Determination of stiffness and other joint properties from roughness measurements

SummaryThe measurement of surface profiles is presented as a useful and simple approach to classifying statistically the essential features of rock joints. After introducing the reader to some existing analytical joint contact models for normal loading, a discrete numerical technique is developed. Using this technique the mechanical behaviour of a number of different slate joints is examined. The functional relationships between nominal stress, stiffness, true contact area and initial aperture are shown, for this class of joints, to be surprisingly simple. Experimental evidence is used to substantiate the numerical results. From the point of view of in-situ joint stiffness and hydraulic conductivity, numerical predictions seem feasible provided the degree of “mating” at some known stress level can be determined.