砂卵石地层盾构隧道掌子面稳定性理论分析

Study on Face Stability of Shield Tunnel in Sandy Cobble Stratum

摘要:

盾构隧道穿越砂卵石地层掘进施工时，由于砂卵石的地层特性及施工扰动，隧道掌子面容易失稳而引发事故。为研究砂卵石地层盾构隧道掌子面稳定所需的最小支护力，结合砂卵石地层的掌子面失稳模式，在三维Murayama模型的基础上，将掌子面前方土体的滑动面形式假设为对数螺旋滑移线，结合上部松动区域的破坏机制，引入椭球体放矿理论，对传统的棱柱体筒仓模型进行改进，进一步通过极限平衡法推导出砂卵石地层的掌子面极限支护力求解公式；最后通过离散元数值模拟验证所推公式，两者的误差为3.1 %。结果表明所得公式可对砂卵石地层的掌子面极限支护力进行较为精确的求解。研究成果以期为砂卵石地层掌子面极限支护力计算理论提供依据。

Abstract:

When the shield tunnel passes through the sandy cobble stratum， it is easy for the tunnel face to lose stability and cause accidents due to the stratum characteristics and construction disturbance of sandy pebble. In order to study the minimum supporting force required for the stability of the shield tunnel face in sandy cobble stratum， in combination with the instability mode of the tunnel face in sandy cobble stratum， and based on the three-dimensional Murayama model， the sliding surface of the soil in front of the tunnel face is assumed to be a logarithmic spiral slip line. In combination with the failure mechanism of the upper loose area， the ellipsoid drawing theory is introduced to improve the traditional prism silo model， and the limit support of the tunnel face in sandy cobble stratum is further derived by using the limit equilibrium method. Finally， the formula is verified by discrete element numerical simulation， and the error between the two is 3.1 %. The results show that the formula can accurately solve the limit support force of the tunnel face in sandy cobble stratum. The research results are expected to provide new ideas for the calculation of limit supporting force of tunnel face in sandy cobble stratum.