Research on the Calculation Method of Vertical Load Acting on Tunnels in Inhomogeneous Strata

When the tunnel passes through inhomogeneous strata, due to the sharp difference in the physical and mechanical properties between different strata, the vertical load acting on tunnels calculated by the classic Terzaghi theory deviates significantly from the real situation. Based on the classic Terzaghi theory, the paper proposes a new calculation method of vertical load acting on tunnels in inhomogeneous strata by assuming the sliding plane as poly straight lines. Considering five tunnel-crossing scenarios, the calculation formulae of vertical load are derived for the case when the soft layer is above the tunnel and the case when the tunnel passes through the soft layer, respectively. The proposed model is validated by comparing with the earth pressures measured in the Zhuhai Tunnel and Shiziyang Tunnel projects. The variational law of vertical load acting on tunnels in inhomogeneous strata with the key parameters of soft layer is obtained through parametric studies on the internal friction angle, thickness and position relative to tunnel of the soft layer and by comparing with the calculation results of the classic Terzaghi model and the straight sliding plane model.