C3 Soil slope stabilization
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
Figures & Tables
This book provides a complete guide to the study, design, construction and management of landslide and slope engineering measures for mountain roads, with an emphasis on low-cost. The geographical focus of the book is on the tropics and sub-tropics, but is also highly relevant to other regions where heavy rain, steep slopes and weak soils and rocks combine to create slope instability. The causes and mechanisms of landslides are described, and the hazards they pose to mountain roads are illustrated. Methods of desk study, field mapping and ground investigation are reviewed and illustrated, with an emphasis on geomorphological and engineering geological techniques. The design and construction of alignments, earthworks, drainage, retaining structures, the stabilization of soil slopes and rock slopes, and the control of erosion on slopes and in rivers and streams are covered. Slope management as part of road maintenance and operation is reviewed, and procedures for risk assessment and works prioritization are described.