A method for automated discontinuity analysis of rock slopes with 3D laser scanning

This paper describes the interim results of a study to characterize discontinuous rock masses using 3D laser scanning data. One of the main advantages of this method is that now an unbiased, rapid and accurate discontinuity analysis can be done. With 3D laser scanning it is now also possible to measure rock faces whose access is restricted or rock slopes along highways or railway lines where working conditions are hazardous. It is also shown that the proposed method will also be cheaper than traditional manual survey and analysis methods. Laser scanning is a relative new surveying technique, which yields a so-called ‘point cloud’ set of data, where every single point represents a point in 3D space of the scanned rock surface. Since the density of the point cloud can be high (in the order of 5 mm to 1 cm), it allows for an accurate re-construction of the original rock surface in the form of a 3D interpolated and meshed surface, using different interpolation techniques. Through geometric analysis of this 3D mesh and plotting of the facet orientations in a polar plot, it is possible to observe clusters, which represent different rock mass discontinuity sets. With fuzzy k-means clustering algorithms individual discontinuity sets can be outlined automatically and the mean orientations of these identified sets can be computed. Assuming a Fisher’s distribution it is subsequently demonstrated that the facet outliers can be removed. Finally, it is shown that discontinuity set spacings can be calculated as well.