昔格达地层隧道围岩及初期支护变形规律研究

为探明昔格达地层隧道开挖过程中初期支护背后空隙注浆的时机以及预留变形量的大小,以成昆复线铁路昔格达地层隧道为背景,采用现场实测与统计分析的方法对昔格达地层隧道围岩和初期支护的变形规律以及预留变形量进行深入分析。研究结果表明:1)昔格达地层隧道上台阶开挖后初期支护与围岩间存在初始空隙,拱顶围岩与初期支护间的差异沉降为1~2 mm,受地质、埋深及施工等因素影响,中台阶开挖较易引起隧道塌方,建议中台阶开挖前对拱部初期支护背后的空隙进行注浆回填。2)昔格达地层隧道预留变形量可根据掌子面施工揭示围岩情况调整,若施工揭示的昔格达组以页岩为主,建议预留变形量设置为24~30 mm;若施工揭示的昔格达组以砂岩为主,建议预留变形量设置为118~123 mm。

Study of Deformation Law of Tunnel Surrounding Rock  and Primary Support in Xigeda Formation

The backfill grouting time of hollow behind primary support of tunnel on Chengdu Kunming Double track Railway of Xigeda Formation and the reserved deformation need to be cleared. As a result, the deformation law of tunnel surrounding rock and primary support and reserved deformation in Xigeda Formation are further studied by site monitoring and statistical analysis method. The study results show that: 1) There is initial gaps between surrounding rock and primary support after top heading excavation; the differential settlement between surrounding rock and primary support of tunnel crown top is 1-2 mm; as a result of geological conditions, tunnel buried depth and construction conditions, middle bench excavation induced tunnel collapse should be paid attention to and backfill grouting should be carried out for hollow behind arch primary support before middle bench excavation. 2) The reserved deformation can be appropriately adjusted based on construction situation of tunnel face; the reserved deformation should be 24-30 mm when the shale takes the main component of Xigeda Formation, and that should be 118-123 mm when the sandstone takes the main component of Xigeda Formation.