Importance of joint behaviour on potential water inflow into underground structures

Problems related to fluid flow through fractured rock masses have led to an increased awareness of the sensitivity of many rock engineering projects to their particular hydrological conditions. In most crystalline rock masses, the fracture conductivity generally exceeds the primary permeability by several orders of magnitude. Originally, discrete models for fractured media assumed the fracturers to be rigid, but later research has shown that fracture deformability is an important fluid flow parameter. The present study utilizes existing models to study flow in dilatant fractures and attempts to define the range of influence of fracture deformation on conductivity and the limitations of the discrete approach. The model is based on a rather straightforward coupling of dilatancy and conductivity. The results indicate that dilatancy may be the most central parameter affecting conductivity in deformable fracture flow. The implications of the results on the design and performance of a number of field investigations and engineering structures are discussed. (author)