复杂地形、地质情况下大跨度隧道洞口段设计

研究目的:大跨度隧道洞口地段地形地质情况复杂,对隧道施工和结构影响较大,结合渝怀线大板溪隧道洞口特殊地段的处理,对复杂地形、地质情况下大跨度洞口段设计进行小结。研究方法:针对本工程的地形、地质条件,采用工程类比和结构分析的方法,确定经济合理的处理措施,并对结构进行检算和分析。研究结果:针对大板溪隧道洞口段特殊的地形、地质情况采取有效的处理措施,取得了良好的效果。研究结论:大跨度隧道洞口段,对顺层偏压地段,可于靠山侧适当范围设置预加固桩,消除山体滑移对线路和结构物的危害;对地形十分陡峻,且衬砌基础存在软弱围岩地段,为减少开挖对山体的扰动,于靠山侧设置锚杆挡墙减少刷方高度,采取反压混凝土及配合超前大管棚的施工方法,解决了进洞难的问题;同时设置两侧边墙不等厚的衬砌结构形式,软弱围岩基础设置桩基托梁,将衬砌外侧基础置于桩基托梁上,解决了衬砌结构设计的难题。

Design of Tunnel Portal Section with Large Span in Complicated Terrain and Geology Area

Research purposes: The complicated terrain and geology in the tunnel portal section with large span has a great influence on the tunnel construction and structure.Combined with the disposal of special section in the Dabanxi tunnel portal,this paper has made a brief summary on the design of the portal section with large span in the complicated terrain and geology area. Research methods:According to the terrain and geology condition in the engineering project,and adopted the methods of engineering analogy and structure analysis,this paper determines the economical and reasonable treatment measures and carries out the check and analysis of structure. Research results:Treat measures for the special terrain and geology in the tunnel portal section of Dabanxi tunnel have good effects. Research conclusions:Because of the limitation of route,terrain and geology condition in the portal section of tunnel with large span,it is difficult to enter the tunnel and dispose the structure.In the bedding side-pressure section,the pre-consolidating piles can be set within the proper scope near the mountain side to eliminate the hazard of mountain sliding to the route and structure.There should be some space for the length and setting scope of pre-consolidating pile to increase some safety reserves.In the section with steep terrain and lining foundation where there is soft-weak surrounding rock,the rockbolt retaining wall shall be set near the mountain side for reduction of cutting height to reduce disturbance of excavation to mountain body and the construction method to back-press concrete and cooperate the advance pipe shed support shall be taken to solve the difficulty to enter the tunnel.At the same time,the structural form with different thickness on both sidewalls on two sides is adopted and the pile foundation spandrel beam is set in the soft-weak surrounding rock foundation and the external foundation of lining is set on the pile foundation spandrel beam to solve the design of the lining structure.