Description:DESCRIPTION:
Field of the invention:
[0001] The present disclosure generally relates to the technical field of geo-technical engineering and pavement design, in specific, relates to a method for determining California Bearing Ratio (CBR) of low-compressible clays from Dynamic Cone Penetration Index (DCPI) measured in the field, thereby providing a rapid and economical alternative to traditional, time-consuming laboratory CBR test for pavement design applications.
Background of the invention:
[0002] Flexible pavements have been the predominant type of road used in Saudi Arabia and other parts of the world, with most paved surfaces falling under this category. They can be classified as either conventional or full-depth pavements. Conventional flexible pavements are layered systems comprising an asphalt mixture (wearing course) over one or more granular layers (base and sub-base), all constructed over sub-grade soil. The granular base and sub-base layers are crucial components that reduce traffic-induced stresses and minimize rutting in the base, sub-base, and sub-grade.

[0003] All pavement systems are built on earth, with nearly all components made from earth materials. A typical flexible pavement consists of a bituminous composite wearing course built over a base course and sub-base, which rest on a compacted subgrade. The base may be stabilized with asphalt, cement, lime, or other stabilizers, or left untreated, using granular material with specific physical properties.

[0004] In general, concrete refers to any material made of a mixture of aggregates, such as sand, gravel, or crushed stone, bound together by cement. Asphalt concrete is composed of asphalt cement and aggregate. Base courses typically consist of aggregates like gravel and crushed rock, which may be compacted or stabilized with lime, Portland cement, or asphalt. Sub-bases usually use local aggregate materials and can be either compacted aggregate or stabilized materials. The subgrade is the top surface of a roadbed on which the pavement structure and shoulders are built. Its purpose is to provide a platform for pavement construction and to support the pavement without excessive deflection that would affect its performance. The upper layer of this natural soil may be compacted or stabilized to increase its strength.

[0005] Traditionally, the California Bearing Ratio (CBR) test is a widely recognized method for evaluating the subgrade strength of soil and base materials used in road construction. Developed by the California Division of Highways in the 19th century, the CBR test measures the resistance of a soil sample to penetration by a standardized piston under controlled moisture and density conditions. The test is performed by compacting soil in a mold, saturating it (in soaked conditions), and then applying a load to measure the pressure required to achieve a specified penetration depth.

[0006] Despite its widespread use and acceptance, the CBR test has several limitations. It is labour-intensive, time-consuming, and requires specialized laboratory equipment and conditions, making it less suitable for rapid on-site evaluations. Furthermore, the results can vary significantly depending on the soil type, moisture content, and compaction level, necessitating careful sample preparation and testing procedures.

[0007] In existing technology, a method for predicting the California bearing ratio of subgrade material, includes collecting sample from various regions within the subgrade, which are then tested to determine the moisture content and density. Each sample is prepared at optimal moisture content and various densities, succeeded by testing to ascertain the CBR for each density, thereby generating a dataset of variables. Selected variables from this dataset are subjected to a multiple linear regression model, establishing a relationship between the determined CBR value and these variables. However, the method might not provide accurate results.

[0008] Therefore, there is a need for a method for determining California Bearing Ratio (CBR) of low-compressible clays from Dynamic Cone Penetration Index (DCPI) measured in the field, thereby providing a rapid and economical alternative to traditional, time-consuming laboratory CBR test for pavement design applications. There is also a need for a method that reduces time-consuming and expensive laboratory CBR tests with the quicker and more economical DCPT, which takes about 15 minutes to execute.

[0009] There is also a need for a method that leads to faster decision making and project execution in pavement design for low compressible clay subgrades. Further, there is also a need for a method that develops correlation for low compressible clay, thereby enhancing the method reliability for pavement construction.
Objectives of the invention:
[0010] The primary objective of the present invention is to provide a method for determining California Bearing Ratio (CBR) of low-compressible clays from Dynamic Cone Penetration Index (DCPI) measured in the field, thereby providing a rapid and economical alternative to traditional, time-consuming laboratory CBR test for pavement design applications.

[0011] Another objective of the present invention is to provide a method that reduces time-consuming and expensive laboratory CBR tests with the quicker and more economical DCPT, which takes at least 15 min to execute.

[0012] The other objective of the present invention is to provide a method that reduces the time and cost associated with pavement design for projects involving low compressible clays.

[0013] The other objective of the present invention is to provide a method that leads to faster decision making and project execution in pavement design for low compressible clay subgrades.

[0014] The other objective of the present invention is to provide a method that conducts DCP tests in both pre-monsoon and monsoon seasons, thereby allowing for a more accurate assessment of subgrade strength under different environmental conditions.

[0015] The other objective of the present invention is to provide a method that develops correlation for low compressible clay, thereby enhancing the method reliability for pavement construction.

[0016] Yet another objective of the present invention is to provide a method that collects soil samples from various depths and re-moulding them in the laboratory to match field density and moisture content.

[0017] Further objective of the present invention is to measure various soil properties such as grain size distribution, atterberg limits, field moisture content, field density, specific gravity, free swell index, and hydrometer analysis.
Summary of the invention:
[0018] The present disclosure proposes a method for determining california bearing ratio of low compressible clay. 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.

[0019] 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 determining California Bearing Ratio (CBR) of low-compressible clays from Dynamic Cone Penetration Index (DCPI) measured in the field, thereby providing a rapid and economical alternative to traditional, time-consuming laboratory CBR test for pavement design applications.

[0020] According to one aspect, the invention provides a method for determining california bearing ratio (CBR) for low compressibility clay. At one step, the dynamic cone penetration test (DCPT) conducts at selected locations at varying depths of up to 1 meter below a ground surface and soil samples are collected at each depth for laboratory investigations. At another step, the collected soil samples are prepared in a laboratory by compacting them to field density and field moisture content to conduct CBR tests.

[0021] At another step, the standard laboratory california bearing ratio (CBR) test performs on the prepared soil samples in both un-soaked and soaked conditions to obtain corresponding CBR values. At another step, the soil properties including grain size distribution, atterberg limits, field moisture content, field density, specific gravity, free swell index, and hydrometer analysis are measured. At another step, establishes the correlation between dynamic cone penetration index (DCPI) measurements obtained from the field tests and the CBR values obtained from the laboratory tests using regression analysis models.

[0022] At another step, validated the correlation using Indian Roads Congress (IRC)-37 by determining deviation between actual CBR values obtained from laboratory and predicted CBR values obtained from the developed correlation for low compressible clays in both un-soaked and soaked conditions. Further, at another step, the determined CBR values applies for the evaluation of subgrade soil strength in pavement construction.

[0023] In one embodiment, the DCPT are conducted in both pre-monsoon and monsoon periods to account for seasonal variations in soil moisture content. In one embodiment the soil samples are collected from depths specifically at the ground surface, 0.5 meters below ground level, and 1 meter below ground level.

[0024] In one embodiment, the correlation between the DCPI measurements and CBR values is developed with a coefficient of determination (R2) of 0.86, thereby ensuring high reliability and accuracy in the prediction of the CBR values for low compressible clays. In one embodiment, the regression analysis models are configured to incorporate data from pre-monsoon and monsoon periods separately and combined together, thereby establishing a robust relationship suitable for predicting the CBR values in both un-soaked and soaked conditions.

[0025] In one embodiment, the established correlation between the DCPI measurements and CBR values for low compressibility clay (CL) soils with a free swell index (FSI) of less than or equal to 35 percent. In one embodiment, the determined CBR values from the DCPI measurements are used in the pavement construction to evaluate the subgrade soil strength adequate for low compressible clays. In one embodiment, the laboratory CBR test is configured to compact the soil samples to achieve a density equal to the field density determined for the corresponding sample depth.

[0026] 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:
[0027] 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.

[0028] FIG. 1 illustrates a flowchart of a method for determining California bearing ratio (CBR) for low compressibility clay, in accordance to an exemplary embodiment of the invention.

[0029] FIG. 2 illustrates a flowchart of a method for determining California bearing ratio (CBR) from dynamic cone penetration test (DCPT) for low compressible clay, in accordance to an exemplary embodiment of the invention.

[0030] FIG. 3A illustrates a graphical representation of a dynamic cone penetration index DCPI with the CBR plot of low compressibility clay (CL) soil for pre-monsoon period data, in accordance to an exemplary embodiment of the invention.

[0031] FIG. 3B illustrates a graphical representation of the DCPI with the CBR plot of low compressibility clay (CL) soil for monsoon period data, in accordance to an exemplary embodiment of the invention.

[0032] FIG. 3C illustrates a graphical representation of the DCPI with the CBR plot of low compressibility clay (CL) soil for pre-monsoon and monsoon periods data, in accordance to an exemplary embodiment of the invention.
Detailed invention disclosure:
[0033] 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.

[0034] 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 determining California Bearing Ratio (CBR) of low-compressible clays from Dynamic Cone Penetration Index (DCPI) measured in the field, thereby providing a rapid and economical alternative to traditional, time-consuming laboratory CBR test for pavement design applications.

[0035] According to one exemplary embodiment of the invention, FIG. 1 refers to a flowchart 100 of a method for determining the California bearing ratio (CBR) for low compressibility clay. At step 102, the dynamic cone penetration test (DCPT) is conducted at selected location at varying depths of up to 1 meter below the ground surface and soil samples are collected at each depth for laboratory investigations. At step 104, the collected soil samples are prepared in a laboratory by compacting them to field density and field moisture content to conduct CBR tests.

[0036] At step 106, the standard laboratory California bearing ratio (CBR) test is performed on the prepared soil samples in both un-soaked and soaked conditions to obtain corresponding CBR values. At step 108, the measures the soil properties including grain size distribution, atterberg limits, field moisture content, field density, specific gravity, free swell index, and hydrometer analysis. At step 110, establish the correlation between the dynamic cone penetration index (DCPI) measurements obtained from the field tests and the CBR values obtained from the laboratory tests using regression analysis models.

[0037] At step 112, validated the correlation using Indian Roads Congress (IRC)-37 by determining the deviation between actual CBR values obtained from laboratory and predicted CBR values obtained from developed correlation for low-compressible clays in both un-soaked and soaked conditions. Further, at step 114, the determined CBR values apply for the evaluation of subgrade soil strength in pavement construction.

[0038] In one embodiment, the DCPT is conducted in both pre-monsoon and monsoon periods to account for seasonal variations in soil moisture content. In one embodiment, the soil samples are collected from depths specifically at the ground surface, 0.5 meters below ground level, and 1 meter below ground level.

[0039] In one embodiment, the correlation between the DCPI measurements and CBR values is developed with a coefficient of determination (R2) of 0.86, indicating that 85 to 87 percent of the variability in the CBR values is represented by the DCPI measurements, thereby ensuring high reliability and accuracy in the prediction of the CBR values for low-compressible clays. In one embodiment, the regression analysis models are configured to incorporate data from pre-monsoon and monsoon periods separately and combined together, thereby establishing a robust relationship suitable for predicting the CBR values in both un-soaked and soaked conditions.

[0040] In one embodiment, the established correlation between the DCPI measurements and CBR values for low compressibility clay (CL) soils with a free swell index (FSI) of less than or equal to 35 percent. In one embodiment, the determined CBR values from the DCPI measurements are used in the pavement construction to evaluate whether the subgrade soil strength is adequate for low compressible clays. In one embodiment, the laboratory CBR test is configured to compact the soil samples to achieve a density equal to the field density determined at corresponding sample depth.

[0041] According to another exemplary embodiment of the invention, FIG. 2 refers to a flowchart 200 of a method for determining the California bearing ratio (CBR) from the dynamic cone penetration test (DCPT) for low compressible clay. In one embodiment, the dynamic cone penetrometer includes a handle, a hammer, an upper rod, an anvil, a pin, an upper attachment, a drive rod, a scale, a foot, and a disposable cone. The handle is located at the top of the penetrometer and allows the user to hold and operate the device.

[0042] In another embodiment, the hammer is positioned beneath the handle. This heavy hammer is dropped from a specific height to drive the disposable cone into the ground. The anvil, which is struck by the hammer, drives the disposable cone into the soil and absorbs the impact force, directing it downward. The drive rod extends from the anvil to the tip of the disposable cone and transmits the hammer's force to the cone. The disposable cone, located at the bottom of the drive rod, penetrates into the soil when struck by the hammer. It has a standardized 60-degree angle and size for consistent results. A scale along the drive rod measures the penetration depth of the cone after each hammer blow.

[0043] In a contemporary examination, the relationship between CBR and DCPI for low compressibility clay is established. Soil samples are collected at varying depths (near ground level, 0.5 meters below ground level, and 1 meter below ground surface) from 21 trial pits in the eastern coastal region of Peninsular India. The dynamic cone penetration test (DCPT) is performed following ASTM D6951/D6951M-09 standards. The DCPT is conducted until the cone penetrates the soil up to 1 meter. DCPI is measured in millimeter per blow.

[0044] In one embodiment herein, the field density is determined using the core cutter method as per Indian Standard (IS) 2720 at the same test locations where the DCP tests are performed. DCP tests are conducted during pre-monsoon and monsoon periods, corresponding to unsoaked and soaked CBR tests, respectively. The CBR tests simulate field conditions in the laboratory by compacting the soil to its natural moisture content and field density. Soil samples from various depths and locations are tested in the laboratory for properties like specific gravity, free swell index, hydrometer, grain size distribution, Atterberg limits, natural moisture content, and CBR as per IS-2720.

[0045] At one step 202, the process begins with selecting appropriate locations that contain low compressible clay. At step 204, the experimental investigation is divided into two main parts, which are field investigations 204 and laboratory investigations 206. At step 208, the dynamic cone penetration test (DCP) is conducted at the desired location. The DCP test is performed in two different seasonal conditions that are pre-monsoon and monsoon (210, 212) to capture the variations in moisture content that occur throughout the year. The tests provide DCPI measurements which are an indicator of the penetration resistance.

[0046] At step 206, the clay samples are collected from each test location at three different depths from ground level, 0.5 meters below ground level, and 1 meter below ground level. The CBR test is performed on the collected clay samples in both un-soaked and soaked conditions to obtain corresponding CBR values. The soil properties 214 including grain size distribution, atterberg limits, field moisture content, field density, specific gravity, free swell index, and hydrometer analysis are measured. These additional properties can help in better understanding of characteristics of the soil samples.

[0047] At step 216, the laboratory CBR tests are performed on the soil samples in two conditions, which are FMC-FDD Condition (Field Moisture Content-Field Density) 218 and Soaked Condition 220. The conditions simulate the real-world scenarios that the soil might experience. The laboratory CBR test is configured to compact the soil samples to achieve a density equal to the field density.

[0048] At step 222, the development of correlation equation between the CBR values and DCPI measurements. The field DCP tests and laboratory CBR tests (including additional soil properties) are conducted, it is analysed to establish correlations between DCPI measurements and CBR values for low-compressible clays. The separate correlations are established for un-soaked and soaked conditions to account for the effect of moisture content on the soil strength.

[0049] The correlation equation for prediction of laboratory CBR values from the DCPI measurements is CBR = 9802.4(DCPI)-2.322 with R2 value of 0.86, indicating that 85 to 87 percent of the variability in the CBR values is represented by the DCPI measurements, thereby ensuring high reliability and accuracy in the prediction of the CBR values for low compressible clays. The developed correlation equation indicated deviation in predicted CBR values within ±1 for CBR values of CL soil (below 5 percent) and is in agreement with the IRC-37 tolerance limit.

[0050] At step 224, the correlation is validated to ensure a high coefficient of determination, and CBR values are determined from DCPI measurements from the regression analysis models for low-compressible clays in both un-soaked and soaked conditions. The accuracy and generalizability of the established correlations are verified using a separate set of clay samples and DCPI measurements collected from different locations not included in the initial data collection process.

[0051] After validation, the established correlation can be used to determine the CBR of low-compressible clays in un-soaked and soaked conditions based on the new DCPI measurements obtained from field tests. This eliminates the need for time-consuming and expensive laboratory CBR tests, allowing for faster and more economical evaluation of subgrade strength in pavement construction involving low-compressible clays.

[0052] According to another exemplary embodiment of the invention, FIG. 3A refers to a graphical representation 302 of the dynamic cone penetration index DCPI with the CBR plot of low compressibility clay (CL) soil for pre-monsoon period data. In one embodiment herein, the x-axis represents the Dynamic Cone Penetration Index (DCPI) in millimeters per blow (mm/blow), and the y-axis represents the California Bearing Ratio (CBR) as a percentage (%). Each blue dot represents a pair of DCPI and CBR values obtained from field and laboratory tests, respectively. The dotted regression line is plotted through the data points to show the correlation between DCPI and CBR.

[0053] The equation of the regression line is given as y = 4407.3x-2.071. The coefficient of determination (R2) value is 0.88, which indicates the strength of the correlation between DCPI and CBR. The high R² value (0.88) validates the accuracy and reliability of the regression model, confirming that the DCPI can be used as a rapid and economical alternative to determine CBR values for low compressibility clays. The established correlation can be utilized for quick evaluation of subgrade soil strength in pavement design and construction, saving time and reducing costs compared to traditional methods.

[0054] In one embodiment herein, the soil properties at the site are obtained through field and laboratory investigations. The soil samples collected from the site at varying depths are classified as low compressible clay (CL). The properties of clay are presented in Table. 1.

[0055] Table. 1

[0056] In one embodiment herein, the Table. 1 depicts the soil properties of different test locations and depths, and includes various parameters that are essential for understanding the soil characteristics. The results of CBR and DCPI obtained from the work, during the pre-monsoon and monsoon periods are represented in Table. 2.

[0057] Table. 2

[0058] According to another exemplary embodiment of the invention, FIG. 3B refers to a graphical representation 304 of the DCPI with the CBR plot of low compressible clay (CL) soil for monsoon period data. In one embodiment herein, the relationship between Dynamic Cone Penetration Index (DCPI) and California Bearing Ratio (CBR) for CL soil (clay with low compressibility) during the monsoon season. The x-axis represents the DCPI (mm/blow), which represents the Dynamic Cone Penetration Index (DCPI) measured in millimeters per blow. Higher DCPI measurements indicate lower soil strength. The y-axis is labelled as CBR (%), which represents the California Bearing Ratio, higher CBR values indicate higher soil strength.

[0059] There are a number of data points plotted on the graph. These data points show a general trend where CBR decreases as DCPI increases, thereby indicating that as the DCPI measurements (penetration depth per blow) increases, signifying weaker soil, the CBR (subgrade strength) of the soil decreases. The dotted line provides a visual representation of the average relationship between DCPI and CBR for the monsoon period CL soil data. The equation for this trend line is likely displayed near the top of the graph as y = 10760x-2.367and the R² value (coefficient of determination) is 0.81. The R² value of 0.81 indicates a reasonably strong positive correlation between DCPI and CBR for the monsoon period CL soil data. The R² value of 1 would indicate a perfect positive correlation, while 0 would indicate no correlation. A value closer to 1 suggests a more reliable prediction of CBR based on DCPI measurements using the established correlation.

[0060] According to another exemplary embodiment of the invention, FIG. 3C refers to a graphical representation 306 of the DCPI with the CBR plot of low compressibility clay (CL) soil for pre-monsoon and monsoon periods data combined together. In one embodiment herein, the x-axis represents the DCPI (mm/blow), the higher DCPI measurements indicate lower soil strength and the y-axis represent the CBR (%), the higher CBR values indicate higher soil strength. The dotted line represents the general downward trend for both pre-monsoon and monsoon data, indicating that as the DCPI increases (weaker soil), the CBR decreases (lower subgrade strength).

[0061] By comparing the pre-monsoon and monsoon data sets, the graph might reveal how the relationship between DCPI and CBR is affected by seasonal moisture variations. Typically, higher moisture content (monsoon) can lead to weaker soil strength, potentially reflected in a lower average CBR for the monsoon data points compared to the pre-monsoon data points.

[0062] Table. 3
Soil Season Correlation equation R² Model
Low compressible clay (CL) Pre monsoon CBR = 4407.3 (DCPI)-2.071 0.88 Power
Monsoon CBR = 10760 (DCPI)-2.367 0.81 Power
Pre-monsoon
and monsoon CBR = 9802.4 (DCPI)-2.322 0.86 Power

[0063] Based on the results, it is clear that the relationship between DCPI measurements and CBR values for both pre-monsoon and monsoon periods combined together follows a power regression model with the R² value of 0.86. Therefore, the combined relationship between CBR and DCPI for both periods is adopted.

[0064] In one embodiment herein, the correlation equation derived from the study is validated using DCPI and CBR test data collected from 12 additional locations (at ground level, 0.5m depth below ground level, and 1m depth below ground level) at the same site during both pre-monsoon and monsoon periods. The deviation between the laboratory-determined CBR values and the predicted CBR values from the correlation equations are calculated and presented in Table 4.

[0065] Table. 4

[0066] In one embodiment herein, the Table. 4 depicts the deviations falling within the range of ±0.3. The CBR values are up to 5%, and the permissible deviation is ±1 within this range. Therefore, the deviations between the predicted CBR values from the correlation equation and the corresponding laboratory CBR values are within the ±1 acceptable range. Thus, the developed correlation equation for low compressibility clay is valid for estimating CBR values from measured DCPI measurements in the field.

[0067] Numerous advantages of the present disclosure may be apparent from the discussion above. In accordance with the present disclosure, a method for determining the California bearing ratio (CBR) for low compressibility clay is disclosed. The proposed method reduces time-consuming and expensive laboratory CBR tests with the quicker and more economical DCPT, which takes only 15 minutes to execute the test. The proposed method reduces the time and cost associated with pavement design for projects involving low compressible clays.

[0068] The proposed method leads to faster decision making and project execution in pavement design for low compressible clay subgrades. The proposed method conducts DCP tests in both pre-monsoon and monsoon seasons, thereby allowing for a more accurate assessment of subgrade strength under different environmental conditions.

[0069] The proposed method develops correlation for low compressible clay, thereby enhancing its reliability for pavement construction. The proposed method collects soil samples from various depths and re-molds them in the laboratory to match field density and moisture content. Various soil properties, such as grain size distribution, atterberg limits, field moisture content, field density, specific gravity, free swell index, and hydrometer analysis are measured.

[0070] 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 determining california bearing ratio (CBR) for low compressibility clay, comprising:
conducting a dynamic cone penetration test (DCPT) at selected locations and collecting soil samples at varying depths of up to 1 meter below a ground surface;
preparing the collected soil samples in a laboratory by compacting them to field density and field moisture content to conduct CBR tests;
performing a standard laboratory california bearing ratio (CBR) test on the prepared soil samples in both un-soaked and soaked conditions to obtain corresponding CBR values;
measuring soil properties including grain size distribution, atterberg limits, field moisture content, field density, specific gravity, free swell index, and hydrometer analysis;
establishing a correlation between dynamic cone penetration index (DCPI) measurements obtained from the field tests and the CBR values obtained from the laboratory tests using regression analysis models;
validating the correlation using Indian Roads Congress (IRC)-37 by determining the deviation between actual CBR values obtained from laboratory and predicted CBR values obtained from the developed correlation for low compressible clays in both un-soaked and soaked conditions; and
applying the determined CBR values for the evaluation of subgrade soil strength in a pavement construction.
2. The method as claimed in claim 1, wherein the soil samples are collected at multiple depths include the ground surface, 0.5 meters below a ground level, and 1 meter below the ground level.
3. The method as claimed in claim 1, wherein the DCPT is conducted in both pre-monsoon and monsoon periods to account for seasonal variations in soil moisture content.
4. The method as claimed in claim 1, wherein the determined CBR values from the DCPI measurements are used in the pavement construction to evaluate the subgrade soil strength that is acceptable for low compressible clays.
5. The method as claimed in claim 1, wherein the correlation between the DCPI measurements and the CBR values is developed with a coefficient of determination (R2) of 0.86, thereby ensuring high reliability and accuracy in the prediction of the CBR values for the low compressible clays.
6. The method as claimed in claim 1, wherein the regression analysis models are configured to incorporate data from pre-monsoon and monsoon periods separately and combined together, thereby establishing a robust relationship suitable for predicting the CBR values in the both un-soaked and soaked conditions.
7. The method as claimed in claim 1, wherein the laboratory CBR test is configured to compact the soil samples to achieve a density equal to the field density determined for the corresponding sample depth.
8. The method as claimed in claim 1, wherein the established correlation between the DCPI measurements and CBR values for low compressibility clay (CL) soils with a free swell index (FSI) of less than or equal to 35 percent.