Abstract:

Slope stability charts offer a rapid and efficient alternative to the iterative method for assessing the stability of two-stage soil slopes. Employing the upper bound theorem of limit analysis,the global and local failure mechanisms were constructed for two-stage soil slopes. By incorporating the pore water pressure coefficient r_u,the expressions for internal and external work rates of the failure mechanism were derived,and the relationship curves between c/(γH) and tanφ for two-stage soil slopes in ultimate equilibrium state were obtained,referred to as the limit state curve (g-line). Based on this g-line,a series of two-stage soil slope stability charts were developed. The validity of these charts was confirmed through comparative analysis,and the effects of slope pore water pressure,geometry,and internal friction angle on slope stability and failure modes were systematically investigated. Results reveal that pore water pressure leads to the outward shift of the limit state curve,reducing slope stability. The failure mode of slopes is significantly influenced by their geometric shapes: convex and concave slopes are susceptible to local failures,with the extent of local failure expanding under the influence of pore water pressure. Additionally,as the internal friction angle of soil increases,the critical sliding surface shifts toward the slope surface,transitioning from global to local failure. The developed slope stability charts enable the simple and rapid evaluation of slope’s safety factors and corresponding failure modes,providing a valuable reference for stability assessments in similar slope engineering projects.

Key words: slope stability, factor of safety, pore water pressure, stability chart, limit analysis