SiteMapper 4D Rockfall Analysis
3D Laser Mapping Systems’ SiteMonitor is a “high accuracy, long range monitoring solution” for rock faces. It was designed in 2004 to alert mine safety managers by text message or email when problems arise. Now it can also predict the failure of a rock wall ahead of time.
The system’s new Rockfall Analysis feature “allows you to have a clear view of the stability and changes of mass within a slope, allowing you to plot the monthly rockfall activity against time. This advanced visibility allows you to take action before a critical situation, allowing for increased safety.”
The system gathers data using a laser scanner to measure each 144mm grid of the rock face every 30 minutes. According to 3DLM, this enables monitoring of small rock falls and geological structures at an accuracy that other methods won’t allow. 3DLM claims that the smallest detectable rockfall is 0.00001 cubic meters of rock.
3D Laser Mapping developed their Rockfall Analysis technology partly through a research project with Durham University that saw them collecting and analyzing laser scan data for 100,000 square meters of coastal cliffs over the course of eight years.
As 3D Laser Mapping explains, “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.”