川中红层软岩高速铁路隧道基底上拱机理研究

Research on the Mechanism of Base Arching in Red Stratum Soft Rock High-speed Railway Tunnel in Central Sichuan

研究目的:由于川中红层其特殊的物理力学性质,区域内多个高速无砟铁路隧道发生基底上拱病害,严重影响铁路运行安全。本文以川中软岩某高速铁路隧道为研究对象,结合实际工程地质条件和现场调查,概化物理模型,通过离心模型试验、数值模拟,分析开挖前后法向与水平应力大小关系,研究侧压力系数、软岩埋深、软岩层厚对基底上拱的影响,以期为铁路勘察设计提供技术帮助。研究结论:(1)法向与水平应力的相对大小是造成隧道及其下伏地层上拱的关键因素,开挖后地应力的变化是导致基底发生上拱病害的重要原因;(2)软岩夹层改变了夹层内及其下部地层位移矢量方向,也大大增加了基底上拱量;(3)隧道基底最大上拱量随初始侧压系数增加而增大,最大上拱地层深度和范围随着初始侧压系数、软岩埋深和软岩层厚的增加而减小;(4)本文研究可为运营铁路工程整治措施提供参考。

Research purposes:The special physical and mechanical properties of the red layer in Sichuan have led to the disease of the base arching of many high-speed railway tunnels in the region,which has seriously affected the safety of railway operation.This paper takes a high-speed railway tunnel in soft rock of the red layer in Sichuan as the research object,combines the actual engineering geological conditions and field investigation,generalizes the physical model,analyzes the relationship between normal and horizontal stress before and after excavation through centrifugal model test and numerical simulation,and studies the influence of lateral pressure coefficient,soft rock depth and soft rock thickness on the base arching,to provide technical help for railway investigation and design.Research conclusions:(1)The relative magnitude of normal stress and horizontal stress is the key factor to cause the upper arch of tunnel and its underlying floor.The change of ground stress after excavation is an important reason to cause the upper arch disease of base.(2)The soft rock interlayer changes the displacement vector direction of the strata in the interlayer and its lower part,and also greatly increases the camber of the base.(3)The maximum camber amount of the tunnel base increases with the increase of the initial lateral pressure coefficient,and the maximum camber formation depth and range decrease with the increase of the initial lateral pressure coefficient,the buried depth of soft rock and the thickness of soft rock.(4)The research result can provide reference for the regulation measures of operational railway engineering.