Description:DESCRIPTION:
Field of the invention:
[0001] The present disclosure generally relates to the technical field of soil liquefaction in seismic sites, and in specific relates to a method for detecting the resistance of soil and liquefaction potential index of soil based on a standard penetration test.
Background of the invention:
[0002] The Standard Penetration Test (SPT) is widely used to determine a dynamic in-situ test for providing information about the properties of soil. The standard penetration test has been performed worldwide. The test was introduced by the Raymond concrete pile company in 1902 and remains today as the most common in-situ test worldwide. The procedure for the SPT is detailed in American Society for Tools and Materials (ASTM) D 1586. The penetration test is developed for foundation design purposes. The SPT is the field of the sub-surface sounding with the standards of (IS: 2131-1981).

[0003] The standard penetration test gives a useful guide in ground conditions where more advanced laboratory testing is not practical or possible. The SPT can also be used for the empirical determination of a sand layer's susceptibility to soil liquefaction based on research performed by harry seed and others. When used for this purpose, the N-value should be normalized to a standard overburden stress level. A variety of techniques have been proposed to compensate for the deficiencies of the standard penetration test, including a cone penetration test, in-situ vane shear tests and shear wave velocity measurements.

[0004] The various factors contribute to the variation of the standard penetration number ‘N’ at a given depth for similar soil properties. The SPT is driven into the soil through a bore hole with the desired diameter and depth as done by a hammer weighing 63.5 kg. A drop test is conducted in the borehole with a maximum number of blow counts of the hammer as regards the penetration resistance. The use of the SPT correction factor for corrections for field (energy correction) procedures is always appropriate.

[0005] In earlier days, penetration resistance testing and sampling with an open ended pipe were started in the 1900s. The Raymond concrete pile company developed the standard penetration test with the split barrel sampler in 1927. Since the SPT has been performed worldwide to determine the soil properties. The SPT or variations of the test are the primary means of collecting geotechnical design data in different countries. Penetration tests are used to determine foundation strength and evaluate the liquefaction potential of soil. The significant aspects of the tests and the potential problems that can occur are included.

[0006] In existing technology, a saturated sandy soil liquefaction detection method based on a standard penetration test, which comprises the following steps are establishing the saturated sandy soil liquefaction detection model related to the buried depth of saturated sandy soil, the depth of underground water level, the content of fine particles, the seismic level and the seismic peak acceleration to obtain a critical target penetration number and judging the liquefaction of the saturated sandy soil by using the critical standard penetration number and the corrected actual measurement standard penetration number.

[0007] The defects of the liquefaction formula is danger in a shallow layer and conservative in a deep layer of saturated sand in an earthquake-resistant building design specification (GB 50011-2010) are overcome and the detection result is more accurate. The soil liquefaction judgment of various burial depths and fine particle content can be met under various intensities and the method has wide applicability. However, the saturated sandy soil liquefaction detection method is not apply the field procedure factors to the SPT N values for non-standard SPT procedures based on IS 1893 to influence the study on liquefaction evaluation. The saturated sandy soil liquefaction detection method is not calculated the factor of safety from an uncorrected SPT-N value is overestimated leading to destructive effects during the occurrence of liquefaction.

[0008] Therefore, there is a need for a method that provides a field procedure correction factors are applied for measured SPT N values. There is a need for methods that provide correction factors are applied for non-standard procedures and equipment. There is a need for a method that provides a liquefaction analysis based on field procedure corrected SPT N values that transform most of the subsoil layers at the study from non-liquefiable to liquefiable. There is a need for methods that provide a significant impact on the liquefaction analysis of subsoil strata.
Objectives of the invention:
[0009] The primary objective of the invention is to provide a method for liquefaction analysis based on field procedure corrected SPT N values that transforms most of the subsoil layers at the study from non-liquefiable to liquefiable.

[0010] Another objective of the invention is to provide a method that has a significant impact on the liquefaction analysis of subsoil strata.

[0011] The other objective of the invention is to provide a method is standard penetration test is conducted on any type of soil structure.

[0012] The other objective of the invention is to provide a method to determine the relative density and angle of shearing resistance of cohesion less soils and also the strength of stiff cohesive soils.

[0013] Yet another objective of the invention is to provide a method for detecting a liquefaction potential index of the soil in the field in real time result.

[0014] Further objective of the invention is to provide a method that is relatively simple and inexpensive to perform for detecting the liquefaction potential index of the soil.
Summary of the invention:
[0015] The present disclosure proposes a method for field procedure corrections of SPT N-values on the liquefaction potential of soils. The following presents a simplified summary in order to provide a basic understanding of some aspects of the claimed subject matter. This summary is not an extensive overview. It is not intended to identify key/critical elements or to delineate the scope of the claimed subject matter. Its sole purpose is to present some concepts in a simplified form as a prelude to the more detailed description that is presented later.

[0016] In order to overcome the above deficiencies of the prior art, the present disclosure is to solve the technical problem to provide a method for detecting the resistance of soil and the potential index of soil based on a standard penetration test.

[0017] According to an aspect, the invention provides a SPT method for detecting a liquefaction potential index of soil. First, at one step, conducting the SPT manually using standard SPT equipment and a procedure for measuring a SPT N-value for liquefaction evaluation of subsoil. At another step, applying field procedure correction factors for non-standard SPT procedures and equipment individually to influence studies on liquefaction evaluation. At another step, obtaining a corrected SPT N-value of the subsoil upon applying the field procedure correction factors to measured SPT N-values of the subsoil.

[0018] Further, at another step, calculating a factor of safety (FOS) as the ratio of Cyclic Resistance Ratio (CRR) to Cyclic Stress Ratio (CSR). The corrected SPT N-value of the subsoil has a significant impact on liquefaction analysis of subsoil strata at study areas and implications of application and non-application of the field procedure corrections to the SPT N-value of the subsoil strata on liquefaction potential index and associated severity.

[0019] In one embodiment herein, the liquefaction potential of soil based on SPT test data is calculated as the factor of safety (FOS) from the uncorrected SPT N-value to reduce devastating effects during the occurrence of liquefaction and correction factors for field procedures are applied to reduce the 30–40% of standard SPT – N measure values.

[0020] In one embodiment herein, the SPT N-values for non-standard SPT procedures are evaluated by the idriss and boulanger method to influence liquefaction evaluation. The field procedure corrections are required to the SPT N–value for an exact assessment of the liquefaction of different soils. In one embodiment herein, the SPT N–values are efficiency varying by selecting the standard SPT equipment include a donut hammer, a safety hammer, a drop hammer and an automatic hammer. The SPT N–values detect the liquefaction of subsoil and estimate soil parameters to bear the capacity of the structure or foundation.

[0021] Further, objects and advantages of the present invention will be apparent from a study of the following portion of the specification, the claims, and the attached drawings.
Detailed description of drawings:
[0022] The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate an embodiment of the invention, and, together with the description, explain the principles of the invention.

[0023] FIG. 1 illustrates a flowchart of a method for field procedure corrections of SPT N-values on the liquefaction potential of soils, in accordance to an example embodiment of the invention.
Detailed invention disclosure:
[0024] Various embodiments of the present invention will be described in reference to the accompanying drawings. Wherever possible, same or similar reference numerals are used in the drawings and the description to refer to the same or like parts or steps.

[0025] The present disclosure has been made with a view towards solving the problem with the prior art described above, and it is an object of the present invention to provide a method for detecting the resistance of soil and potential index of soil based on a standard penetration test.

[0026] According to an exemplary embodiment of the invention, FIG. 1 refers to a flowchart 100 of a method for field procedure corrections of SPT N-values on the liquefaction potential of soils. First, one step 102, conducting the SPT manually using standard SPT equipment and a procedure for measuring a SPT N-value for liquefaction evaluation of subsoil. At step 104, applying field procedure correction factors for non-standard SPT procedures and equipment individually to influence studies on liquefaction evaluation.

[0027] At step 106, obtaining a corrected SPT N-value of the subsoil upon applying the field procedure correction factors to measured SPT N-values of the subsoil. Further, at step 108, calculating a factor of safety (FOS) as the ratio of Cyclic Resistance Ratio (CRR) to Cyclic Stress Ratio (CSR).

[0028] According to an exemplary embodiment of the invention, herein the standard penetration test is conducted by means of a split spoon as specified standard, furnishes data about the resistance of the soil to penetration that can be used to evaluate standard strength data such as N values (number of blows per 30 cm of penetration using the split spoon) of the soil.

[0029] In one embodiment herein, the first 15 cm of drive a borehole as considering the seating drive. The total blows required for the second and third 25 cm of penetration shall be termed the penetration resistance N value, if the split spoon sampler is driven less than 45cm into the total penetration hole. The correction factor includes the height of the hammer falling, non-standard hammer weight, standard sampler and non-standard borehole diameter.

[0030] Because the subsoil liquefaction is varies in some conditions of magnitude of an earth quake and seismic areas is termed as the factor of safety (FOS) defines the ratio of cyclic resistance (CRR) to cyclic stress ratio (CRR) to reduce devastating effects during the occurrence of liquefaction. The correction factor for soil liquefaction is applied to reduce the 30–40% standard of SPT–N measure values. The non-standard SPT procedure is evaluated by the Idriss and Boulanger method to determine its influence on liquefaction evaluation.

[0031] According to an exemplary embodiment of the invention, herein the standard penetration test (SPT) is purposes to conduct for identify the type and nature of the soil at various depths and to determine the penetration resistance of the soil. The equipment required to perform the SPT test is drilling equipment, a split spoon sampler, a dropping hammer, a driving head (anvil) and a guiding rod. The STP test procedure on the site is firstly, dig the starting borehole with boring equipment. Before conducting the test decide the depth of penetration bore and depth interval to carry out the test and collect the sample. Take the borehole depth up to 10 m as generally, the depth of the bore is up to the ground water table or up to hard strata below the ground surface. So, SPT is conducted every one meter of boring below ground level and soil samples are collected at the same depth.

[0032] Table 1:
SL. No Element Standard Specification
1. Sampler Standard split-spoon sampler with, outside diameter, OD=51mm; and inside diameter, ID=35mm (constant, that is, no room for liners in the barrel)
2. Drill rods A or AW type for depths less than 15.2m; Nor NW type for greater depths
3. Hammer Standard (safety) hammer with, A ) weight=63.5kg;and b) drop height =762 mm (deliver 60 percent of theoretical free fall energy )
4. Rope Two wraps of rope around the pulley
5. Borehole 100-130 mm diameter rotary bore hole with bentonite mud for borehole stability (hollow stem augers where SPT is taken through the stem)
6. Drill bit Upward deflection of drilling mud (baffled drag bit)
7. Blow count rate 30 to 40 blows per minute

8. penetration Measured over range of 150mm–450mm of penetration into the ground resistant count

[0033] Table. 1 depicts the standardized SPT equipment (IS 1893-2016 part- 1).

[0034] Next, assemble the sampler, Once the boring of the hole is done up to the desired depth (1 m depth we decided), remove the drilling tools from the borehole and clean up all the disturbing materials. After that, fit the soil sampler named the split spoon sampler with the drilling rod and lower it into the borehole. The rest of the split spoon sampler was attracted by a drilling rod at the bottom of the drilled borehole of undistributed soil.

[0035] Next, assemble the equipment, place the sampler rest on the bottom of the borehole conduct the SPT test. Assembly of the test equipment of hammer, anvil and guiding rod. Next, conduct the SPT test, by driving the drop hammer on the bottom of a borehole with blows from the slide hammer with a mass of 63.5kg falling through a distance of 750 mm or 30 inches, at a rate of 30 blows per minute.

[0036] Table 2:
SL No. Correction Correction Factor
1. Non-standard hammer weight or height of fall CHT = 0.75 (for Donut hammer with rope and pulley)
= 1.33(for Donut hammer with trip/auto) and Energy ratio=80 percent
2. Non-standard hammer weight or height of fall CHW =HW/48387 where H = height of fall (mm), and W = hammer weight (kg)
3. Non-standard sampler setup (standard samples with room for liners, but used without liners) CSS = 1.1 (for loose sand)
= 1.2 (for dense sand)
4. Non-standard sampler setup (standard samples with room for liners, but liners are used) CSS = 0.9 (for loose sand)
= 0.8 (for dense sand)
5. Short rod length CRL = 0.75 (for rod length 0-3 m)
= 0.80 (for rod length 3-4 m)
= 0.85 (for rod length 4-6 m)
= 0.95 (for rod length 6-10 m)
= 1.0 (for rod length 10-30 m)
6. Non-standard bore hole diameter CBD = 1.00 (for bore hole diameter of 65-115 mm)
= 1.05 (for bore hole diameter of 150 mm)
= 1.15 (for bore hole diameter of 200 mm)

[0037] Table. 2 depicts the correction factor for non-standard procedures and equipment (IS: 1893-2016 part- 1)

[0038] Count the number of blows required to reach the depth of 150mm. Again, drive the sampler into the soil and count the blows needed to penetrate the second and third 150 mm. In this test, the total sum of the number of blows required to drive the sampler to 150mm (6 in.) of penetration is the N-value. If the sampler is driven less than 450 mm, then the N-value shall be for the penetration. If the number of blows required to drive the sampler to a depth of 150 mm in excess of the value of 50, it is considered a refusal, and the test is discontinued. The entire sampler may sink sometimes under its own weight, very soft subsoil strata have been discontinued. In some situations, it may be necessary to give any blow to the sampler and N-value is indicated as zero. The test may be made at shorter intervals if necessary or specified.

[0039] Collect the soil sample from the borehole, take out the spilled sampler carefully and separate the sampler from the drilling rod and remove any excess soil from the bottom. Slowly open one side of the split spoon sampler to expose fresh material and any stratification. Record the length, composition, color, stratification and condition of the sample. Remove the soil specimen from the split spoon sampler and pack it in a plastic bag. Further tests are needed to determine the soil's properties.

[0040] Numerous advantages of the present disclosure may be apparent from the discussion above. In accordance with the present disclosure, the SPT method is used to detect the potential index of subsoil. The proposed method of liquefaction analysis based on field procedure corrected SPT N-values transformed most of the subsoil layers at the study from non-liquefiable to liquefiable. The proposed method has a significant impact on the liquefaction analysis of subsoil strata. The proposed method is relatively simple and inexpensive to perform.

[0041] It will readily be apparent that numerous modifications and alterations can be made to the processes described in the foregoing examples without departing from the principles underlying the invention, and all such modifications and alterations are intended to be embraced by this application.
, Claims:CLAIMS:
I / We Claim:
1. A method for field procedure corrections of SPT N-values on the liquefaction potential of soils, comprises:
conducting the SPT manually using standard SPT equipment and a procedure for measuring a SPT N-value for liquefaction evaluation of subsoil;
applying field procedure correction factors for non-standard SPT procedures and equipment individually to influence studies on liquefaction evaluation;
obtaining a corrected SPT N-value of the subsoil upon applying the field procedure correction factors to measured SPT N-values of the subsoil; and
calculating a factor of safety (FOS) as the ratio of Cyclic Resistance Ratio (CRR) to Cyclic Stress Ratio (CSR),
whereby the corrected SPT N-value of the subsoil has a significant impact on liquefaction analysis of subsoil strata at study areas and implications of application and non-application of the field procedure corrections to the SPT N-value of the subsoil strata on liquefaction potential index and associated severity.
2. The method for detecting the liquefaction potential index as claimed in claim 1, wherein the SPT N-values for non-standard SPT procedures are evaluated by an Idriss and Boulanger method to influence liquefaction evaluation.
3. The method for detecting the liquefaction potential index as claimed in claim 1, wherein the field procedure corrections are required to the SPT N–value for an exact assessment of the liquefaction of different soils.
4. The method for detecting the liquefaction potential index as claimed in claim 1, wherein the SPT N–values are efficiency varying by selecting the standard SPT equipment include a donut hammer, a safety hammer, a drop hammer and an automatic hammer.
5. The method for detecting the liquefaction potential index as claimed in claim 1, wherein the SPT N–values detect the liquefaction of subsoil and estimate soil parameters to bear the capacity of the structure or foundation.