Seismic stability analysis of cracked compound slopes considering soil heterogeneity

This study presents a seismic stability assessment framework for heterogeneous compound slopes with cracks, for example, highway embankment slopes. Based on limit analysis method, a kinematical approach incorporating a discretization technique is adopted to account for both global and local instabilities of cracked compound slopes under seismic excitations. The pseudo-static approach is applied to describe seismic forces. The soil heterogeneity is considered as linear variation along the depth. An implicit formula for stability factor (or safety factor) is derived through the work rate balance equation. The upper-bound solutions are calculated by combining a bisectional method with an optimization algorithm. The results are thoroughly verified through comparison with existing studies and finite element analysis. The results show that slope geometry plays a dominant role in governing slope stability and failure behavior. In particular, increasing the upper slope inclination significantly reduces the slope stability and induces a transition from local to global failure, especially under a larger depth coefficient. The presence of cracks further weakens slope stability, with their depth and location highly sensitive to geometric configuration. Furthermore, seismic excitation deepens cracks and shifts them upslope, inducing a transition from local to global failure as horizontal acceleration coefficient increases. Soil heterogeneity influences failure mechanisms that stronger upper soil deepens cracks via shear transition and shifts failure surfaces forward, exhibiting a "seesaw effect". The findings provide the guidance for the design of stable and crack-resistance slope engineering, particularly in topographically complex or geohazard-prone regions.