In response to the instability characteristics of the upper-soft and lower-hard strata,a stability calculation model for the tunnel face was proposed based on the hypothesis that the boundary between soft and hard strata caused by soil instability near the tunnel face first induced the formation of partial wedge-shaped bodies upward,and then developed into inverted conical shapes toward the ground.Firstly,the calculation model of partial wedge-shaped body was proposed through the limit equilibrium method.Subsequently,according to the modified calculation model of wedge-shaped body,the overlying soil pressure and the forces acting on the partial wedge-shaped body in front of the tunnel face were calculated respectively.Finally,relying on a tunnel section project of Qingdao Metro Line 6,numerical simulations were conducted to verify the theoretical model.The results showed that the soil deformation range under different conditions of supporting stress ratio was different,and the deformation mainly occurred in front of and above the tunnel face with the extension of bubble-like shape.The instability shape of tunnel face obtained from the numerical simulation basically accorded with the assumed shape of theoretical calculation model.The limit supporting stress ratio of the shield tunnel face obtained from the theoretical calculation was 0.21,with an error rate of 5％compared to the numerical simulation results.In addition,when the supporting stress of tunnel face was less than its limit value,the horizontal deformation of tunnel face in upper-soft and lower-hard strata would suddenly increase rapidly.The deformation of rock and soul near the tunnel face mainly occurred in the upper weak sections,and the maximum horizontal displacement appeared near the center of the upper-soft soil.There was a high relevance between the maximum horizontal displacement of soil on the tunnel face and the maximum vertical displacement of surface above it,both exhibiting similar deformation patterns.
关键词
盾构隧道/上软下硬地层/开挖面稳定性/极限平衡法/数值模拟
Key words
Shield tunnel/Upper-soft and lower-hard strata/Tunnel face stability/Limit equilibrium method/Numerical simulation
维普
万方数据