Evaluation of ground management in underground excavation design

摘要

A variety of challenges and problems are encountered by unstable rock failure which is associated with in situ stress, geological structures, geometry, excavation sequence, groundwater and operational conditions. It is basically required predicting ground behaviour and rock failure mechanism in a modern design of underground excavations. The complexity of ground conditions and uncertainties make it more difficult to control and avoid occurrences of failure. Ground management is a process to predict rock mass behaviour and failure modes, and apply proper ground support systems. Hazard identification and failure mechanism assessments assist in selecting suitable design method(s) to manage risks. The aim of this paper is to consider the main types of rock structure and rock mass behaviour modes to outline ground management in underground excavation design. Evaluation of rock mass instability conditions by proper design methods can provide a safe environment in working stopes. The Karari underground gold mine has been used as a case study. The rock mass structure was characterised as jointed/blocky/bedded class and ground behaviour types identified for evaluation were 'intact rock failure', 'structural failure' and 'water effect'. The primary planning for ground management established to evaluate rockbolts, mesh and shotcrete as a ground support system, and using smooth blasting/sequential excavation method in faults and shear zones to control possible failures in the portal access of the mine.