9.2.1 Excavation & repair
Excavation is a common method for improving the stability of a slope by reducing the magnitude of driving forces that contribute to movements. Unloading is a common technique to reduce the driving forces within a sliding mass. The lightweight (low density) fill materials can also be used to reduce the driving forces. This can also include removing weight from upper part of the slope (head), removing all unstable or potentially unstable materials, flattening and benching of the slopes (Figure 1). In general, rock removal is a preferred method of stabilization because it eliminates the hazard, and no future maintenance is required. However, this method is not effective where the rock is highly degradable, such as shale. In such circumstances, exposure of a new face initiates a new cycle of weathering and leads to instability. A more appropriate stabilization method for this condition is protection of the face with shotcrete and rock bolts, or a tied-back wall.
Figure 1: Stabilization of slope by removal and repairing the potential unstable blocks (TRB, 1996)