Discontinuity network modeling of the rock mass around a tunnel close to the proposed permanent shiplock area of the three gorges dam site in China

Discontinuity data of a 400 m tunnel located close to the proposed shiplock area were investigated to characterize the discontinuity geometry of the rock mass around the tunnel. Traces of 39 major discontinuities (faults and dykes) were found on the tunnel exposures. Over 2000 minor discontinuity (joint) trace data available showed that the rock mass can be separated into about 5 statistically homogeneous regions. Three to four joint sets were found to exist in each of these regions. Available theoretical probability distributions were found to be insufficient to represent the statistical distribution of orientation of joint clusters. For more than 94% of the joint sets, gamma distribution was found to be the…