ABSTRACT
This chapter discusses the various large-scale and small-scale stability problems that can occur in rock, including instability of excavation side slopes and bases. The concept of groundwater management in excavations was introduced and is essentially the approach of ‘dewatering’ an excavation by removing the groundwater that enters, without considering the destabilizing effect of groundwater seepage into the excavation. While groundwater flow within fractures is important in almost all rock types, if the rock matrix is potentially porous and permeable, then the flow system may be ‘dual porosity’, where groundwater flow occurs both in fractures and in the rock mass itself. The groundwater flow in the sandstone is dual porosity and occurs in a combination of closely spaced fractures and intergranular flow through the rock matrix. Groundwater control projects in karst aquifer conditions are at risk of very high pumping rates, particularly if significant networks of permeable solution features are in the zone affected by the project.
