the effect of sampling interval on estimated joint roughness coefficient by statistical parameters

In this paper the original barton’s profiles digitized with various sampling interval (si) from 0.1 to 1 mm and then the joint roughness coefficient (jrc) values estimated by statistical parameters such as: z2, z3, sf, rp, rq, rp-1, ra and ra. for this purpose, the polylines of typical roughness profiles (except the first profile) retraced and scaled to 10 cm in length in the autocad software, where each polyline contained more than hundreds points (si=0.1-2.0 mm), which satisfy the precision requirement of roughness characterization. next, the original polylines were imported into a matlab program written by the authors, in which the roughness profiles were redrawn at a fixed sampling intervals. then, the obtained jrc values by mentioned statistical parameters compared with each other. the highest and the lowest sensitivity to si were given by z3 and rp, respectively. all of these results clearly indicate that the jrc values are dependent on the sampling interval. it is also shown that a single statistical parameter is insufficient to represent the roughness of rock joints and the relationship between jrc and statistical parameters is generally nonlinear.