Error Analysis of Sampling Spacing on Roughness of Rock Joint Based on Three Dimensional Laser Scanning Testing

The influence of different sampling spacing was investigated by applying the estimation of Joint Roughness Coefficient (JRC) and Profile Mean Angle (?_p) values based on the rock joint surface three dimension model. Laser scanner was employed to gather the original data of joint surface with sampling spacing of 0.001m. Then, according to the aforementioned data, the spline interpolation was introduced to generate all required data with whole range of sampling spacing from 0.00001m to 0.01m with an increment of 0.00001m. Both the JRC and ?_p values were calculated to estimate the roughness of samples. The results show that the JRC and ?_p values have a similar trend and increase with the decreasing of sampling spacing and reach an asymptotic value. Error of estimation of roughness was arisen from the sampling spacing variation, and the accuracy of estimation cannot always be improved by decreasing of sampling spacing. When the sampling spacing was reduced at around 0.00067m, there will be a slightly change on the JRC and ?_p values in term of shale rock joint samples collected from Jiwei Mountain landslide area.