浅埋偏压隧道洞口段软弱围岩失稳机制分析

摘要

浅埋偏压隧道洞口段极易发生围岩失稳,本文以沪昆客专湖南段田家山隧道为例,基于现场地质调查,分析围岩变形破坏特征,从地质角度探讨浅埋偏压隧道洞口段围岩失稳的影响因素,基于监测数据并运用数值模拟方法研究围岩失稳机制,总结围岩失稳破坏模式,提出针对性的处治措施.研究表明:围岩失稳是多因素协同作用的结果,浅埋偏压作用和地下水是造成围岩失稳的关键因素;围岩破坏模式可归结为重力坍塌和膨胀内鼓的协同破坏模式;在围岩失稳机制分析的基础上,提出了“地下+地表”的综合处治措施,可有效地控制围岩变形.%The surrounding rock instability in shallow-buried tunnel portal section under unsymmetrical pressure is prone to occur.For this problem,taking Tianjiashan Tunnel at Changsha to Kunming Section in Shanghai-Kunming High-speed Railway for example,the deformation characteristics of surrounding rock are analyzed based on field geologic survey.The incentive of surrounding rock instability is discussed from geology aspect.Then,basing on deformation monitoring and numerical simulation,the instability mode is concluded.At last the targeted treatment methods are proposed.The results show that the surrounding rock instability is a result of multifactor synergism.Shallow buried,unsymmetrical pressure and groundwater are main factors of the surrounding rock instability.The surrounding rock failure mode of shallow biased opening section can be concluded as the synergistic failure mode of gravitational collapse and dilatancy.Based on analyzing tunnel collapse mechanism,ground and underground comprehensive treatment measures are proposed,so as to control the deformations of surrounding rock effictively.