Pre-failure deformation monitoring as rockfall prediction tool

Abstract

In this article, we are elaborating an example of predictive rockfall assessment by using Terrestrial Laser Scanning (TLS) in monitoring a road cut, hosted in flysch rock formation, near Ljig in Serbia. A sequence of rockfall events from 2013-2019 is presented, while the cut has been more broadly investigated in our earlier work. Beside occasional rockfalls which are routinely detected by annual TLS monitoring, it was possible to track the pre-failure deformations preceding a series of rockfalls, reaching 0.3 m3 in volume with 0.5 annual reoccurrence probability. Monitoring enabled identification of subtle displacements of about 1 cm after the first event in 2014 and keeping track of its progression. After a series of events in the following years, we were able to define the pre-failure threshold which can be applied to the adjacent rock blocks, assuming a similar block volume. It also enabled us to anticipate and simulate the event before it happens. This approach allows planning, prevention and protection, and there is a great deal of interest to standardize it for high-risk slopes and cuts in rock masses.