Inclinometer Measurements with Robotised and Traditional Mobile Probes in Extremely-Slow Landslide

The movements of a large, extremely-slow, deep-seated landslide interacting with a viaduct of the E45 highway (Province of Bolzano, Northern Italy) have been monitored since 2006. The landslide is an active block of a Multiple Rotational Rock Slide (MRRS). It has a planimetric extension of 400 m x 400 m, a maximum depth of the sliding surface of about 50 m, a total estimated volume of 6 Mm3. Subsurface displacements have been monitored using a traditional, portable, manually-operated probe inclinometer; those of the piers of the viaduct by total station. These measurements have been carried out periodically, 2 to 4 times per year. Redundancy analysis showed that the measurements are reliable, and the mean yearly velocity is less than 10 mm/y. Since December 2019, the Automated Inclinometer System (AIS) was installed in one of the eight inclinometer tubes to robotise manual measurement operations and provide higher-frequency measurements (about one dataset per day). This paper discusses the advantages of the robotised, higher-frequency measurements provided by the AIS compared with the manual, lower-frequency measurements from the traditional manually-operated probe, in terms of: semi-checksum verification, time required to identify the depth of the sliding surface and evaluate the displacement rate for an extremely slow landslide, and ability to recognise its seasonal trend