What Setup for a TML Survey? The Experience Along the A22 Motorway (South Tyrol, Italy)

This work presents the comparison of different terrestrial mobile LiDAR (TML) survey’s setups tested to monitor the potential rockfall detachment zones along the A22 motorway. The study area covers a 13 km-section of the motorway, between Bolzano Nord and Chiusa (South Tyrol, Italy), where the motorway runs on cut-fill roads and viaducts at the toe of rock cliffs in the Isarco River valley. In this area, a rockfall hazard analysis identified 27 potential detachment zones, and a sample of 19 zones has been used to verify the effectiveness of a TML survey from a car running on the road. Different settings of the LiDAR (i.e. high or low sampling frequency, maximum or minimum range) and different vehicle speeds from 20 and 70 km/h were used. The present study provides details on the various TML survey setups and compares their results to identify the most effective for detecting the potential detachment zones along a motorway. The effectiveness of the TML is evaluated in terms of the percentage of detected rock slopes and superficial point density achieved in the 19 potential rockfall detachment zones. In addition, the TML survey ability to identify rock discontinuities is explored for a portion of rock slope.