Study on Influence of Joint Form on Flow in Rock Mass by Lattice Boltzmann Method

As a safety assessment of the geological disposal of high-level radioactive wastes deep in a rock mass, it is important to grasp the characteristic of permeability and mass transport. If the rock mass around a disposal site is crystalline material, joints can be involved in the rock mass. Since the cubic law of joint opening displacement is often used to evaluate flow properties briefly, it is necessary to discuss the applicability of the cubic law for the evaluation of flow properties. However, the complex-ity of joint form brings about the difficulty for the discussion of the applicability by an empirical method. Thus, in this study, a numerical approach is used for the discussion. As a method of numeri-cal approach, Lattice Boltzmann Method in which hydraulic gradient can be given as boundary condi-tions is employed. The influence of joint form on the flow property is examined through the Lattice Boltzmann analysis. In the result, it is clarified that the evaluation by the cubic law of joint opening displacement is valid from safety point of view although the hydraulic conductivity evaluated by the cubic law is slightly different from the numerical one. Furthermore, the flow through a joint is analyzed so as to reproduce the experimental flow test in which the distributions of opening displacement and geological form of the joint are grasped, and the analysis result is compared with measured one. In the result, the flow rate obtained from the LBM analysis is more closely to the measured one than that evaluated by the cubic law. Thus, it is founded that the evaluation of the flow through the joint involved in a rock mass by Lattice Boltzmann Method is more effective than the cube law.