Influence of fracture geometry on shear behavior

Laboratory research during the past 10 years has explained many critical links between the geometrical characteristics of fractures and their hydraulic and mechanical behavior. One of the remaining research challenges is to directly link fracture geometry with shear behavior, including behavior in response to changes in normal stress and shear direction. This paper describes results from a series of shear tests performed on identical copies (replicas) of a natural granite fracture, Based on these tests, we developed a method using image processing techniques to identify and quantify damage that occurs during shearing. We find that there is a strong relationship between the fracture's geometry and its mechanical behavior under shear stress and the resulting damage. Using a three-dimensional geostatistical model of the fracture surfaces, we analyze the dependence of the size and location of damage zones on the local geometry and propose an algorithm for predicting areas that are most likely to be damaged during shearing in a given direction. (C) 2000 Elsevier Science Ltd. All rights reserved.