METHODOLOGY FOR LANDSLIDE MONITORING IN A ROAD CUT BY MEANS OF TERRESTRIAL LASER-SCANNING TECHNIQUES

Abstract

After the heavy rains of 2009/10 winter, a road cut in the national highway A-44 and the upper slope became unstable; the mass invaded the way and caused important traffic interruptions by several months. The landslide was measured by means of terrestrial laser-scanner techniques and, because of the zone morphology, the used methodology involved scanning the mobilized zone from different stations with several captures from each point. Two scanning campaigns were carried out in a time interval of 14 days. The antenna phase centers were determined by GPS techniques and incorporated to the point clouds as an additional point in the TLS reference system; next, the relative orientation of the different point clouds of each scan station is made, adjusting and merging them in a single point cloud; finally, we proceed to data transformation to a reference system global and common to both campaigns, in which surface and terrain models can be compared. From field data, a digital surface model have been built, and then filtered and edited to have digital elevation models of centimeter spatial resolution. The results obtained by the comparison of models show two rupture zones in the road cut affecting also to the upslope, in which an important volume material flowed with superficial displacements of about 0,55–0,65 m day-1. We also calculated 210 m3 of depleted material and 124,5 m3 of accumulated material; the differences between these volumes (wasting material) are explained because the civil works that were made to clear the road of materials.