A three-dimensional (3D) kinematically admissible rotational failure mechanism is extended from toe failure to include face failure and base failure for homogeneous slopes in both purely cohesive and frictional/cohesive soils. In the strict framework of limit analysis, an analytical approach is derived to obtain the upper bounds on slope stability and the corresponding type of the critical failure mechanism. Compared with the available results from the finite-element limit-analysis method, the 3D rotational failure mechanisms give the best estimate on the upper bound. A set of stability charts is presented in a wide range of parameters for 3D homogeneous slopes under both static and pseudostatic seismic loading conditions. This set is useful in assessing the safety of the 3D homogeneous slopes in practical applications.

A series of isotropically consolidated undrained triaxial tests were performed on cemented clay with super-absorbent polymer (SAP) at high water content to investigate the effect of SAP content on the undrained shear behavior of cemented clay. The test results reveal that the compressibility and undrained shear strength of cemented clay with SAP in a preyield state are independent of the confining pressure. When the confining pressure is higher than the yield stress, the compressibility of the cemented clay with SAP increases dramatically. Meanwhile, the undrained shear strength of the cemented clay with SAP depends on the confining stress in the postyield state. The yield stress measured from the isotropic compression test is consistent with the transitional stress from the bilinear relation between the peak deviator stress and the confining pressure. For certain lime content, the role of SAP is to increase the cementation bond. Hence, the peak deviator stress increases with the increasing SAP content, lime content, and curing time. However, the cementation is shown to have no effect on pore pressure generation within the degree of cementation considered in this study. The linear failure envelope of the cemented clay with SAP is observed for the range of applied stress level in this study and is bounded by the tension cut-off and the critical state line of untreated clay. The difference between the failure line of cemented clay and the critical state line of untreated clay increase with the degree of the cementation bond (i.e., higher SAP content, higher lime content, and longer curing time).