Resilient Modulus Prediction of Subgrade Soil Using Dynamic Cone Penetrometer

Abstract

Stress-strain response of pavement structure is commonly presented with resilient modulus (Mr). Resilient behavior of subgrade soils is measured using expensive laboratory tests, that is somewhat time-consuming. Design engineers sometimes, uses overestimated backcalculated values from non-destructive test, which in turn lead to over-design of pavement. These challenges encourage the need for a valuable and inexpensive insitu geotechnical testing procedures that can easily and directly determine Mr of subgrade. As most of this testing equipment are not readily available in the University laboratories and highway engineering research centers in Nigeria. Furthermore, it is very difficult to perform Mr testing at desired in-situ condition. Therefore, it becomes imperative to evaluate Mr of subgrade soils using dynamic cone penetrometer (DCP) and California Bearing Ratio (CBR) Test. Such a rational approach is used in this investigation to ascertain resilient performance of an existing pavement foundation (subgrade) situated at Enugu - Abakaliki – Ikom Highway Road, in South-East of Nigeria. The experimental program includes tests, routinely used in geotechnical engineering such as: Particle size distribution, Atterberg Limits, compaction, CBR, DCP and Mr. The interpretation of test results confirmed, DCP as a useful tool to determine CBR, resilient and unconfined compressive strength (UCS) values of an in-situ pavement structure. The predicted CBR values from AFCP-LVR software after DCP testing shows that laboratory soaked CBR value is averagely 1.6% lower. The predicted Mr values using AFCP-LVR software indicted a variation of 5.7 MPa on the average compared to measured Mr values.