In order to evaluate the change in the hydraulic conductivity by excavation in a fractured rock mass, the nonlinear elastic model is proposed. The crack tensor theory originally proposed by Oda and the nonlinear elastic model of fracture proposed by Baton and Bandis are combined in the continuous coupled hydraulic and mechanical model. The model is applied to the in-situ tests that investigate the effect of the excavation on the hydraulic and mechanical characteristics. The comparison between calculated and measured results shows that the proposed model can predict the hydraulic conductivity change due to excavation in the case that the fracture geometry information is obtained appropriately, and that the mechanical behavior can be represented well by the model.
Excavation in the fractured rock mass is one of the most important construction process for several projects, e.g., oil storage cavern, LPG storage cavern, underground power plant, CAES plant and high-level radioactive waste disposal project. The change in hydraulic conductivity due to excavation has a large effect on the function of such structures. It is, however, very difficult to predict the change in hydraulic conductivity due to excavation because many factors are interacted complicatedly. In this paper, the new approach to predict the coupled deformation and seepage phenomena in the fractured rock mass is presented. To introduce the anisotropy of the mechanical and hydraulic properties, the crack tensor theory originally proposed by Oda (1986) is applied. This theory can use the fracture geometry information similarly to the discontinuous model such as FracMan (Dershowitz, et al. 1994). The anisotropic phenomena can be realized by this theory well (Kobayashi, et al. 1997). The nonlinear behavior of a fracture has been modeled by Barton-Bandis model (1985) in many cases. This model is made from the results of many experiments.
