Influence of fracture geometry on shear behavior

Laboratory research during the past 10 years has explained many critical li nks between the geometrical characteristics of fractures and their hydrauli c and mechanical behavior. One of the remaining research challenges is to d irectly link fracture geometry with shear behavior, including behavior in r esponse to changes in normal stress and shear direction. This paper describ es results from a series of shear tests performed on identical copies (repl icas) of a natural granite fracture, Based on these tests, we developed a m ethod using image processing techniques to identify and quantify damage tha t occurs during shearing. We find that there is a strong relationship betwe en the fracture's geometry and its mechanical behavior under shear stress a nd the resulting damage. Using a three-dimensional geostatistical model of the fracture surfaces, we analyze the dependence of the size and location o f damage zones on the local geometry and propose an algorithm for predictin g areas that are most likely to be damaged during shearing in a given direc tion. (C) 2000 Elsevier Science Ltd. All rights reserved.