Friction stabilizers for rock bursts hazard mitigation in deep mines’ environments

Abstract

As underground mining reaches deeper and deeper deposits of useful materials, it is associated with an increasing threat from rock outbursts, which have become the greatest challenge in securing the excavations with appropriate ground support system. Also, despite decades of research, effective management of rock burst still continues to be a formidable challenge in underground operations. Therefore, selecting and designing the most suitable support systems are crucial for securing underground openings, limiting their deformation and ensuring their long-term stability. In a such situation, energy absorbing rock bolt is today recognized as an important support element in deep mines around the world. Ground support system composed on energy absorbing elements is able to utilize the general principle of ground control in rock burst prone conditions. This consists in the dynamic energy transfer on the yielding support system to facilitate absorption and controlled deformation of rock mass.

The paper shows that in the case where stiff rock bolts cannot provide stability of excavation walls (i.e., the load is much higher than the bolt’s capacity), energy-absorbing yield ground support can successfully confine or even eliminate the risk of failure by allowing controlled movement of the expelled blocks of rock. The developed 2-dimensional model of rock bursts from an underground excavation’s sidewalls, based on the LEM (Limit Equilibrium Method), is relatively simple and sufficiently general analytical approach for formulating practical conclusions and recommendations with respect to selecting the best methods of ground support, particularly in the geological and mining conditions of deep mines. Presented herein model may be applied to continuous types of rocks as well as to rock mass characterized by more than one joint/discontinuity system. Also, the rock heterogeneity within sidewalls does not disturb the theoretical background of the developed models however it does require an additional analytical work to be done. The main contribution of this paper is the development of an algorithm for quantitatively tracking rock burst phenomena as a function of time (acceleration, velocity, and displacement of expelled rocks) as well as indicating the required ground support reinforcement. The advantages of the method are demonstrated using two types of energy-absorbing yield rock bolts: Split Sets and the new CTw twisted rock bolts. It is accepted that the so-called critical depth, at which the force unbalance can overcome the rock’s mass resistance, is the most important reference parameter for indication a rock burst high potential. The critical depth value under actual mining/geological conditions may be determined based on the obtained diagrams, not attached to the paper.