C3 Soil slope stabilization

Abstract

This section focuses on techniques of soil slope stability analysis and stabilization and provides selected case studies to illustrate some of the approaches commonly adopted. The first distinction to make is whether the materials forming the slope under consideration behave primarily as soil or rock. A soil slope will fail through its granular mass, whereas a rock slope (Section C4) usually fails principally along discontinuities (bedding, foliation or other joints). Relict joints may be present in soil weathering profiles, associated with the original rock structure (Section A3.1). These normally have a weakening effect and, if adversely orientated, may become preferred planes of failure. In practice, a clear distinction between soil slopes and rock slopes cannot always be made. As described in Section A3, rock structure, weathering profiles and taluvium/colluvium deposits on mountain slopes can be highly variable; it is not uncommon to find that a given slope will fail partly through rock and partly through soil. In in situ weathered soil profiles it is often the weathering grade boundaries, for example between weathering grade III and IV and IV and V, that tend to form the basal slip surfaces of shallow rainfall-induced landslides in the humid tropics and subtropics. However, in weathering grade I–III rock, the presence of jointing, folding and faulting often results in the development of complex weathering and strength profiles to the extent that zones of ‘rock’ with strengths not much greater than that of soil may be present at considerable depth (as illustrated in Sections B4 & B5). This will often exert significant control on the depth and configuration of existing or potential failure surfaces. ### C3.2.1 Ground model Before a slope stability assessment or analysis is made it is first necessary to establish a ground model. This is a normal progression from the field mapping and ground investigation activities …