Characterizing undrained shear behavior of loess subjected to K0 loading condition

Abstract

Undrained shear behavior of loess after the K0 consolidation was investigated through laboratory experiments. Both the monotonic and cyclic triaxial tests were performed on the intact loess samples retrieved from a construction site in Yan'an city, China. It was found that the coefficient of lateral earth pressure at rest (K0) of the intact loess is stress-dependent, and it varies between 0.46 and 0.85. Under the monotonic loading condition, the peak q in the undrained shear test is higher for the samples under the K0 consolidation than those under the isotropic consolidation. Besides, the cyclic loading tests were conducted on the loess samples subjected to different magnitudes of the initial deviatoric stress, including the K0 stress state. The test results revealed that different initial stress conditions cause distinctly different failure patterns. It includes the cyclic mobility with progressive development of the axial strain, and limited deformation followed by an abrupt gain of the axial strain with no precursor. In accordance to the build-up of the excess pore water pressure during the tests, each failure pattern of loess was interpreted in the q-p' diagram alongside the undrained instability state (UIS) line. The outcomes of this paper suggest a pressing need to thoroughly consider the K0 values of the intact loess with variations of the initial stress state.