黄土隧道马蹄形盾构工法选择及应用

Selection and Application of Horseshoe-shaped Shield to Loess Tunnel

目前铁路隧道施工以矿山法为主,但在黄土等软弱围岩隧道施工时风险大、进度慢;而盾构法已在地铁、水下隧道等软弱地层中得到了广泛应用。针对蒙华铁路砂质新黄土隧道:1)通过矿山法与盾构法比较确定采用盾构法施工。2)从开挖内轮廓、刀盘开挖特点、管片拼装方式、管片受力及配筋4个方面对马蹄形盾构隧道和圆形盾构隧道进行对比分析,得出马蹄形盾构隧道的断面利用率更高,马蹄形管片与圆形管片受力有所差别而马蹄形管片配筋量更低。3)介绍马蹄形盾构设备概况,并对马蹄形管片设计进行研究。4)例举马蹄形盾构掘进过程中遇到的防寒防冻、管片底部开裂和遇到含姜石的老黄土掘进困难等问题以及相应的处理措施。经过1年多的施工实践证明,在黄土隧道马蹄形盾构施工风险低,质量高,安全可靠。

At present,the mining method,with high risk and low advancing speed in loess,is the main construction method for railway tunnels. However,the shield method has been widely used in metro and underwater tunnels. In this paper,the sandy new loess tunnel on Menghua Railway is taken for example. 1) The shield method is chosen by comparing to mining method. 2) Comparison is made between horseshoe-shaped shield tunnel and circular shield tunnel in terms of excavation inner contour,excavation characteristics of cuterhead,segment assembling mode and stress and steel bar arrangement of segment. It is shown that the horseshoe-shaped shield tunnel has a higher utility rate of crosssection comparing to circular shield tunnel; the stresses of horseshoe-shaped segment and circular segment are different;but the steel bar arrangement of horseshoe-shaped segment is lower than that of circular segment. 3) The general situation of horseshoe-shaped shield is presented; and the design of horseshoe-shaped shield segment is studied. 4) The difficulties,i. e. freezing prevention, cracks on segment bottom and calcareous concretion in old loess tunnel,encountered during horseshoe-shaped shield tunneling and corresponding countermeasures are put forward. The practice and application of horseshoe-shaped shield indicate that the horseshoe-shaped shield tunneling in loess tunnel can reduce the construction risk,improve the construction quality and guarantee the construction safety.