超浅埋淤泥富水地层大断面隧道开挖施工技术研究

Research on Construction Technology of Large Section Tunnel Excavation in Ultra⁃Shallow Buried Silt Water⁃Rich Stratum

针对超浅埋淤泥富水地层大断面隧道开挖易坍塌、支护难度高等问题,以重庆轨道交通24号线一期工程鹿角车辆段出入段线隧道RSK1+337.861~RSK1+406.306断面施工为工程背景,提出了“环形CD+台阶法预留核心土法”施工技术。并使用Midas GTS NX数值模拟软件建立三维模型,分析隧道围岩总位移量和支护结构应力,进而验算该项施工技术的合理性,并预测隧道开挖的薄弱部位。根据模拟结果判定:隧道拱顶为施工过程中的薄弱部位,隧道拱顶的最大沉降值为6.69 mm,拱腰净空收敛值最大为2.48 mm,均满足规范要求。最后,通过监测结果表明,典型断面拱顶沉降及净空收敛与模拟结果基本一致,均能满足规范设计控制值。本技术对类似超浅埋淤泥富水地层大断面隧道开挖具有一定的参考价值。

Aiming at the problems of easy collapse and high difficulty of support in excavation of large section tunnel in ultra⁃shallow buried silt water⁃rich stratum,this paper takes the construction of section RSK1+337.861~RSK1+406.306 of Lujiao Car Depot of Chongqing Rail Transit Line 24 Phase I project as the engineering background,and proposes the construction technology of“circular CD+step method for reserving core soil method”.Midas GTS NX numerical simulation software is used to establish a three⁃dimensional model.By analyzing the total displacement of the surrounding rock and the stress of the supporting structure of the tunnel,the rationality of the proposed construction technology is determined,and the weak parts of the tunnel excavation are predicted.According to the simulation results,the tunnel arch is the weak link in the construction process.The maximum settlement value of the tunnel arch is 6.69 mm,and the maximum convergence value of the arch waist is 2.48 mm,both of which meet the construction requirements.Finally,the monitoring results show that the arch roof settlement and headroom convergence of typical section are basically consistent with the simulation results,and both can meet the standard design control values.The construction technology provides valuable reference for subsequent excavation of large⁃section tunnels in ultra⁃shallow buried silt water⁃rich stratum.