3D Laser Mapping Offers Rockfall Analysis

46 Rockfall 150

46 Rockfall 4003D Laser Mapping released its laser-based geotechnical monitoring system, SiteMonitor4D, in 2004. Designed to monitor and quantify changes to the rock face, SiteMonitor4D automatically alerts mine safety managers via email or SMS when issues arise.

Since 2004, the range and resolution of commercial laser scanners have improved significantly, which offers an opportunity to improve the failure prediction in the SiteMonitor software. The compny began an innovative research project with Durham University in 2013 exploring the benefits of using rockfall analysis as a predictor of failure.

Based on the results of a project where laser scan data was collected for 100,000 sq. m of coastal cliffs over an eight-year period, the resolution of the scan data was 0.01 m and the volume of all the rockfalls (small and large) were quantified by volume. The smallest detectable rockfall was 0.00001 cu. m.

This project showed that the mean monthly rockfall activity (total volume of rock falling out of the face) is directly correlated to the size of the final failure. In addition, it can be seen that in the month before a significant failure, the total rockfall volume for that month increases significantly.

The reason for this correlation can be explained in geological terms. Rockfalls are caused by differential strain and deformation of the rock mass. This can coincide with the evolution of a brittle fracture. If a fracture starts to develop that daylights on the rock face, then the increasing stress at this point will cause rockfalls. As the fracture develops, the strain deformation at the rockfall will increase causing rockfalls. Eventually this increases exponentially, leading to larger rockfalls and subsequent failure of the rock face.

Currently, most monitoring and failure prediction in the mining industry is undertaken by radar systems that focus on the detecting small scale movements of the whole rock face. This is appropriate in some circumstances but the monitoring method should be decided by the geotechnical environment. Using rockfall as a predicitor may be more appropriate in some environments and this will be a useful tool for the geotechnical engineer.

Using SiteMonitor4D with the new Rockfall Analysis feature allows users to have a clear view of the stability and changes of mass within a slope, allowing the user to plot the monthly rockfall activity against time. This advanced visibility allows users to take action before a critical situation occurs.

3D Laser Mapping, www.3dlasermapping.com

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