渝昆高铁华山松隧道穿越凝灰岩段施工工法分析

Construction Method Analysis of Huashansong Tunnel Crossing Tuff Section of Chongqing-Kunming High-Speed Railway

【目的】凝灰岩地层容易遇水软化,自稳能力差,隧道穿越时极易发生溜塌、大变形等灾害,这就需要研究在破碎凝灰岩段隧道采用两台阶与三台阶工法下,围岩、支护结构受力及变形规律,为施工提供理论指导。【方法】以在建渝昆高铁华山松隧道为背景,通过数值模拟手段进行计算分析。【结果】研究结果表明:采用三台阶开挖时,变形情况较两台阶有一定程度的改善,其中整体最大沉降量降低14%,特征断面沉降量降低9%;在支护结构受力方面,三台阶法要比两台阶法稍有优势。隧道开挖后,为避免隧道两侧边墙部位出现压应力集中,施工中应注意观察边墙初支是否有开裂、鼓包等现象,必要时施作临时横撑,以保证施工安全。【结论】研究成果可为今后类似工程提供参考。

[Purposes]The tuff stratum softens when it meets water,and its self-stabilizing ability is poor,so it is prone to collapse and large deformation disasters when the tunnel passes through.This paper provides theoretical guidance for studying the stress and deformation law of surrounding rock and supporting structure under the two-step and three-step construction methods used in the tunnel with broken tuff section.[Methods]Based on the Huashan pine tunnel of Chongqing-Kunming high-speed railway under construction,this paper makes calculation and analysis by means of numerical simulation.[Findings]The results show that the deformation is improved to some extent when the three-step excavation is used,in which the overall maximum settlement is reduced by 14% and the settlement of the characteristic section is reduced by 9%.The three-step method is slightly superior to the two-step method in the stress of supporting structure.After the tunnel excavation,in order to avoid the concentration of compressive stress on the side walls on both sides of the tunnel,attention should be paid to observing whether the initial support of the side walls is cracked and bulged,and temporary cross bracing should be applied when necessary to ensure the construction safety.[Conclusions]The research results can provide construction reference for similar projects in the future.