Comparative Study of Rock Support System Design Practice for Large-Scale Underground Excavations

ABSTRACT: Rock support system design practices for large-scale underground excavations in North America, Europe, Japan and some other countries are reviewed in a systematic manner for about 110 case histories. Different rock support system design methods are summarized and data related to support quantities, such as arch concrete thickness, shotcrete thickness, rockbolt and anchor length, support pressure for the surveyed large-scale caverns are presented. Special attention is being paid to the comparison of engineering practices in Japan and other countries. Data re-analysis using Finite Element Method was performed for 37 cases to establish the anticipated depth of rock mass fracturing and to justify the adopted support pressure. It is found that support pressures applied to most caverns are reasonable and comparable based on the Q-index. It is also found that while reinforcement lengths for cavern sidewalls are generally acceptable, unnecessary long rockbolts or anchors have been applied to cavern roofs in many cases.