AN INVESTIGATION OF THE MECHANICS OF ROCK JOINTS .1. LABORATORY INVESTIGATION

In this paper, which is the first of a two-part series, a laboratory investigation of the mechanical behavior of initially closely mated joints in rock undergoing small sliding displacements is undertaken. The goal is to elucidate important features of joint behavior such as dilatancy, damage of surface roughness, cyclic sliding behavior and the dependence of these phenomena on stress level and sliding history. Testing was carried out in a specially designed and fabricated servo-controlled direct shear machine. Most tests employed artificial joint samples with saw-tooth shaped asperities molded of hydrostone which replicates soft natural rock. Use of molded samples allowed tests to be conducted on simulated joints which for our purposes, could be considered to be identical. Tests on natural joints in dolomite were also carried out. This testing program provided the guidance and data base necessary for the development of a quantitative theory and constitutive model for rock joint behavior, which is described in Part II.