深部软弱地层TBM掘进围岩挤压变形卡机机理及分析预测方法

Squeezing deformation will be produced easily when TBM advances through deep soft ground with high in-situ stress, which may exceed the overcut between the surrounding rock and the shield, and then contact and extrude the shield, leading to shield jamming while the thrust supplied by the propulsion system is not sufficient to overcome the friction on the shield. The Mechanism and simulation analysis method of squeezing deformation and its induced shield jamming is the key and difficult points of this program. This study focuses on the key scientific problem of ‘mechanism, continuous-discontinuous model and simulation analysis method for damage-dilatancy and fracture-bulking squeezing deformation’, combining with the research methods of experimental study, theoretical analysis, numerical simulation and field test, the mechanism of squeezing deformation under TBM excavation unloading will be revealed, and the corresponding mechanical model for damage-dilatancy and rupture-bulking squeezing deformation process will be established; then, based on the theory of Convergence-Constraint Method, by studying on the interaction mechanism between surrounding rock and shield, the mechanism of shield jamming will be revealed, and forecast analysis models of shield jamming are set up, which includes mechanical model of the generation process and criterion of shield jamming; finally, upon on the above results, the simulation analysis method of squeezing deformation and shield jamming process will be put forward based on the Combined Finite-Discrete Element Method (FDEM). The research results would provide theoretical support for prediction and analysis of squeezing deformation and the induced shield jamming disaster.

TBM穿越深部高地应力软弱地层时围岩易产生挤压变形，当其变形量超过扩挖预留的围岩与护盾间变形间隙，围岩接触并挤压护盾，对护盾产生的摩阻力超过推进系统推力时将导致护盾被卡。其中，挤压变形卡机的孕育发生机理及分析预测方法是研究的重点和难点。本项目围绕关键科学问题“围岩损伤扩容-破裂碎胀挤压变形机理、连续-非连续力学模型和分析模拟方法”，采用室内试验、理论分析、数值模拟和现场监测相结合的研究方法，揭示TBM掘进卸荷条件下挤压变形机理，建立描述围岩损伤扩容-破裂碎胀挤压变形过程的力学模型；其次，基于收敛约束法研究护盾区挤压变形时空演化规律及其与护盾相互作用机制，揭示卡机孕育发生机理，建立卡机分析预测模型（卡机孕育过程力学模型和卡机判别准则）；在此基础上，基于有限元-离散元耦合分析方法(FDEM)，提出挤压变形与卡机过程模拟分析方法，为TBM掘进挤压变形与卡机灾害分析预测提供理论支撑。

TBM穿越深部高地应力软弱地层时围岩易产生挤压变形，当其变形量超过扩挖预留的围岩与护盾间变形间隙，围岩接触并挤压护盾，对护盾产生的摩阻力超过推进系统推力时将导致护盾被卡。其中，挤压变形卡机的孕育发生机理及分析预测方法是研究的重点和难点。本项目围绕关键科学问题“围岩损伤扩容-破裂碎胀挤压变形机理、连续-非连续力学模型和分析模拟方法”，采用室内试验、理论分析、数值模拟和现场监测相结合的研究方法，首先开展了反映TBM开挖卸荷特征的砂质泥岩三轴卸围压试验和三轴卸荷蠕变试验，分析了卸荷和蠕变过程中的软岩损伤、变形、破坏规律，揭示了挤压变形机理，即深部软弱围岩挤压变形由TBM开挖卸荷产生的峰前损伤扩容和峰后破裂碎胀引起。考虑了掌子面空间效应和围岩粘性时效特性，研究了护盾区域围岩挤压变形的时空演化规律及其对护盾接触-挤压-摩擦相互作用过程的控制作用，揭示了TBM卡机灾害的孕育发生机理：护盾区域围岩挤压变形时空效应显著，护盾区域围岩挤压变形随着与开挖面距离增大而增大，在某一点处其径向位移达到扩挖预留变形间隙，从这一点开始围岩与护盾接触并挤压护盾，进而在TBM推进时，围岩对护盾产生摩擦阻力，当TBM前移时推进系统所提供的推力不足以克服护盾所受的摩阻力时，便发生TBM卡机。并据此建立了挤压变形卡机灾害孕育致灾过程力学模型，提出了卡机灾害判别准则。将质量阻尼、准静态摩擦和损伤卸荷强度准则引入到FDEM计算方法中，改进了接触对的检索方式，实现了TBM掘进围岩破裂碎胀挤压变形和卡机过程的模拟，形成了挤压变形卡机孕育发展模拟预测的FDEM方法。项目以新疆ABH输水隧洞为依托工程，开展了挤压变形卡机灾害预测分析研究，研究成果在依托工程得到了应用和验证。本项目揭示的挤压变形卡机灾害致灾机理和提出的挤压变形卡机FDEM分析预测方法对挤压变形卡机灾害的预测和控制具有重要指导意义。