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 i nvestigation of the mechanical behavior of initially closely mated joi nts in rock undergoing small sliding displacements is undertaken. The goal is to elucidate important features of joint behavior such as dila tancy, damage of surface roughness, cyclic sliding behavior and the de pendence of these phenomena on stress level and sliding history. Testi ng was carried out in a specially designed and fabricated servo-contro lled direct shear machine. Most tests employed artificial joint sample s with saw-tooth shaped asperities molded of hydrostone which replicat es soft natural rock. Use of molded samples allowed tests to be conduc ted on simulated joints which for our purposes, could be considered to be identical. Tests on natural joints in dolomite were also carried o ut. This testing program provided the guidance and data base necessary for the development of a quantitative theory and constitutive model f or rock joint behavior, which is described in Part II.