The stability of wedges formed by three intersecting discontinuities in the rock surrounding underground excavations

A new method has been developed to calculate the three dimensional geometry of wedges formed by three intersecting structural discontinuity planes in the rock surrounding an underground excavation, and to analyze the stability of these wedges. The cross section of the underground excavation can be any arbitrary shape and the excavation can be oriented in any direction. The method can identify a maximum of six wedges around the underground excavation and determine the mode of failure and safety factor of each identified wedge. After rock bolts have been installed to support these potentially unstable wedges, the new modes of failure can be determined and the new safety factors can be recalculated.; The method has been incorporated in a user-friendly computer program named UNWEDGE--stability analysis of underground wedges. This program performs the three dimensional geometrical calculations and the analysis of wedge stability. It also enables the user to visualize the geometry of the wedges by means of three dimensional computer graphics, to define the excavation section and to install the rock bolts interactively.