Lower bound stability analysis of plane strain headings in Hoek-Brown rock masses

Abstract

Tunnel face stability is an important issue for the safety assessment of tunneling constructions. In this paper, the lower bound (LB) finite element limit analysis in conjunction with semidefinite programming (SDP) is developed and employed to investigate the stability of plane strain tunnel headings in Hoek-Brown (HB) rock masses. Lower bound solutions of the load factor of the problem for the practical ranges of dimensionless parameters are extensively examined including the cover-depth ratio of headings, the normalized uniaxial compressive strength of intact rock, the Geological Strength Index (GSI), and the HB material constant (mi). The failure mechanisms associated with those parameters are discussed and compared. The safety assessment of relatively long-wall tunnels or mining in rock masses can be reliably and accurately performed by employing the presented results in practice.