Sinkhole subsidence monitoring combining terrestrial laser scanner and high-precision levelling

Abstract

Sinkhole subsidence damage on transportation infrastructure is a particularly problematic hazard that has rapidly increased in numerous karst regions worldwide. The quantitative characterization of the deformation is fundamental for the design of effective mitigation measures and to prevent potential accidents. Nonetheless, there are a limited number of investigations addressing the monitoring of specific active sinkholes through the application of high-precision and high-resolution methods. Here, we present a sinkhole monitoring approach including the synergistic combination of high-precision levelling and high-resolution terrestrial laser scanner (TLS). The method has been satisfactorily tested in an active sinkhole affecting a railway corridor, which includes conventional and high-speed railway lines. The main outcome is the first example of low-error (±3 mm) 3D displacement models of an active sinkhole generated with TLS data without the use of ground control points. The methodological advance related to the 3D geometric alignment of successive point clouds without ground control points simplifies the logistics of TLS data collection and expands the potential sites where this technique can be applied, including non-accessible areas. The combination of geomorphological mapping and ground-penetrating radar provided critical data for sinkhole site characterization and design of the monitoring surveys. Subsequently, the integration of high-precision levelling and TLS data provided accurate information on spatio-temporal subsidence patterns (rates, kinematic style) and the precise location of the boundaries of the area affected by ground deformation in accessible and non-accessible zones.