Developing a technology of driving and supporting mine workings in tectonically weakened rock zones

Abstract

Presence of tectonically weakened and disturbed zones leads to decreased underground excavation rates and reduced safety of the mining operations. As a rule, such zones are bounded by vertical and subvertical disturbances that contribute to weakening and loss of stability of the rock and ore mass. Disturbance of the natural state, in particular driving of a mine workings, provokes irreversible deformations due to redistribution and concentration of stresses within the boundary rock mass, which is more rigid. At the same time no significant stresses are formed within the rock mass of the tectonic zone due to its caving. Therefore, when developing solutions for driving and supporting mining excavations within the tectonic zone, the rock mass should be considered as weakened and highly fragmented with unbonded structural blocks. The particle-size distribution within the rock mass of the tectonic zone varies in a wide range of sized from several to tens of centimetres. In this context, the mining and rock reinforcement technology presented in this paper accounts for the possible free caving of the non-bonded host rock mass made up of small-sized blocks. The paper discusses physical and mechanical characteristics and the stress-and-strain state of the rock mass within the tectonically weakened zone and the boundary host rocks, and a technology of driving and supporting underground mine workings is proposed on this basis.