层厚比对互层地层隧道围岩稳定性的影响探究

Research on the Influence of Thickness Ratio on Surrounding Rock Stability of Tunnel in Interbedded Strata

研究目的:互层围岩开挖易出现台阶溜垮、涌水涌砂等现象,为安全施工,本文以蒙华铁路阳城隧道第四系土砂互层地层隧道围岩为研究对象,通过室内试验、现场试验及数值模拟等方法,探究层厚比对围岩稳定性的影响规律。研究结论:(1)土砂互层地层隧道围岩,黏聚力和内摩擦角随层厚比变化趋势相反;(2)两层土砂互层地层围岩随着土层所占比例的增加,隧道拱顶沉降呈现先减小后增大的规律,两层、三层土砂互层地层围岩土砂比为1∶1或1∶1∶1均匀分布时,拱顶沉降和周边收敛最小,初期支护结构主应力差最小,围岩稳定性最好;(3)不同层厚比土砂互层地层隧道,拱脚水平位移比拱肩水平位移更大,波动范围更广,隧道施工中应尤其加强对拱脚位置处的支护;(4)本研究结果可为土砂互层地层隧道围岩稳定性的进一步研究提供参考,为互层地层隧道的设计和施工提供借鉴。

Research purposes:In the excavation of interbedded surrounding rock,the phenomena such as steps slipping and water and sand gushing are easy to occur.In order to ensure safe construction,taking the surrounding rock of Quaternary soil-sand interbedded of Yangcheng Tunnel of Menghua Railway as the research object,the influence of ratio of layer thickness on the stability of surrounding rock is studied by the means of laboratory test,field test and numerical simulation.Research conclusions:(1)The cohesive force and internal friction angle of the tunnel surrounding rock mass are opposite to that of the ratio of layer thickness.(2)With the increase of the proportion of soil layer in the two layers of interbedded rock,the absolute value of the displacement of the tunnel vault first decreases and then increases.When the ratio of rock-soil to sand in the two-layer and three-layer inter-layer is 1∶1 or 1∶1∶1,the settlement of the dome and the surrounding convergence are the minimum,the principal stress difference of the initial supporting structure is the minimum,and the surrounding rock stability is the best.(3)The horizontal displacement of arch foot is larger and the fluctuation range is wider than that of arch shoulder in tunnel with different layer thickness ratio.The support of arch foot should be strengthened in tunnel construction.(4)The research results can provide reference for the further study of surrounding rock stability of tunnels in soil-sand interbedded strata and for the design and construction of tunnels in interbedded strata.