Accumulative deformation law and control of compacted lateritic soil under coupled action of wetting and dynamic loading

To address the problem that the in-service lateritic soil subgrade is prone to wetting and excessive additional deformation under the combined effects of traffic loading in southern rainy areas of China, the static triaxial tests with different moisture contents and the dynamic triaxial tests with different wetting times, wetting amplitudes and dynamic stresses are conducted. The effects of varying moisture contents on the cohesive force and angle of internal friction are analyzed, and the influences of dynamic stress amplitude, wetting times and wetting amplitude on the accumulative deformation and dynamic resilient modulus are investigated. A model for predicting the accumulative deformation is established by considering the dynamic stress amplitude, times and amplitude of wetting, cohesive force and angle of internal friction. Based on the spectrum method, a model for transverse isotropic dynamic response of lateritic soil is established. The validity of the analytical model is verified by comparing with the results of the field vehicle tests, and the law of vertical compressive strain on the top of subgrade is analyzed under the effects of wetting and dynamic loading. The results show that the accumulative plastic strain increases nonlinearly with the increasing dynamic stress amplitude, wetting times and wetting amplitude. The dynamic resilient modulus decreases with the initial moisture content and the wetting times. The vertical compressive strain on the top of subgrade increases approximately double after wetting of three times. The empirical relationship between the vertical compressive strain on the top of subgrade and the accumulative strain is established, and the control value of accumulative strain is proposed in combination with the existing specification of the permissible value of accumulative deformation of subgrade, which gives the controlling method for the deformation of lateritic soil subgrade. The proposed method is verified by the cement-treated upper roadbed filler and the dynamic resilient modulus tests in the test section of an expressway. The research results can provide reference for the design and service performance evaluation of durable subgrade in lateritic soil areas.