The use of terrestrial LIDAR in determining directional joint dilation angle values

It is well documented in the field of rock mechanics engineering that joint roughness plays an integral role in the shear strength of discontinuities. The effective friction angle of a discontinuity includes both the saw-cut friction angle, φ, and the inherent natural roughness encountered on fracture faces. This second component is the joint dilation angle, and is the focus of this study. Emphasis is not on a preferred method of characterizing roughness, but rather a new technology as a tool to assist in analyzing joint roughness. Using ground-based laser scanning and point cloud processing software, joint dilation angles can be found by finding the angular difference between poles to a triangulated mesh and the mean pole. Simple vector operations can then project all poles onto a common surface (the fracture surface) and described as rakes on the plane. These two components make up the directional dilation angle, which seems to be a valid took based upon a case study performed at a site near the San Pedro Vista near Tucson. This directional dilation angle value may influence the directional shear strength, for example in a direction parallel to a dip direction of a joint. Future research will also include analyzing the relationship between this directional dilation angle and the overall structure of the rock mass in which it is found.