The 4th International Symposium on Mine Safety Science and Engineering (ISMSSE2018)

270 / 2018-04-15 04:04:05

Rock Support in Strainburst-prone Ground

brittle rock mass,support,strainburst,rockbolt,rock burst

Mine Dynamics Disaster > Rock burst impact

A rockburst is defined as damage to an excavation that occurs in a sudden and violent manner and is associated with a seismic event. Fault-slip burst, pillar burst and strainburst are three rockburst types that occur in underground excavations and constructions. In terms of damage to underground excavations, strainburst is the most frequently encountered. Strainbursts occur when the stress near an excavation reaches the peak strength of the rock mass and the rock mass fails suddenly in a violent manner. Strainbursts can be excavation- or mining-induced, seismically triggered by a remote seismic event or dynamically loaded by the related stress pulse. A detailed discussion on each type of strainburst triggering mechanism is presented first in this paper, followed by a discussion on the strainburst damage mechanisms.
To mitigate strainburst damage risk, effective rock support is needed. To design effective support systems for strainburst grounds, there is a need to understand four rock support functions: reinforce, contain, hold and connect. Reinforcing a rock mass strengthens the rock mass, controls the bulking process, and enables the rock mass to support itself. It will be illustrated that in strainburst-prone ground, it is critical to have rock support components to fulfill the role of rock reinforcement first. On the other hand, well-retained and reinforced rock masses may be excessively deformed and failed violently. In such a case, yielding elements are needed in the rock support system to absorb excessive strain energy released due to rock failure and tie the retaining elements and the reinforced broken rock to stable ground.
Conventional method to support strainburst-prone grounds is to install rock reinforcement system using rebar and mesh first and then install yielding support system using dynamic rockbolts at a later stage. This two-stage rock support installation process is not effective because it can adversely impact mine production schedule. In order to increase productivity without sacrificing safety, it is better to speed up rock support system installation and reduce cycle time. A new patented dynamic rockbolt is developed for rock support in burst-prone grounds. Laboratory testing confirmed that this new rockbolt has superb capacity to achieve the goal of reinforcing and holding rock masses. The new rockbolt is characterized by higher dynamic energy absorption capacity, consistent performance, and the ability to withstand repeated dynamic loadings. The new rockbolt can be used in a one-pass rock support system to facilitate rapid drift development in underground mines and increase mine safety.