Surface roughness measurements using three-dimensional laser imaging

Three-dimensional (3D) laser imaging is capable of providing key information for rock mass characterization, in particular, surface roughness data. In an underground field trial, a controlled validation study is performed where orientation and surface roughness measurements are made manually and compared to laser measurements. From an acquired image, the 3D point cloud is used directly to make the measurements without the need for pre-processing. At each measurement location, the orientation of a particular joint is determined using principal component analysis which fits a plane to the point cloud data. The normal vector of the plane is used to determine the orientation of the joint. Next, the surface roughness is determined by plotting a 2D surface profile along the strike and dip. The maximum asperity amplitude is measured from the surface profile and the Joint Roughness Coefficient (JRC) is estimated.