Distributed optical fiber sensors and terrestrial laser scanner surveys for the monitoring of an underground marble quarry

Abstract

The sensing applications nowadays are always more used for structural and engineering-geological applications. In this work, an experimental monitoring system of an underground marble quarry, located in the Apuan Alps (Tuscany, Italy) is presented. The system is composed by Distributed Optical Fiber Sensors (DOFS) based on Brillouin Frequency Shift (BFS). By using a control unit, multitemporal data of strain and temperature were measured thanks to the installation of 250 linear meters of DOFS placed around two pillars. Terrestrial Laser Scanning (TLS) surveys, aided by GNSS (Global Navigation Satellite System) and TS (Total Station) measurements, were executed with the aim of: i) identifying physically inaccessible rock joints (i.e. height of the pillars), ii) georeferencing the DOFS and, iii) locating any strain phenomenon. The integration of a DOFS monitoring system with geomatic technologies has given the possibility to initialize a real-time monitoring system aimed at protecting the safety of the workers from possible rocky wall collapses. The results obtained in this work are the texturized 3D model of the analyzed pillars, the DEM and the orthophoto of the quarry, and the profiles of BFS, strain and temperature variation. This research was funded by Tuscany Region (Italy) though the POR FESR 2014-2020 plan.