Accumulative strain of clays in cold region under long-term low-level repeated cyclic loading: Experimental evidence and accumulation model

In cold region, the seasonal effects like changes in freeze–thaw should be investigated with respect to their influence on permanent settlement of foundation under long-term low-level repeated cyclic loading. Thereby, the influence of freeze–thaw processes on the accumulative axial strain of clays under long-term low-level repeated cyclic loading was investigated by conducting cyclic tri-axial tests and a numerical model for calculating the accumulative axial strain was proposed based on the experience observation in this paper. The normalized accumulative axial strain of clays increases significantly subjected to one freeze–thaw cycle, then decreases and tends up to be stable with the subsequent freeze–thaw cycles. The normalized accumulative axial strain increases with the increasing repeated cyclic stress amplitude, moisture content of samples and the number of loading cycles, but decreases with the increasing confining pressure. The modification parameters ηFT and functions fampl, fC, fW and fN were proposed to consider the effects of the influence factors and were implemented into the accumulative strain model. In this model, all of the calculating procedures were explicit and all material constants of clays were presented. Therefore, the accumulative strain model can be used to predict the settlement of foundation under long-term low-level repeated cyclic loading in cold region.