盾构隧道开挖面支护力上限分析

盾构在掘进的过程中,必须确保隧道开挖面前方土体的稳定。将隧道沿纵向简化成平面应变情况,利用双对数螺旋线破坏模式,基于极限分析上限定理,对隧道开挖面前方土体的主动破坏形式进行研究。将盾构机作用在开挖面上的支护力视为均布荷载,得到支护力的上限解,利用Matlab软件编程求解该上限解的最优解,讨论各参数对破坏模式形状和支护力大小的影响。研究结果表明：破坏模式的形状由内摩擦角φ决定;随着黏聚力c和内摩擦角φ的增大,隧道的支护反力σt减小。

Upper bound analysis of supporting pressure for shield tunnel faces

The stability of the soil in front of the tunnel excavation face should be guaranteed in the process of shield excavation. Simplifying the tunnels into plane strain condition in the longitudinal direction and using failure mechanism of double logarithmic spiral,the active soil failure mechanism in front of the tunnel excavation face was investigated based on upper bound theorem of limit analysis. The upper solutions of supporting forces were obtained by taking the supporting forces acting on the excavation face by shield machine as uniformly distributed loads. A Matlab program was established to obtain the optimal result of the upper bound solutions. The influences of the various parameters on both the value of the supporting forces and the shape of the failure mechanism were discussed at the end of this paper. The results show that the shape of the failure mechanism is determined by internal friction angle φ. With the increase of cohesive force c and internal friction angle φ,the supporting forces σt tend to decrease.