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

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