The design of multi-anchored tieback soldier pile walls in Sandton is typically based on either empirical methods or two-dimensional finite element modelling, ignoring the effects of matric suction in unsaturated residual granites. The designer, however, often relies on previous experience in a similar subsurface profile rather than established theory, to assess the ability of the soil to arch between soldier piles. Using experience rather than a sound theoretical basis for design could potentially be problematic. Excavations typically proceed in intervals between 1.5m and 2.5m before a reinforced shotcrete liner is applied. This differs from the way in which timber lagging is typically installed in smaller excavation lifts in the USA. In this study a typical Sandton residual granite profile is considered, and a matric suction profile estimated.
