Partially submerged slopes have long been of interest in civil engineering and classical analysis has produced charts for the assessment of their stability. However, these are limited in real applications due to restrictions on geometry, simplified soil properties and "a priori" assumption of the mechanism of failure. In contrast the finite element method allows complete flexibility of approach and can model more complex problems involving partial submergence, all drawdown conditions and variable face loadings. This paper considers these advantages for a range of problems and in particular the analysis of rapid drawdown from full and partial submergence.
Partially submerged slopes are of engineering interest both where they occur naturally and where designed. Naturally occurring slopes demonstrate the influence of water on the soil's material strength in that they have usually assumed a stable condition under repeated submergence and drawdown. None the less, analysis of an existing slope may be needed when work is to be carried out requiring excavation, steepening or extension of the slope. Where existing material properties are variable or virgin material is to be introduced to an existing slope, classical methods are extremely limited in their application. The ability to model any slope geometry, a range of materials in an inhomogeneous problem and an infinite variety of water level and additional face loading is unique to the finite element (FE) method. A finite element slope stability program, FEEMB1LG, implemented here illustrates these capabilities. Internal water conditions The strength of a soil, in terms of its ability to resist applied loading, is a function of its" effective stress state. This, in turn, depends on the pore water pressure (pwp) at each point. Pore water pressures may be derived from historical conditions (especially in fine-grained materials) or measured in current conditions (usually in coarse-grained materials).