Prediction of Subgrade Strength Parameters from Dynamic Cone Penetrometer Index, Modified Liquid Limit and Moisture Content

Subgrade soil is an essential component for design of both flexible and rigid pavement structures. Laboratory investigation of subgrade strength parameter as California Bearing Ratio beneficial for design of flexible pavement, Coefficient of subgrade reaction K-Value required for design of rigid pavement, raft footing and unconfined compressive strength (UCS) is useful for determination of shear strength parameter of subgrade. These tests are time consuming and demand significant effort but mandatory. This study considers the use of multiple variable regression analysis (MLR) to predict the California Bearing Ratio (CBR), Coefficient of subgrade reaction K-Value, unconfined compressive strength (UCS), Field dry density from Dynamic Cone Penetrometer (DCP), modified liquid limit and moisture content of subgrade. This paper presents the empirical correlations developed from multiple variable regression analysis from test results obtained from experimental investigation of soil sample taken from different locations of Gujarat region in India. The formulations are validated using other sets of tests data. The developed empirical correlations may be useful in quick determination of strength parameters of subgrade from physical properties of subgrade and Dynamic Cone penetrometer. Results obtained from validation of these developed empirical correlation proves their reliably and accuracy to perform subgrade strength evaluation for both rigid and flexible pavement.