order of 30% by weight of the soil mass to achieve the desired consolidation results. Accordingly, per hole chemical requirement has been calculated for consolidation treatment.

EXAMPLE 2
Time required for grouting in 1 hole

The time requirement for grouting per section of 51 mm diameter hole using the preferred chemical shall be 15 to 20 minutes. Considering, grouting in stages starting from bottom to the top of the holes with a waiting time of 20 mins for each section for setting up the chemical. It is estimated that it takes approximately 100 to 120 minutes for complete grouting of 1 hole. While some grouting processes takes hours for the grouting material to set up, the proposed chemical grouting process is saves time.
Therefore, the technological development in the method of soil consolidation using grouting chemical employed in an effective chemical grouting technique for strengthening the load bearing capacity of the soil effectively prevents any risk of underground water connections of the water table with the water bodies, damage to the foundation. Herein, the chemicals used in grouting employed takes less time to set up and consequently reduces time taken for consolidation.
Many modifications and other embodiments of the invention set forth herein will readily occur to one skilled in the art to which the invention pertain having the benefit of the teachings presented in the foregoing descriptions and the associated drawings. Therefore, it is to be understood that the invention is not to be limited to the specific embodiments disclosed and that modifications and other embodiments are intended to be included within the scope of the appended claims. Although specific terms are employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation.

We claim:
1. A method of soil consolidation for an existing building foundation located nearby water bodies comprising steps of:

A) curtain grouting along an outer area (13) of a foundation wall (12);
B) structural grouting for consolidating soil of the building foundation; and
C) reinforcing soil with grout carrying medium (15) below the foundation;

characterized in that,

curtain grouting of step A) comprises the steps of:

a) cementing said foundation wall (12) to prevent any penetration of water;
b) settling plurality of micro-piles (10) at a distance from said foundation wall (12);
c) drilling a plurality of vertical holes (11) at 0.1 meter to 3 meter distance from said foundation wall (12) using steel/PVC casings;
d) inserting plurality of grout carrying medium in holes (11) drilled in step b) and uplifting said steel/PVC casing upto 5 meter height from ground level (19) from holes (11) drilled in step b);
e) placing a reusable inflatable packer (18) at 0.5 meter to 5 meter distance below ground level (19) inside said grout carrying medium inserted in step c);
f) injecting a predefined grouting chemical with varied pressure for pumping of said grouting chemical inside said pipe using grout pumps (17) after packer (18) is placed in step d);
g) stopping chemical injection of step f) when specified chemical quantity for hole (11) drilled in step a) is reached; and
h) removing packer after chemical injection stopped in step f) and sealing the hole (11) drilled in step a);
structural grouting of step B) comprises the steps of:

a) drilling a plurality of 15 degree to 150 degree inclined boreholes (16) at 1 meter to 10 meter distance from foundation wall (12) at predefined angles for grouting from outside (13) & inside (14) of the building using standard drilling machines;
b) grouting in stages in said borehole (16) drilled at step a) starting from bottom of said borehole (16) using grout carrying medium and placing inflatable packers (18) at suitable intervals;
c) injecting a predefined grouting material in said borehole (16) after inflatable packers (18) are placed in step b) with varied pressure; and
d) grouting at ground level (19) for completing the chemical injection in step c) in said borehole (16).
reinforcing soil in step C) comprises the steps of:

a) installing plurality of grout carrying medium (15) at predefined inclined angle from outside (13) and inside (14) of the building in the intermediate points of the boreholes (16) of structural grouting in step B) at defined intervals upto central axis of the foundation wall (12); and
b) injecting a predefined grouting chemical along with said sacrificial anchor bars (15) installed in step a) until a varied pressure is achieved.

2. The method as claimed in claim 1, wherein curtain grouting in step A) is done with preferably resin based chemical.

3. The method as claimed in claim 1, wherein plurality of grout carrying medium used in curtain grouting in step A) are PVC pipes with perforations and covered by rubber tubes to prevent soil or any other material to pass through the perforation.

4. The method as claimed in claim 1, wherein the predefined grouting chemical used in curtain grouting in step A), structural grouting in step B) and reinforcing of soil in step C) is a pre-polymer based high strength and free flowing grouting product comprising of: resin and methylene diphenelisocynate.

5. The method as claimed in claim 1, wherein the varied pressure for injecting predefined grouting chemical in curtain grouting in step A), structural grouting in step B) and reinforcing of soil in step C) is not more than 15 bar.

6. The method as claimed in claim 1, wherein the specified chemical quantity is the maximum grout quantity that depends on dimensions of the hole (11) drilled for curtain grouting in step A).

7. The method as claimed in claim 1, wherein predefined angles for structural grouting in step B) and reinforcing of soil in step C) from outside (13) and inside (14) are ranging from 50-55 ° and 25-35 ° respectively.