Affiliation:
1. Technical University of Crete
Abstract
The stability analysis of underground excavations is a crucial part of the design of underground excavations. One of the most common collapse hazards derives from rock mass cracking which creates potential wedge blocks falling or sliding into the tunnel. Many researchers have addressed this subject and are trying to resolve this critical issue for the safety of underground tunnels. The most extensive research involves implementing finite or discrete element numerical algorithms to analyze wedges. However, this analysis is time-consuming; alternative short stability assessment techniques are based on classification systems (e.g., GSI, RMR, Q etc.). Another widespread technique is block-theory, which kinematically considers the possibility of overhanging block collapse into the tunnel. These blocks' safety factor (SF) calculation is analyzed by performing several techniques. The most known is the calculation of pull-out force and stress relaxation, as well as the technique of shear strength analysis also used in Rocscience's Unwedge program. In this paper, the SF calculation techniques are reviewed and compared. An alternative methodology of calculating SF is proposed to extend their application to non-symmetric and polyhedral wedges.
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