Ground Support for Extreme Conditions

Abstract

Ground support is routinely employed to maintain the structural integrity of excavations in rock. In extreme conditions, such as observed in seismically active mines and in excavations in squeezing rock this can be challenging. In seismic conditions, ground support is required to prevent excessive levels of rock mass dilation, sustain confinement around the reinforcement and absorb kinetic energy released through the process of brittle rock mass failure and ejection. This is only possible if the ground support works as an integrated system to maintain the load distribution between all elements. In extreme squeezing ground the role of support is to maintain access for the working life of the excavations. Recent years have seen the development of yielding or energy absorbing reinforcement and surface support elements that can perform better than conventional support in extreme conditions. An improved understanding of the loading mechanisms and better data on the capacity of ground support complemented by field observations have resulted in improved ground support practice for extreme conditions. The long-term performance of ground support can be hindered when exposed to corrosive environments. In extreme corrosive environments ground support is susceptible to degradation that may severely reduce its capacity to meet its performance goals for the intended service life of the excavations. This requires protective processes to prolong the service life of ground support or to plan for rehabilitation when a reduction in capacity is deemed critical. This paper reviews recent developments in ground support strategies for extreme conditions, including mine seismicity, squeezing environment and corrosive environments. In this context the role and timing of rehabilitation of ground support can have significant safety and economic implications.