中文摘要：

以重庆轨道交通5号线3标里程DK18＋138.948~DK18＋191.964区间浅埋扁平超大断面隧道工程为依托,对隧道围岩变形及双侧壁导坑法预留核心土开挖合理长度进行研究.采用数值分析软件MIDAS-GTS建立了核心土长度分别为20m、25m、30m隧道三维实体模型,将计算值与现场实测数据进行对比,验证了本文方法的正确性和有效性.通过地表沉降、围岩变形、掌子面附近拱顶下沉、掌子面挤出位移等方面综合分析,最终确定依托工程双侧壁导坑法核心土开挖的合理长度为25m,且不宜大于研究段隧道长度的1/2.本文的方法和结论为此类扁平超大断面隧道核心土留设合理长度问题的研究提供参考,并为施工提供理论支持.

英文摘要：

Based on the project of DK18＋138.948~DK19＋191.964 tunnel section in Chongqing Metro 5 line 3 mark,the rational length of core soil of double side slope method used in the project and deformation of tunnel surrounding rock were studied.Three-dimensional finite element model of core soil length with 20 m,25 m and 30 m were established by numerical analysis software MIDAS-GTS.The construction phase had been truly simulated.The correctness and validity of the method used in this paper were verified by comparing the calculated values with the field measured data.The calculated values are in good agreement with the measured data.The measured values are slightly larger than the calculated values,but they are in the same orders of magnitude.Relied on the comprehensive analysis of ground surface settlement,surrounding rock deformation,vault settlement near the tunnel working face and extrusion displacement of tunnel working face,the rational length of core soil of double side slope method used in the project is 25 m,which should not be greater than 1/2 of tunnel length.The conclusion is only for the surrounding rock conditions of the project.The method and conclusions of this paper provide a reference for the study of rational length of core soil used in flat shallow super section tunnel and a theoretical support for the construction.The method used in actual project and the effect are good.