Rockburst means stress-induced loosening of rock mass in tunneling and mining. Rock masses come off under high energy release. To determine this energy, different approaches exist, depending on different countries and regions.
Rockburst phenomena mostly occur in deep tunnels and mines but also in regions where high horizontal stresses appear. Loosening of the overburden also depends on the shape of the tunnel or mine excavation. Circular excavations are preferable as rough edges increase stress and can lead to overburden collapse.
The development of an adequate retaining system, such as dynamic anchors together with high-tensile steel wire mesh and their behaviour during rockburst has been tested and quantified.
The evaluation and description of the interaction of anchors and meshes in case of rockburst has been investigated. Using this new test setup it is now possible to test the interaction between the anchors and the steel wire mesh and to show how much energy will be absorbed by the anchors, mesh and the system itself. To simulate the rockburst failure, Geobrugg engineers considered a concrete slab which is hidden by a rock and will burst into the anchored protection net.
The dynamic reaction of anchors and mesh with the failure is measured with load cells, acceleration sensors and high-speed cameras. These findings will result in a complete dimensioning concept for rockburst protection systems in underground mining.
The installation of the mesh and anchors will still be carried out fully mechanised by the operator of the underground Jumbo or bolter. The TECCO mesh, supplied in rolls, reaches over the entire drive size and advance length, and is unrolled and bolted onto the wall by the jumbo operator in one working process. Due to the all-in-one-step process, installation times can be reduced by up to 40%.
Image: Fully mechanised installation of the TECCO mesh with the MESHA installation handler.