Characterization of Sheeting joint roughness of Hong Kong Granite using 3-D Laser Scanning Technique

Abstract

In rock slope design, the mobilized frictional angle of rock joint roughness depends on basic frictional angle, small-scale roughness and large-scale waviness. If the shearing surface is wavy and the unstable block size is large, it would greatly affect the adoption of representative parameters for the design of the overall stability of a rock slope. Automatic 3-D laser scanning unit is now available that can be used to record 3-D coordinates of closely spaced points representing the rock surface. After the rock surface is 3-D scanned, it can be transformed into a triangulated irregular network representing the continuous wavy surface of the rock. Dimensionally accurate surface profile and pictorially correct images can then be generated and the asperities height and angle can be assessed at different sample sizes. The use of automatic 3-D laser scanning technique with the incorporation of photo images would allow fast and accurate determination of representative roughness profile of different sizes of rock surface, thus the effect of small-scale roughness and large-scale waviness can be differentiated and determined. This paper describes the scale effects of surface roughness and report the large-scale waviness of typical sheeting joints of Hong Kong Granite using the 3-D laser scanning technique.