大断面富水复合地层铁路隧道施工关键技术

干庆隧道穿越复合地层。复合地层以饱和粉质黏土为主,间夹粉细砂或砂类土、圆砾类土及半胶结状砂层,组成无规律,结合性能弱,黏聚力低,自稳能力极差,可借鉴成功经验少,施工难度大。为解决施工遇到的技术难题,以干庆隧道为研究背景,通过分析施工影响因素,提出解决措施。为解决富水地层地下水对施工的影响,采用地表大口径深井群井降低地下水位技术、超前短距离管棚快速预注浆预加固围岩。为解决大断面及复合地层施工中的安全风险,加快施工进度,采用多台阶划小施工单元进行开挖、旋喷桩加固拱脚及液压破碎锤精准开挖技术。采用以上技术措施后,该隧道安全快速地通过了富水、复合围岩软弱地层,平均月进尺达30 m,最高达42 m,取得了较好效果。

Key Technologies in Construction of Railway Tunnel in Large Cross-section and Rich-water Composite Stratum

Gan-qing tunnel crosses rich-water stratum. The tunnel surrounding rocks are mainly silty clay mixed with silty-fine sand,sandy soil,granular soil and other semi cemented sand. All kinds of surrounding rocks are scattered randomly in weak performance,low cohesion and poor self stability stratums. There have been less engineering experiences to refer to and construction is very difficult. In order to solve the technical problems encountered in construction,and to provide a successful example of tunnel excavation,Gan-qing tunnel excavation is studied. In order to solve the impact of groundwater on construction,group of large diameter deep wells are employed to lower underground water level and advance short pipe roof quick grouting to reinforce surrounding rock. In order to reduce the security risks of large section construction,multiple steps with small construction unit,oblique rotary spray pile reinforcement arch foot and precision hydraulic hammer excavation technology are used. All these measures allow the tunnel excavation to pass though rich-water composite soft rock strata quickly and safety with average 30 m and maximum 42 m per month.