Single phase water flow through rock fractures: Fid-Bau Portal

Single phase water flow through rock fractures

Indraratna, B. / Ranjith, P.G. / Gale, W.

Abstract Flow analysis plays a major role in various geotechnical applications, and the understanding of flow mechanisms is essential for the development of a hydro-mechanical flow model suitable for underground excavations in rock. Discrete flow analysis through discontinuities is reviewed including empirical and analytical flow models. The influence of external loading on joint deformation and single-phase flow show that the surface roughness and aperture size are the prime factors influencing flow rate. Nevertheless, the idealization of natural fractures as smooth parallel plate joints is still followed in many numerical models, because of the simplicity of the cubic law when applied to fracture networks. A numerical study of water flow through a network of joints employing Universal Distinct Element Code (UDEC) is used to quantify the effects of joint orientation and external stress acting on idealized joints. It is found that, for the same joint spacing, the flow rate into an excavation depends on the boundary block size ($ A_{b} $) relative to the excavation size ($ A_{e} $). The inflow becomes excessive if $ A_{b} $/$ A_{e} $ is less than 4, but becomes very small if $ A_{b} $/$ A_{e} $ exceeds 8.