非关联流动特性下盾构隧道失稳地层塑性流动机制及地表沉陷预测研究

The ground collapse, which is induced by shield tunnel construction in urban area, has the characteristics of randomness, unpredictability and high-harmfulness. Due to the complexity of exterior loads, the diversity of tunnel dimensions, and the variety of soil mediums, the cognition of the plastic flow mechanism caused by shield tunnel instability was significantly restricted. Based on upper-bound theorem of plasticity, a plastic-dissipation-based mesh adaptive algorithm will be first introduced into the upper-bound finite element method, and the energy dissipation model for analyzing shield tunnel stability is established with respect to the non-associated flow rule of the geotechnical material. The characteristics of plastic flow deformation of the geotechnical material and evolution laws of soil sliding locus are determined under coupling action of multiple loads. Then the upper-bound rigid-block mechanisms for shield tunnels are modified according to the optimal collapse mechanisms. Moreover, a relationship between the velocity field and displacement field in the critical state is built, and a further development will be carried out to reveal the evolution laws of the surface subsidence curve and distribution characteristics of main failure region. Then a framework, which is influenced by factors such as stratum condition, tunnel dimension and exterior load, will be proposed for predicting the critical surface subsidence. Furthermore, numerical simulation and model test will be carried out to verify the theoretical results. This project will broaden system of the geotechnical plastic theory, and it is of great theoretical significance in improving risk analysis technique and risk control during the construction of shield tunnel in urban area.

城市盾构隧道施工引发的地层塌陷破坏具有随机性、不可预料性和高危害性等特征，由于外部荷载的复杂性、隧道尺寸的多样性以及所处介质的多变性，对城市盾构隧道失稳引起的地层塑性流动机制的认识存在较大的局限性。本项目首先将以耗散能为单元加密判据的自适应加密算法引入极限分析上限有限元法，构建考虑岩土体非关联流动特性的盾构隧道稳定性自适应上限有限元能耗分析模型，揭示多种荷载耦合效应下隧道失稳地层塑性流动变形特征及土层滑动轨迹演变规律，修正刚性滑块上限法假定的破坏模式；在此基础上，构建极限状态地层塑流场与稳态位移场间的关联关系，研究地表塑性流动特性曲线演变规律及地表沉陷关键区域分布特征，形成与地层条件、隧道尺寸及荷载等相关的临界地表沉陷非线性预测方法；同步开展数值仿真和模型试验，对比效验理论分析结果。项目研究可以完善岩土塑性理论体系，对于提高我国城市盾构隧道施工风险分析和控制水平具有重要的理论指导意义。

城市盾构隧道施工引发的地层塌陷破坏具有随机性、不可预料性和高危害性等特征，由于外部荷载的复杂性、隧道尺寸的多样性以及所处介质的多变性，对城市盾构隧道失稳引起的地层塑性流动机制的认识存在较大的局限性。本项目首先将以耗散能为单元加密判据的自适应加密算法引入极限分析上限有限元法，构建考虑岩土体非关联流动特性的盾构隧道稳定性自适应上限有限元能耗分析模型，揭示多种荷载耦合效应下隧道失稳地层塑性流动变形特征及土层滑动轨迹演变规律，提出刚性滑块上限法假定的破坏模式；在此基础上，构建极限状态地层塑流场与稳态位移场间的关联关系，研究地表塑性流动特性曲线演变规律及地表沉陷关键区域分布特征，形成与地层条件、隧道尺寸及荷载等相关的临界地表沉陷非线性预测方法；同步开展数值仿真研究，对比效验理论分析结果。项目研究可以完善岩土塑性理论体系，对于提高我国城市盾构隧道施工风险分析和控制水平具有重要的理论指导意义。本项目研究取得了较好的研究进展，在国内外期刊上发表学术论文8篇（SCI收录论文6篇），授权发明专利2项、实用新型专利4项，获省部级科技进步二等奖2项。