浅埋隧道开挖面破坏机理的非线性能耗分析方法与试验研究

The surface subsidence accidents caused by instability of the front of a tunnel driven in shallow strata occur frequently, which will threaten to people's life and property. However, the linear failure criterion commonly used in face stability analysis of shallow tunnel is hard to reflect the nonlinear failure characteristics of soil. Thus, the failure mechanism of a shallow tunnel face is investigated on the basis of the nonlinear failure characteristics of soil in this study. By constructing an upper bound failure mechanism, the nonlinear energy consuming model of shallow tunnel face was established and the supporting pressure and failure mode of shallow tunnel face at critical state were obtained. Furthermore, the failure mechanism of tunnel face at limit state and the influence of soil nonlinear parameters on tunnel face stability were revealed. To evaluate the validity of the theoretical analysis, the results of theoretical analysis were compared with the numerical simulation and centrifugal model experiment results. Combining the theoretical calculation and centrifugal model experiment, the failure characteristic and failure mechanism of shallow tunnel face were studied, which provided theoretical foundation for stability evaluation and supporting structure optimization design of shallow tunnel in practical engineering.

我国的城市地下铁道在修建过程中经常出现由于开挖面失稳造成的地表塌陷事故，给人民群众的生命和财产安全带来极大的隐患。目前浅埋隧道开挖面稳定性分析中常用的线性破坏准则难以准确反映土体的非线性破坏特性，针对这一现状，本课题根据土体的非线性破坏特性对浅埋隧道开挖面的失稳机理展开了研究。通过构建浅埋隧道开挖面上限破坏机制，建立浅埋隧道开挖面的非线性能耗模型，得到浅埋隧道开挖面在临界状态下的支护力和破坏模式。分析开挖面的破坏特征，揭示极限状态下开挖面失稳发生机理和土体非线性参数对开挖面稳定性的影响规律，并利用数值模拟和离心模型试验对理论分析结果的有效性进行验证。本课题结合理论计算和模型试验对浅埋隧道开挖面破坏模式和失稳机理进行研究，为实际工程中浅埋隧道稳定性评估和支护结构优化设计提供了理论依据。

本课题采用极限分析上限定理和变分理论，结合数值模拟技术对隧道开挖面和围岩塌落破坏机理以及非线性失稳特性开展研究，完成了预期研究目标，取得了预期的研究成果。主要研究成果如下：. (1) 基于空间离散技术，构建了一种适用于复杂环境的盾构隧道开挖面破坏机制，通过将各种影响因素引入上限计算，得到了复杂因素作用下盾构隧道开挖面的极限支护力和破坏模式。.(2) 提出了基于上限理论的隧道开挖面稳定性分析方法，计算了可以用于定量评估隧道开挖面稳定性的安全系数，为隧道开挖面稳定性分析提了供理论依据。.(3) 利用已有的三维多块体破坏机制，采用切线法将非线性破坏准则引入了上限计算，得到了非线性破坏准则下的盾构隧道开挖面安全系数上限解。.(4) 开发了基于非线性Mohr-Coulomb破坏准则的自定义本构模型，将该本构模型嵌入到有效差分软件FLAC中，实现了非线性Mohr-Coulomb本构模型在数值模拟过程中的即时调用，并通过算例验证了该自定义本构模型的有效性。.(5) 构建了隧道底部存在隐伏溶洞的隧道围岩上限破坏机制，提出了基于变分理论的隧道围岩塌落面上限解计算方法，利用该方法计算得到了隧道围岩塌落面方程解析解，揭示了隧道围岩非线性破坏机理的初步规律。.(6) 在课题执行期内发表学术论文16篇，其中SCI/EI收录论文7篇（其中录用待刊2篇），CSCD源刊论文3篇；另外，还有两篇论文正在外审中。