Por: Ricardo Berrocal Mallqui, Geomecánica Andina.

Presentado en el 8° Simposio Peruano de Geoingeniería.

Resumen

Rockbursts originate as a dynamic process developed by structural impacts that cause seismic events (waves) and by the redistribution of stresses around excavations associated with the elastic deformation of the rock, which is then converted into kinetic energy. It should be noted that unused energy is released in the displacement (or bulging) and subsequently generates the expulsion of the rock mass.

The fractures manifest progressively, reaching a critical extensional deformation that generates lateral deformation, a stage in which sufficient energy accumulates, fluctuating between 0.4 and 0.6 of the initial maximum resistance. The stresses applied are not only due to the position (direction of forces) of the brittle burst (spalling) but also to the depth of the burst of the wall or excavation face, expressed by the ratio of the average compressive strength (σmax) caused by the tangential stress and the compressive strength of the rock (σci).

Therefore, to keep the excavation stable, support systems have been designed considering their capacity to absorb dynamic energy before rock expulsion or bursting occurs.

The phenomenon of rockburst causes accidents every year in deep mines and tunnels as a result of the deformation and violent ejection of volumes of rock due to the formation of rock spalling, which can be several decimeters thick depending on the mechanism and intensity of the surrounding medium.

In deep excavations, this released energy can cause damage to underground works, posing danger to people and machinery and leading to downtime, economic losses, etc., depending on the depth reached, the volume of rock ejected, the magnitude of the stress, the scope of the seismic event, and its proximity to the excavations.