Detection of roadbed layers in mountainous area using down-up-crosshole penetrometer and ground penetrating radar

The characteristics and depths of the old roadbed layers must be assessed for the serviceability and rehabilitation of aging road pavements. This study's objective is to detect roadbed layers in mountainous areas using the obtained stiffness profile and ground penetrating radar (GPR) results. Down-up-crosshole penetrometer (DUCP), GPR, and light falling weight deflectometer (LFWD) tests were conducted to determine the overlay, surface, base, subbase, antifrost, and subgrade layers. The results show that the dynamic cone penetration index DCPI, shear modulus calculated by the shear wave velocity, and GPR image capture each layer. The elastic modulus estimated by the shear modulus is corrected by considering the strain influence factor and matches the LFWD modulus, despite the ranges of values differing owing to the disparate strain level. Therefore, the DUCP can be applied to roadbeds in mountainous areas to assess the stiffness at each layer as well as to detect the layer interface.