隧道围岩压力运动单元上限有限元计算方法

Rock pressures of tunnels based on finite element upper bound analysis method with rigid moving elements

针对隧道围岩压力与破坏模式问题,应用刚体平动运动单元上限有限元方法(UBFEM-RTME)与程序开展计算分析,获得了支护反力系数Nγ及Nc上限解曲线图和围岩有效间断线网破坏模式及其演变规律。与多种基于假定破坏机构的刚性块体上限法及模型实验结果进行对比分析,验证了UBFEM-RTME方法获得的支护反力σT上限解为极限分析上限理论框架内的较优解答,并且Nγ及Nc上限解与太沙基围岩压力解答变化趋势基本一致。除Nγ及Nc上限解外,UBFEM-RTME方法获得的隧道围岩有效间断线网破坏模式存在多种形态特征,大致涵盖了既有文献关于围岩破坏机构假定的多种型式,体现出该方法能摆脱假定破坏机构的限制,应用于隧道围岩压力求解具有良好适用性。

According to the determination of the rock pressures and collapse mechanisms of tunnels, the finite element upper-bound method with rigid translatory moving elements(UBFEM-RTME) is used to obtain the upper bound solution charts of the supporting force coefficients Nγ and Nc as well as collapse mechanisms with active discontinuities and evolution laws. Compared with a wide variety of the upper bound rigid block method(UBRB) assuming collapse mechanisms and the simulation model tests, it is verified that the upper limit solution of the support force obtained by the UBFEM-RTME method is the optimal solution in the theoretical framework of the upper bound limit analysis. At the same time, the upper bound solutions of Nγ and Nc are consistent with the trend of the rock pressure solutions of the Terzaghi theory. In addition to the upper solutions of Nγ and Nc, the UBFEM-RTME method has many morphological features in the collapse mechanisms with active discontinuities, and basically covers different types of failure mechanisms in the existing literatures. It is shown that the UBFEM-RTME method can get rid of the limitation of the assumed collapse mechanisms and has great applicability and superiority for solving the rock pressures of the tunnels.