Stiffness evaluation of compacted geo-materials using crosshole-type dynamic cone penetrometer (CDP), rPLT, and LFWD

Evaluation of the strength and stiffness of compacted geo-materials is required to ensure that it has sufficient bearing capacity and stiffness to the acting loads. In this study, a crosshole-type dynamic cone penetrometer (CDP) was applied to investigate the strength and stiffness characteristics of a compacted subgrade. The CDP characterizes the subgrade strength by the penetration index (CDPI) and evaluates the stiffness by the shear wave velocity (V_s) and maximum shear modulus (G_max). CDP tests were conducted at three testing points. Repetitive plate loading tests (rPLTs) and light falling weight deflectometer (LFWD) tests were conducted as standard testing methods for the stiffness estimation of the subgrade. Experimental results show that while the rPLT and LFWD evaluate the equivalent elastic moduli (E_v1, E_v2, and E_vd) within the influence zone, the CDP provides the CDPI, V_s, and G_max along the depth. Linear relationships between the G_max and the equivalent elastic moduli are constructed. The strain levels corresponding to E_v1, E_v2, and E_vd are estimated. This study demonstrates that the CDP is an effective testing method for both strength and stiffness evaluations of the subgrade along the depth.