Abstract
This paper describes the simulation method to explain the mechanism of the permeability characteristics of specimens with single discontinuties under shear through shear-flow coupling tests, showing that on the shear stress-displacement curve obtained by the constant normal load testing, the water flowing through the discontinuties have different transmissibility-aperture width relation before or after the yield range. As a technique to serve this purpose, the lattice gas automaton method, which is to substitute the fluid with particles and repeat letting them collide. With this technique, the factors of surface structure of discontinuties that determine the shear/permeability characteristics are identified.