Failure mode analysis of jointed rock masses around underground opening under excavation unloading

Abstract

The failure modes and loosened mechanism for jointed rock masses around an underground opening under excavation unloading are studied using the discontinuous deformation analysis (DDA) method. A sequential excavation algorithm for jointed rock masses is proposed and implemented into the original DDA program. Different combinations of joint dip angle are used to study their effects on the failure modes and deformation behaviour of jointed rock masses. The results of both DDA and physical model show that the failure modes of jointed rock masses around the underground opening are mainly dependent on disadvantage combination of free excavating surface and discontinuities surfaces. The different joint orientations result in different failure modes and collapse areas of surrounding rocks. Opening and sliding failure in the left and right sidewalls of the underground opening occur for the orthogonal joint set with dip angles of 30×120°, while toppling failure was observed in the right sidewall for the joint set with dip angles of 45×135°.

Keywords:

• Discontinuous deformation analysis
• Failure mode
• Jointed rock mass
• Excavation

This research was substantially supported by the Natural Basic Research Program of China (973 Program, no. 2010CB732005), the National Natural Science Foundation of China (no. 50725931) and Natural Science Foundation of Hubei Province of China (no. 2009CDA149).