铁路黄土隧道施工变形规律及预留变形量研究

为研究黄土隧道施工变形规律及预留变形量,以蒙华铁路双线黄土隧道工程施工为依托,采用现场实测和统计分析的方法分析隧道周边位移变形规律,以确定黄土隧道设计预留变形量。双线黄土隧道施工的变形规律表现为:隧道开挖时,拱顶下沉和周边收敛发展较快,仰拱封闭后,变形趋于稳定;隧道拱顶下沉大于周边收敛。Ⅳ级围岩黄土隧道下沉速率集中分布在5 mm·d~(-1)以内,部分深埋断面速率大于5 mm·d~(-1)。Ⅴ级围岩黄土隧道深埋时,拱顶下沉较小,速率集中分布在5 mm·d~(-1)以内;浅埋时,部分断面拱顶下沉超出设计预留变形量,速率在15mm·d~(-1)以内;其表现出的特点是:浅埋变形大,速率大。净空变形特征值的均值在浅埋时为4.1,深埋时为2.2。Ⅳ、Ⅴ级围岩黄土隧道设计预留变形量建议值分别是8~10 cm、12~15 cm。

Study on Deformation Law and Preset Deformation of Railway Tunnels in Loess

In order to study the deformation law and the amount of deformation of the loess tunnel,the deformation law and the preset deformation of the tunnel are analyzed by field measurement and statistical analysis method based on the Menghua Railway double track loess tunnel construction.The deformation of the double-lined loess tunnel demonstrates that the excavation of the tunnel,the crown settlement and the surrounding convergence are developing rapidly after tunnel excavation,and the displacement becomes stable after the invert is closed.The subsidence rate of the loess tunnels in grade Ⅳ is concentrated within 5 mm·d~(-1) and part of the deep buried section rate is greater than 5 mm·d~(-1).When the tunnel of gradeⅤ surrounding rocks is deep buried,the crown settlement is small and the velocity is concentrated within5 mm·d~(-1); for shallow buried tunnel,the deformation of partial crown section is more than the designed preset value and the rate is within 15 mm·d~(-1),which is characterized by larger deformation and rate for shallow buried tunnel.The mean clearance deformation characteristic value is 4.1 for shallow buried and 2.2 for deep buried.The recommended preset deformation range of loess tunnel of grade Ⅳ surrounding rocks is 8 cm to 10 cm,and 12 cm to 15 cm for grade Ⅴ surrounding rocks.