Plane failure in rock and soil slopes is usually caused by the intersection of a discontinuity plane with a slope face. Typically, discontinuities are weaker than the surrounding intact material and provide a surface along which movement can occur. When designing a stable slope, it is often desirable to find the most critical conditions for a particular slope configuration and base the final slope design around those conditions. The worst case for most dry slopes usually includes a tension crack at a location determined by the slope geometry. The worst case for saturated slopes typically has a tension crack at the slope crest, providing the deepest tension crack, and a fully or partially dammed discontinuity. This paper focuses on plane failure analyses of compound slopes using limit equilibrium techniques. It provides new equations to calculate the position of a tension crack, water forces, and stability factor in compound slopes. The results of a compound slope and water pressures are illustrated through several examples.

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