重载列车激励作用下隧道底部围岩劣化机理及其对结构力学行为的影响

The tunnel structure will produce remarkable static and dynamic effects, and the development of structural fatigue damage directly affects its durability when a Heavy-haul train passes through. The deterioration and void of surrounding rock caused by coupling effect of dynamic load and groundwater will aggravate the dynamic response and fatigue damage of tunnel basement structure. The main purpose of this study is based on the excitation test and remote monitoring of heavy-haul railway tunnels and remote monitoring, indoor test simulation method for dynamic response of tunnel structure under the excitation of heavy-haul train under water-rich condition is established. On this basis, combined with the measured long-term variation of water pressure at the bottom surrounding rock, the void evolution process and deterioration mechanism of the bottom surrounding rock under the comprehensive influence of groundwater-train dynamic load are clarified, based on this, deterioration critical conditions and attenuation law of physical parameters of the bottom surrounding rock are obtained. Based on layered elasticity theory and stress diffusion angle, dynamic load calculation models of single-track and double-track heavy haul railway tunnels under ideal and deteriorated surrounding rock are proposed respectively. Based on Miner's linear fatigue theory, a fatigue life prediction method for different parts of the basement structure of heavy haul railway tunnel is obtained, the influence of surrounding rock deterioration on fatigue damage distribution of tunnel bottom structure is further obtained. The research can provide theoretical support for similar projects in design of heavy-haul railway tunnel and improve the current situation in which ordinary railway tunnel code are applied qualitatively.

重载列车通过时，隧道结构会产生显著的静动力学效应，结构的疲劳损伤发展直接影响其耐久性，同时重载列车动荷载与地下水耦合作用引起的围岩劣化脱空会加剧隧底结构的动力响应及疲劳损伤程度。本课题的主要目的是基于重载铁路隧道原位激振试验和远程监控，建立富水条件重载列车激励作用下隧道结构动力响应的室内试验模拟方法；在此基础上，结合实测底部围岩水压力长期变化规律，明确地下水-列车动载综合影响下底部围岩的脱空演变过程和劣化机理，并据此得出底部围岩的劣化临界条件和物理参数衰减规律；基于层状弹性理论和应力扩散角分别提出理想和围岩劣化2种状态下单线和双线重载铁路隧道的隧底结构动荷载计算模型；基于Miner线性疲劳理论获得重载铁路隧道底部结构不同部位的疲劳寿命预测方法，并进一步获取围岩劣化对隧底结构疲劳损伤分布的影响。本项目的研究可为重载铁路隧道设计类似项目提供理论支撑，改善其定性套用普通铁路隧道规范的现状。

重载列车动荷载与地下水的共同作用是导致底部围岩劣化脱空并加剧隧底结构疲劳损伤的主要因素。围岩在列车激励作用下的劣化会使底部结构的支撑条件下降，进而影响隧底结构动力特征和疲劳损伤发展规律。目前相关研究成果十分有限，重载铁路隧道设计多是套用普通铁路隧道规范。明确重载铁路隧道底部围岩劣化机理和形成过程，得到隧底结构动力特征和疲劳损伤发展规律对重载铁路隧道的设计和运营具有指导意义。. 本项目根据瓦日铁路太行山隧道的水土压力长期效应将底部围岩脱空劣化过程分为4个阶段，结合室内试验和离散元分析，进一步揭示了围岩脱空临界条件和劣化程度。结合重载铁路隧道底部结构各部位的实测数据，明确了各层表面动荷载分布及大小，在此基础上提出了道床结构表、底面，仰拱结构表面和围岩表面动荷载拟静力计算方法并构建了动荷载计算模型。最后基于名义应力法的疲劳损伤理论，得到了底部结构不同部位在不同围岩条件、不同轴重下条件下的疲劳寿命预测方法并进一步探究了围岩劣化位置和程度对其影响。主要结果：1）重载列车动荷载作用下隧道底部围岩的脱空劣化机理；2）隧底结构各结构层表面的动荷载拟静力和动力计算方法；3）围岩理想状态和脱空劣化形成后2种条件下隧底结构的疲劳损伤演变规律和寿命预测方法。研究成果为完善重载铁路隧道设计和运营提供研究基础。