Development of a shear-flow test apparatus and determination of coupled properties for a single rock joint

A new laboratory technique for coupled shear-flow tests of rock joints was developed and used to investigate the coupled effect of joint shear deforma tion and dilatancy on hydraulic conductivity of rock joints. This technique was used to carry out coupled shear-flow tests with an artificial created granite joint sample under constant normal loads and up to residual shear d eformations of 20 mm. The hydraulic conductivity was estimated by using a f inite difference method and an approximate equation assuming the cubic law. The shear-flow testing results revealed that the change of hydraulic condu ctivity is approximately similar to that of the dilatancy of a joint. The h ydraulic conductivity increases rapidly, by about 1.2-1.6 orders of magnitu de for the first 5 mm of shear displacement. After passing the residual she ar stress, the hydraulic conductivity becomes gradually a constant value wi th increasing shear displacement. On the other hand, the hydraulic conducti vity after shearing is about one order of magnitude larger than that prior to shearing. Shear-flow coupling characteristics obtained from these tests have a consistent trend with Barton's model prediction during the initial s hear process. However, increasing deviation between measured and predicted hydraulic conductivity of rock joint samples has been observed with increas ing shear displacement. (C) 1999 Elsevier Science Ltd. All rights reserved.