有限元强度折减法在公路隧道中的应用探讨

将有限元强度折减法应用于隧道的稳定性评价。利用有限元强度折减法求得的安全系数与潜在滑动面，不仅可以评价隧道的稳定性和设计的合理性，还可以对支护参数和施工工艺提出改进建议。计算表明，泊松比? 的取值对塑性区范围影响很大，但对安全系数基本上没有影响；围岩等级越高，达到破坏状态时围岩的塑性区范围越大，破坏区却越小，安全系数越高；上覆岩体增厚，同类围岩塑性区范围和最大塑性应变值都增大，而安全系数减小。破坏时围岩等级高的隧道塑性区大，围岩等级低的反而小，因此，单纯根据塑性区范围大小来评判隧道的安全性是值得商榷的。

Application of strength reduction finite element method to road tunnels

Strength reduction finite element method is used in road tunnel. Based on latent slip surface and safety factor, the rationality of the designed parameters of support and excavations can be judged. The result shows that the distribution of plastic zone is effected greatly by Poisson’s ratios; however, safety factor varies little with it. The higher quality of rock, the more distribution of plastic zone under limit state is got. But the failure zone is lower. Additionally, the more thickness of upper rock layer, the more distribution of plastic zone under limit state is found. Meanwhile, the safety factor decreases. The example also shows that the plastic zone of good rock quality is larger than that of poor rock quality at failure condition. So it is deserved to study about judging safety of tunnel only by its plastic zone.