列车动载-地下水耦合致围岩劣化和隧道仰拱疲劳损伤的作用机制

After a tunnel was completed, groundwater gathered at the bottom of the tunnel arch. The reciprocating train load intrigued the groundwater and transient high water pressure was produced. As a result, the surrounding rock particles were flushed and eroded, which caused the surrounding rock deterioration and formed intact contact with tunnel arch. Because of the loss of particles, some voids appeared which weakened the support stiffness, however, increased arch damage. During the operation period, this interaction repeated and more surrounding rock deterioration and arch damage were formed and the stresses under arch change a lot. It has been extensively investigated and analyzed that the diseases were caused by three main factors, dynamic train load, underground water and the intact contact between the tunnel arch and its surrounding rock. To clarify the interaction mechanism of the three factors, this study especially aims at the dynamic pressure fluctuation between the tunnel arch and the surrounding rock caused by railway tunnel train vibration, the deterioration law of the surrounding rock and concrete structures and the deformation principals of tunnel concrete, the dynamic water pressures changing with time and space and the surrounding rock erosion caused by the high water pressure are elaborately studied. The expectation results are to achieve the principles of the railway train load passing to the bottom of the tunnel, the distributing characteristics of dynamic pressure caused by the train load, the mechanical parameters changing from the load and the damage of concrete structures. With these studies, the vibration loads of railway tunnel can be achieved, the deformation mechanisms of tunnel concrete and surrounding rock when incomplete contact occurs can be achieved. Finally, a dynamic model to explain the mutual functions between surrounding rock deterioration and arch fatigue damage will be given. With the results achieved from this study, the damages and diseases caused by underground water, train load and surrounding rock with defects can be explained. In addition, these achievements can be applied to solve similar problems which also occur in the railway tunnels and subway tunnels.

列车往复振动使积聚在隧道仰拱底部的地下水产生瞬态高水压，冲刷、磨蚀隧底围岩表面颗粒，造成围岩劣化，形成了围岩和仰拱间的不连续接触。导致仰拱结构支撑条件减弱，损伤加剧，反过来就加重了隧底围岩劣化，二者交互作用显著。为探明列车动载-地下水耦合作用下隧底围岩劣化和仰拱结构疲劳损伤的交互作用机理，本项研究对列车动载-地下水耦合作用下软弱围岩的劣化规律开展研究，获得其物理力学参数的变化规律，建立评价方法；明确劣化后围岩和仰拱结构间的接触形态，揭示出围岩劣化导致支撑条件弱化时的仰拱结构层间接触应力时空变化规律；形成围岩劣化导致仰拱结构受损加剧，而仰拱结构受损加大列车振动的动应力，使隧底围岩劣化加剧这一交互作用机理，最终建立起隧底围岩劣化和仰拱结构损伤交互作用下的仰拱结构累积损伤动力模型。这一研究成果将为类似科学问题的解释提供理论基础和数据支撑。

随着我国高速铁路和重载铁路的迅速发展，列车速度及列车轴重不断增加，列车荷载所产生的振动与冲击作用日益增强。在有地下水的土质围岩隧道，当列车经过时会产生骤然升高的动水压力，导致基底土颗粒流失而产生底部不连续接触，最终影响仰拱结构。本项目采用了自行设计的室内激振试验以及地下水作用下的颗粒流失等室内试验、对张唐铁路等隧道现场测试数据进行了手机与分析、综合采用了理论分析和数值技术等手段，分析了渗流作用下砂性土围岩内部细颗粒的渗透迁移规律，基于砂性土围岩细颗粒的侵蚀及沉积定律，建立了渗流作用下的围岩流失率计算方法；采用建立的计算方法分析了列车动载-地下水耦合作用下隧底砂性土围岩流失规律，通过折减围岩弹性反力系数模拟围岩劣化，提出了隧底砂性土围岩流失率控制标准。探明了地下水骤升的动水作用规律，建立了列车动载-地下水耦合作用下隧底砂性土围岩劣化的CFD-DEM耦合分析方法，构建了渗流作用下砂性土围岩颗粒的起动流失过程。基于损伤累积模型，建立了有空隙条件下隧底结构的损伤规律，揭示了受损条件下的层间接触压力传递规律，建立了列车动载-地下水耦合作用下隧底结构剩余寿命的预测方法，从机理上解释了隧道结构底部脱空的渐变问题，在理论上建立了基于弹性抗力折减的力学计算方法，可为轨道交通类的隧道结构设计提供一定的理论依据和技术参考。以上成果应用于张唐铁路等隧道结构设计中，推广应用效果显著。