Stability of rectangular tunnel in Hoek–Brown rocks under steady-state groundwater flow

This research study aims to determine the stability of a rectangular tunnel excavated in rock masses obeying Hoek–Brown yield criteria under steady-state groundwater flow using lower bound limit analysis. During tunnelling in the presence of groundwater table (GWT) seepage forces are generated, which causes a decrease in the stability of rock mass. The total head distribution due to seepage is obtained by using two-dimensional finite element software Optum G2. The stability has been presented by a non-dimensional number σ_ci/γ′_maxH obtained for various combinations of B/h, H/h, H_w/h, σ_ci/γ_wh, m_i, GSI and D where B and h are width and height of the tunnel, respectively, H is the depth of the tunnel from the ground surface and H_w is the height of GWT from the tunnel roof, respectively, σ_ci and γ′ are uniaxial compressive strength and submerged unit weight of rock, respectively, γ_w is the unit weight of water and m_i, GSI and D are the Hoek–Brown parameters.