Ground Control Methods in High-Stress Ground Conditions in Civil and Mining Tunnels- Case Studies, and Benchmarking

Abstract

Extreme ground behavior in high-stress rock masses such as rockburst prone and squeezing ground conditions are encountered in a range of underground projects both in civil and mining applications. Determining the most appropriate support system in such grounds is one of the major challenges for ground control engineers because there are many contributing factors to be considered, such as the rock mass parameters, the stress condition, the type and performance of the support systems, the condition of major geological structures and the size and geometry of the underground excavation. The main characteristics and support requirements of rockburst-prone and squeezing ground conditions are critically reviewed and characteristics of support functions are discussed. Different types of energy-absorbing rock bolts and other internal and external support elements applicable for ground support in rockburst-prone and squeezing grounds are introduced. Important differences in the choice and economics of ground support strategies in high-stress ground conditions between civil tunnels and mining excavations are discussed. Ground support benchmarking data and mitigation measures for mines and civil tunnels in burst-prone and squeezing grounds conditions are briefly presented by some examples in practice. The importance of the application of shotcrete shells with yielding elements in squeezing ground conditions has been presented in detail by a simplified Convergence Confinement Method (CCM) example.