Field tests on dynamic response and characteristics of lateritic soil subgrade under the combined action of wetting and cyclic loading

This paper aims at investigating the combined effects of wetting and traffic loading on the dynamic response of lateritic soil subgrade in the southern region of China. Vehicle tests involving four axle loads of trucks travelling at four speeds and vibration tests involving six repetitive vibration loadings were carried out in a test section of the Nanning–Zhanjiang expressway under three types of wetting conditions. The effects of wetting, vehicle speed, moving load, repeated loading, and loading numbers on the dynamic stress, dynamic acceleration, dynamic displacement, and accumulative deformation of the subgrade are investigated. The results show that under the effect of wetting, the dynamic response generated by the moving load on the subgrade increases, and excessive moving loads increase the dynamic response of the subgrade. The dynamic response of the subgrade exhibited exponential attenuation along the depth direction and transverse direction, and the influence depths were 2.3 m and 3.3 m for axle loads of 7 t and 30 t, respectively. At a depth of 0.3 m from the subgrade surface, the time–domain curves of the dynamic stresses are a double hump. The accumulative deformation rapidly increased and then gradually stabilized. When the loading was 3 million cycles, the accumulative deformation at the wetted twice stage was 16.8 % and 35.2 % greater than that at the wetted once and unwetted stages, respectively. The research results provide a reference for the structural design and safe operation of expressway subgrades in lateritic soil areas. •The effects of the varying moisture content and moving loads on the dynamic response of the lateritic soil subgrade along the depth and transverse directions are revealed.•The effects of the varying moisture content and repeated loading on the accumulative deformation of the lateritic soil subgrade are investigated.•The time-domain characteristics of the varying moisture content on the dynamic stresses and dynamic accelerations along the depth direction are concluded.