Forecasting and Mitigating Rockfall based on Lidar Monitoring: A Case Study from Colorado

Abstract

It is well-established that precursor movement that precedes large rockfalls can be detected by monitoring using repeated laser scanning (i.e., lidar), but there is a lack of documented cases that illustrate the practical application of this technology to forecast and help prevent large rockfalls along transportation corridors. In this paper, we present a case study in which routine lidar monitoring allowed a large (∼30 m³, ∼1050 ft³) moving block of rock to be detected before failure. Analysis of the lidar data allowed for historical movement to be evaluated, time to failure to be estimated, and quantification of the geometric and structural data necessary to design an effective mitigation scheme. The block movement was interpreted to be associated primarily with a planar sliding mechanism, and a limit equilibrium analysis was conducted to evaluate potential reinforcement schemes. Ultimately, a mesh and pattern bolt reinforcement system was installed. During rockbolt tensioning, PVC extensometers installed by the contractor showed closure of the fracture at the back of the block.