基于贝叶斯网络的盾构隧道结构易损性评价方法研究

The performance deterioration of shield tunnel has been the grand challenge for engineering. The performance deterioration over the lifespan of bridges has been extensively studied. However, it has been rarely investigated for shield tunnels because the unique operational envioroment makes the development of tunnel performance more complex than bridges. Due to the lack of the deterioration models of tunnel lifetime performance, tunnel maintenance (including inspection and repair) is often empirically designed, which can be either under- or over-designed. Under-design tends to quicken performance deterioration and tunnel distress, while over-design is cost-inefficient and must be avoided given limited resources. The objectives of this research are to: (1) obtain the development of shield tunnel bahavior under complex operational envioroment; (2) transform the ultimate limit state into shield tunnel assessment and maintenance capacity ; and (3) develop Bayesian Network- based vulnerability assessment model for shield tunnels. In this research, we firstly propose the non-linear calculation model for tunnel joint to study the tunnel response to the complex operational enviroment, namely, ground conditions and surcharge et al. Then the model tests and refinement numerical simulation are performed to verify the calculation model. Based on the tunnel performance and tunnel safety, the ultimate limit state of the shield tunnel is presented. Consequently, the failure patterns based on the tunnel performance and safety is proposed. The progressive deterioration of shield tunnel could be obtained. The ultimate limit state is then transformed into the tunnel assessment. Bayesian networks is then adopted to develop the vulnerability assessment model of shield tunnel, which contains the shield tunnel vulnerability evaluation index, soil parameters and trigger index, such as gound surface surcharge. Learning cases is used for bayesian network to get the conditional probability. The bayesian network can be updated automatically with field data. The state of the shield tunnel can be assessed, predicted and updated with the proposed assessement method. It is expected to be much helpful to restore and improve the deteriorating tunnels.

随着运营盾构隧道结构性能不断劣化，合理评价盾构隧道结构状态成为保证隧道服役性能及结构安全迫切需要解决的问题。然而由于盾构隧道纵向里程较长，地层条件、环境变化、拼装方式的差异等使隧道结构表现出不同的抗力和结构响应特性，隧道结构的损伤程度、规律及其对系统安全的影响亦不同，然而目前的隧道结构评价中忽略了这些差异，无法对盾构隧道结构性态进行合理的评价，使得对盾构隧道的维护只能依据经验进行。本项目基于土层性质和环境变化的差异，利用理论模型揭示盾构隧道结构性态发展规律和特点；基于盾构隧道功能和结构安全要求，建立盾构隧道结构极限状态功能函数；提出盾构隧道功能和结构失效模式；揭示盾构隧道结构性态渐进性发展规律及失效特点；提出盾构隧道结构评价基准；建立基于贝叶斯网络的盾构隧道易损性评价模型，形成盾构隧道结构分析、评价和预测方法；基于工程实践实现盾构隧道结构评价方法的优化，为运营盾构隧道结构维护提供依据。

随着盾构隧道运营时间的增加，结构病害不断出现，给隧道服役性能和结构安全带来了严峻挑战，揭示隧道结构安全性态发展规律、合理评价盾构隧道结构状态成为保障隧道结构安全的核心问题。然而，由于影响隧道结构安全的原因复杂且对隧道结构产生耦合作用，使得隧道结构性态演化机理复杂，结构病害原因难以诊断，隧道结构安全状态难以合理评价。因此，本项目采用足尺模型试验、理论解析和数值模拟方法，建立了振动和渗漏耦合作用下的隧道结构性态演化分析方法，提出了基于管片安全和接头安全的承载力功能函数，建立了隧道结构易损性评价及病害原因诊断模型，提出了隧道结构安全动态评价方法。研究成果对保障运营盾构隧道结构安全提供了技术支撑。. 研究内容和成果如下：（1）基于列车-轨道-隧道-地基解析模型，建立了地铁振动荷载确定方法，在此基础上，考虑隧道渗漏影响，通过大循环次数下弹塑性水土耦合动力有限元计算，揭示了振动荷载和渗漏耦合作用下盾构隧道纵、横向长期性态变化规律；（2）进行了足尺的管片接头试验，采用理论分析与模型试验相结合的方法，揭示了接头性能演化规律与易损性特征，提出了基于接头防水安全的接头承载力安全系数Kc，为盾构隧道结构易损性评价提供了新方法；（3）提出了盾构隧道接头解析模型，建立了盾构隧道易损性评价模型，考虑隧道结构性态演化规律，提出了基于盾构隧道横向收敛变形和接头张开量变形作为隧道易损性评价指标；（4）利用隧道结构易损性评价模型，考虑隧道结构影响因素条件更新，实现了盾构隧道结构易损性预测和损伤原因诊断；（5）基于隧道结构性态演化规律和易损性发展规律, 考虑隧道病害等级和相关性的影响，建立了隧道结构安全状态动态评价方法，实现了隧道结构多层次结构安全评价方法。