The paper studies the effects of such factors as soil types, layer thickness and soil strength etc to slope avalanche, preliminarily analyses the variation trend of soil intensity parameters following grain composition, water capacity, soil density and clay content Based on critical slope experiments, a formula about safety coefficient for distinguishing slope stability is given: F=K f (1-ω/ω L)(tgφ/tgβ+ c/ γ sH)
According to the principle of seepage force, equation for stability of earth slope under seepage condition is established, and reasonableness of the method is verified by engineering example. The method can be of reference value for analysis of earth slope engineering.
Both classical methods of soil slices and current various methods of soil slices suppose the stability of all individual slices equal to the stability of slope. However, the analysis results only can ensure the whole slices system to up to condition of limit balance but not individual slices, so these methods belong to unclosed limit balance method of rigid.
This paper follows the analytical way of studying the unsaturated slope: "rainfall →variety of the moisture content →variety of the suction →variety of the shear strength →stability of slope" to study the unsaturated slope, mainly focus on the part "rainfall →variety of the moisture content →variety of the suction" .
Based on the theory of upper bound limit analysis,the velocities of the nodes are regarded as unknown quantity,with the conditions of flow rule,velocity discontinuity,velocity boundary,the energy-work balance equation,the linear programming model of stability of slope subjected to pore water pressure are established. The pore water pressure is considered as an external force.