富含大粒径漂石地层盾构刀具冲击破岩机理研究

The excavation in large size boulder strata with shield method is the restricted zone around the world. So far, there has no mature technology systems for such strata and no typical successful case has been reported. Rock impact breaking mechanism is studied under the conditions of shield tunneling in large size boulder strata with the methods of theoretical analysis, laboratory experiments, numerical analysis and field monitoring. Considering the occurrence features and migration pattern of the large size boulder and its basic physical and mechanical characteristics, the mathematical and mechanical models are established for the rock breaking with cutters to reveal the interaction mechanism between the cutters and the large size boulders (strata) and the internal stress propagating process and crack developing law of rock(mainly the large size boulder) under the impact load of cutters are studied. Based on the Rittinger's new surface theory，the formula for calculating the minimum energy output required to break the large size boulder has been derived，which provided theoretical basis for the setting of shield excavation parameters and the type selection design for shield equipment. The relationship between cutters wearing and Tunnel Boreability of large size boulder strata are disclosed considering the strata abrasiveness characteristics and rock breaking mechanism on impact load. Meanwhile，the model and theory for cutter wear valuation and prediction on basis of the interaction of between surrounding rock and cutters are established，and relevant control technology and countermeasures are also put forward.

富含大粒径漂石地层是盾构工法的禁区，迄今为止，国内外尚无适用该种地层的技术系统和成功的工程案例。采用室内实验、理论分析、数值模拟及现场实测等方法，系统研究了富含大粒径漂石地层盾构刀具冲击破岩机理。考虑大粒径漂石的赋存、运移方式及基本物理力学特征，建立刀具冲击破岩的数学与力学模型，揭示大粒径漂石（地层）与刀具的相互作用机理；研究刀具冲击荷载作用下岩石（大粒径漂石）内部应力传播过程及裂纹发展规律，基于黎金格的新表面理论推导了大粒径漂石破碎所需最低能量输出的计算公式，为盾构的选型设计及盾构掘进参数的设定提供理论基础；开展地层磨蚀性特征研究，从分析大粒径漂石地层可掘进型（Tunnel Boreability）与刀具磨损的关系入手，研究刀具磨损和盾构掘进效率的关系，建立基于“围岩-刀具”相互作用的刀具磨损评估预测模型、理论，提出相关控制技术与对策。

盾构在富含大粒径漂石地层开挖面临着大粒径漂石难以破碎、刀盘刀具磨损严重、盾构掘进效率低下、刀具更换存在风险等难题，该类地层具有漂石含量高、粒径大、强度高、磨蚀性强、流塑性差等特点，给盾构施工带来极大困难。针对施工中遇到的刀具-漂石相互作用、漂石破碎过程及冲击破岩机理、刀盘刀具选型设计及合理布置、刀具磨损特征和掘进速率的预测、盾构掘进控制机制等问题，本项目采用理论分析、数值模拟、实验室物理力学实验、冲击破坏试验与现场工程试验研究相结合的研究手段，深入开展了地层物理力学性质及大粒径漂石冲击破碎实验研究，确定了大粒径漂石的强度、密度、矿物成分、磨蚀性等力学特征，阐明了大粒径漂石在单次冲击和循环冲击不同受力状态下的破碎特征和应力演变机理；分析了大粒径漂石在单刀一次破碎和群刀多次破碎下对的冲击破岩过程及破碎机理，建立了基于能量传递原理的刀具冲击破岩理论及冲击破岩模型，研究了刀具冲击荷载下的漂石裂纹发展过程及刀具破岩所需的最小能量输出，采用数值模拟软件开展了动态破岩过程的数值实现，揭示了刀具与岩石相互作用机理、冲击荷载传递规律及漂石内部裂纹的扩展等规律；结合室内岩石试件的冲击实验分析和刀具破岩机理，开展了冲击破岩刀具的选型设计及合理化布置研究，建立了刀具与大粒径漂石的相互作用力学模型，形成了冲击破岩刀具的结构设计理论与方法，提出了基于富含大粒径漂石地层冲击破岩的盾构掘进控制机制，基于大粒径漂石地层的可掘进性与刀具磨损的关系，提出了盾构施工刀具磨损和掘进速率的预测方法。项目研究提升了青年教师和研究生的科研水平，取得了可观的研究成果，为盾构掘进富含大粒径漂石地层施工控制提供了可靠的理论与技术支持，为盾构重型撕裂刀楔击劈裂破岩机理的推广与应用打下坚实的理论基础。