A Hybrid Methodology of Rock Support Design for Poor Ground Conditions in Hard Rock Tunnelling

Abstract The design of rock support in hard tunnelling is often assisted by the use empirical engineering mass classification systems. This has involved a wide variety geological- and mechanical-conditions, including poor ground conditions like fault zones weak rocks. For most encountered situations, designs have performed well. However, systems pose several limitations to describe behavior derive optimal as discussed publications during last decades. In present study, an analysis 118 case records, mostly from monitored Norwegian tunnel sites, been undertaken investigate performance current practice with Q-system when exposed conditions. results revealed significant improvement possibilities which relate Among others, rocks, anisotropic rock, transition self-bearing masses requiring load-bearing tunnel, typically quality Q < 1. As result, set improvements recommendations developed integrated or hybrid methodology specific for proposed. approach combines main components advantages different methodologies provides guidance optimization where presents limitations.