Abstract: Sub grade soil strength is an essential input for design of pavements and overlays. Many models are available for determination of subgrade soil strength. Subgrade soil strength in terms of elastic modulus value is used in Mechanistic-Empirical methods and CBR value is used in empirical methods of design. Both the parameters can be used for structural evaluation of flexible pavement. Determination of elastic moduli values of pavement layers by back-calculation of deflections measured using Falling Weight Deflectometer (FWD) is a widely used scientific method. However, extensive use of FWD for large scale evaluation of in-service pavements is not feasible, especially for low volume roads, unimportant roads and roads in developing and under developed countries. In the present investigation, an attempt has been made to develop relationships that can be used to estimate subgrade soil strength in terms of elastic modulus and CBR values using in-situ test results of Dynamic Cone Penetrometer (DCP). As DCP is a portable and low-cost equipment used for quick evaluation of unbound granular and subgrade soil. Comparative studies are also carried out with similar models available from the literature review.

Keywords: Falling weight Deflectometer (FWD), Back-calculated subgrade modulus, California Bearing Ratio (CBR), Dynamic Cone Penetrometer (DCP) and Regression Models.