Numerical study on zonal disintegration of rock mass around deep underground openings

With mining activity developing to deeper area, a failure mode called zonal disintegration (ZD) has been found. That is, after excavation, there were some alternating regions of fracture zones and relatively intact zones around or in front of the working face, which is quite different from the traditional understanding of rock failure mode. A three dimensional numerical model is applied to simulate the zonal disintegration phenomenon. Results of numerical simulation show that a higher compressive stress along axial direction of the openings does cause the occurrence of ZD phenomenon, but only under a certain boundary condition. The fracture rings are neither closed rings nor continuous one both in the radial and axial direction. The propagation of ZD is in a spiral way around openings. Most of the fracture zones occur in the area of brittle rock mass with high strength and high elastic modulus. For parallel closed-spaced openings, in the vicinity of openings, the fracture rings enclose each opening separately; with the increasing of distance from the opening periphery, the fracture rings enclose the two openings. The distance between each two fracture rings and the number of fracture rings have close relation with the heterogeneity of the rock mass.