Evaluation system of remedial works for long-term stability of tunnels due to deterioration of surrounding ground

本研究基于应变硬化-应变软化弹粘塑性模型，采用有限元方法研究了闭区隧道的长期稳定性。本文的研究目的是探讨隧道围岩随时间变化而引起的隧道长期稳定的机理。特别注意的是由于应变软化和土壤的时间依赖行为引起的应力在地下的重新分布。在此基础上，提出了一种评估隧道长期稳定性和隧道修复效果的新方法。研究发现，由于地基的时变特性，作用在隧道衬砌上的土压力是不断变化的。还发现，洞洞的存在可能会极大地改变弯矩的分布，并可能导致混凝土开裂。对存在的洞室进行注浆和锚杆的修补工作，对降低衬砌截面力是非常有效的。将计算结果与长期积累的现场实测结果进行了比较和校核。数值分析表明，本文提出的数值分析评价方法能够较好地模拟隧道长期稳定机理和修复工程效果，可应用于现场工程。

In this research, based on elasto-viscoplastic model with strain hardening and strain softening, finite element analyses were conducted to investigate the long-tem stability of tunnel in shuttered zone. The purpose of the research is to investigate the mechanism of the long-tem stability of the tunnel due to the time dependent behavior of surrounding ground. Particular attention has been paid to the redistribution of the stress within the ground due to the strain softening and the time dependent behaviors of soils. From the analysis, a new approach for assessing the long-term stability of tunnel and the effectiveness of the remedial work carried out for the tunnel was proposed. It is found that due to the time dependent behavior of the ground, the earth pressure acting on the tunnel lining changes constantly. It is also found that the existence of a cave may greatly change the distribution of the moment and may lead to the cracking of concrete. The remedial work, that is, the injection of mortar into existed cave, and rock bolts are found to be very effective in reducing the section force of lining. The calculated results are compared and checked with the results obtained from field measurements accumulated in a long period. It is found from the numerical analysis that the evaluating method using the numerical analysis proposed in this research is capable of simulating the mechanism of long-term stability of tunnel and the effectiveness of the remedial works to a reasonable accuracy and can be applied to field project.