The use of total station for monitoring mass movements: Application to fajãzinha landslide at flores island (azores archipelago)

Abstract

The present work has as study area a deep-seated landslide, which affects a significant part of Fajãzinha parish, on Flores Island (Azores Archipelago). This study is part of a monitoring project composed of hydrological, geotechnical and topographic components used to monitor a large slow movement with a depth surface of rupture triggered by rainfall. With the main goal of detecting small soil movements that precede larger instabilities, a geodetic monitoring programme was established using an automatic total station. In total 34 benchmarks were reobserved by an automatic total station Leica TM50 of 0.5”, with accuracy for distances of 0.6 + 1 mm. In this work, the total station data surveys are presented as well as the discussion of 27 campaigns carried out during the time span of 1 year (January 2018 until February 2019) to follow the evolution of the surface displacements. The maximum displacement rate observed in the area was about −57, 16 and −27 mm to E, N and Z component, respectively. The orientation of the displacement rate is compatible with the landslide that occurs in the area. Nowadays, this slope instability is confirmed by the slope geometry, ground cracks, and ground movement. This slow movement has caused, over the years, a number of disturbances to the inhabitants, due to damage to houses and structures, given the strong exposition of these vulnerable elements located on the body of the landslide.