A macro-meso nonlinear strength criterion for frozen soil

Different from other geotechnical materials, the strength characteristics of saturated frozen soil have nonlinear characteristics that first increase and then reduce with the increasing confining pressure, and are sensitive to varying temperature due to the existence of ice inclusions. Based on analysis on the breakage of frozen soil, it is believed that the proportion of each material component and ice-soil cementation breakage are the internal mechanisms to control the macroscopic strength. On the basis of this analysis, a multiscale strength criterion is proposed to account for this coupling mechanism. Firstly, the linear strength criterion of soil skeleton and ice inclusions in broken/unbroken states are defined, based on which the strength criterion of the bonded elements (unbroken material aggregate) and frictional elements (broken material aggregate) are deduced through the yield design theory and linear comparison composite. Secondly, the failure of ice-soil cementation is reflected by the transformation of the bonded elements to frictional elements, thus the multi-scale nonlinear strength criterion of representative volume element is derived by combining the binary medium model and strength homogenization method. These results have been verified by the test results of different types of saturated frozen soils.