Effect of different water contents on the softening characteristics of clay under intermittent cyclic dynamic loading

Dynamic triaxial tests were conducted to investigate the occurrence of intermittent periods and the effect of different moisture contents on the cumulative plastic strain and softening characteristics of clay under cyclic dynamic loading. The scaling factor of the Weibull distribution is regarded as the loading time parameter, and the shape factor is regarded as the moisture content parameter. Based on the clay softening index and Weibull distribution function, a clay softening model varying with loading time is constructed. The failure prediction and shear modulus attenuation can be analyzed by the softening model. The test results reveal that the cumulative plastic strain mainly develops during the first loading period, and this intermittent period leads to strain rebound and reduction in the final cumulative plastic strain in clay. Different water contents change the growth amplitude and growth rate of the plastic strain curve, with the lowest growth amplitude and rate occurring at the optimum water content. The shear modulus shows a decreasing trend of slow decay at the first stage and rapid decay at the later stage. The loading-interval-reloading mode redevelops the decay rate of the shear modulus at the initial stage of each loading period. The effect of moisture content on the softening characteristics of clay is shown in two parts: the difference in the initial shear modulus and the difference in the attenuation curve. The attenuation ratio of the shear modulus of clay with an optimal moisture content is the smallest, and the attenuation range is the largest.