特大跨度四线深埋隧道施工工法研究——以乌蒙山2号出口车站隧道为例

Construction Methods for Ultra Large-span Four-track Deep Tunnel on Wumengshan No.2 Exit Section

针对特大跨度四线铁路隧道,其开挖面积相当于6倍普通单线铁路隧道,开挖成洞难度大,尚无成功先例。以六(盘水)沾(益)铁路乌蒙山2号出口四线车站隧道工程为背景,通过数值模拟和现场监测,开展特大跨度隧道施工工法研究。研究结果表明:1)通过"撑索转换",即利用"外锚"替换"内撑",实现拱部临时支撑的安全拆除,降低拱部支护体系转换过程中的施工风险,并且突破传统软岩隧道施工中拆撑步长、跳拆等限制,提高了拆撑安全性及灵活性,同时为后续施工提供了较大的工作面。2)通过"以索代撑",即利用锚索取代临时横撑,避免临时撗撑拆除风险,使得开挖更加灵活。3)采用三台阶"撑索转换"及"以索代撑"施工工法,实现了特大跨度隧道台阶法施工。

The construction of ultra large-span four-track tunnel,of which the excavation area equals to 6 times of that of traditional single-track railway tunnel,is difficult;and there is no successful precedent.The construction methods for ultra large-span four-track deep tunnel on Wumengshan No.2 exit section on Liupanshui-Zhanyi Railway are studied by numerical simulation and site monitoring methods.The results show that:1)By using temporary support replaced by prestressed anchor,the temporary support of arch is successfully dismantled,the replacing construction risk of arch is reduced;the disadvantages of traditional soft rock tunnel construction are overcome;the safety and flexibility of support dismantling are improved;and large working face can be provided for followed construction step.2)By using temporary cross-brace replaced by prestressed anchor cable,the temporary cross-brace dismantling risk is avoided;and the construction flexibility is improved.3)The three-bench excavation of ultra large-span tunnel is realized by using temporary support replaced by prestressed anchor and temporary cross-brace replaced by prestressed anchor cable.