Excavation design in jointed rock

Abstract

A jointed rock mass presents a more complex design problem than considered previously. The complexity arises from either the number (greater than two) of joint sets which define the degree of discontinuity of the medium, or the presence of a discrete structural feature transgressing such a simply jointed system as a cross-jointed, stratified mass. The problem which arises in these types of media is the generation of distinct rock blocks, of various geometric configurations defined by the natural fracture surfaces and the excavation surface, as illustrated in Figure 9.1. Since the blocks exist in the immediate periphery of an excavation, whose surface has been subject to the removal of support forces by the mining operation, the possibility arises of collapse of the block assembly in the prevailing gravitational and local stress fields.