Terrestrial laser scanning used to determine the geometry of a granite boulder for stability analysis purposes

In this paper we analyze the use of terrestrial laser scanning (TLS) technologies to determine the geometric features of a granite boulder. Accurate determination of these features is a key to performing a reliable stability analysis of the boulder.TLS has been demonstrated to have important advantages over traditional measurement techniques—such as, for example, direct methods based on the use of tapes or indirect methods such as topography or close-range photogrammetry. TLS equipment enables thousands of points to be accurately measured in minutes. In our study TLS-measured points were used to model the surface of a boulder. Geometric parameters were then calculated, namely, centre of gravity, volume of the boulder and dimensions of the boulder contact area with the ground. Taking into account mechanical and environmental factors, these parameters were used to calculate the safety factor of the boulder against toppling and sliding. Our results show that, when seismic activity in the region is taken into consideration, the boulder is borderline stable–unstable.