A model coupling discrete and continuum fracture domains for groundwater flow in fractured media

Abstract

Fractures in a rock mass are divided into dominant fracture systems and network fracture systems. This paper presents a discrete and continuum medium approach to describe fluid flow in dominant fracture systems and network fracture systems, respectively, and these two are coupled by hydraulic head and flux. The coupled model simulates one-by-one fluid flow in dominant fractures that are major water transport conduits in a rock mass. It avoids calculating fluid flow in numerous individual network fractures but treats them as an equivalent porous medium instead. In this way, the approach can not only describe contribution of individual dominant fractures in ground water transport but also be applicable for the problem of large-scale and long-term simulation. The paper considers also the effect of some important factors on ground water flow in relation to hydropower projects, such as drainage pipes, pumping wells, drainage wells and well screens, and rainfall infiltration from flood discharge. The finite element method is applied to obtain the numerical solutions of the model. Results of theoretical test calculations indicate that the model represents effectively ground water flow in rock fracture systems. A case study in Wujiang Goupitan Hydroelectric Power Station indicates that it is an effective approach to analyze ground water flow in rock fracture systems of reservoir regions.