新人工填筑土地层超大断面隧道施工导致的地表沉降及其控制措施

Ground Settlement of New Artificial Filling Soil Layer Induced by Constructing Tunnel with Super Large Cross-Section and Its Control Measures

以贵阳立体交通枢纽工程龙洞堡机场隧道工程为背景,综合运用现场测试、模型试验及数值计算方法,对超厚新人工填筑土地层超大断面隧道施工导致的地表沉降及其控制对策进行研究。基于实测的隧道拱顶沉降,根据既有的计算方法计算拱顶全部沉降;通过室内模型试验和三维数值模拟得到因地层损失引起的地表沉降占拱顶全部沉降的比率;根据拱顶全部沉降和比率计算得到隧道施工导致的地表沉降;再根据实测的地表总沉降,确定隧道施工和土体自身固结分别导致的地表沉降占地表总沉降的比例。结果表明:隧道施工导致的地表沉降是拱顶沉降的35%~36%,占地表总沉降的20%~34%,土体固结导致的地表沉降占地表总沉降的66%~80%,可见土体固结是导致地表沉降的主要因素。由此提出控制地表沉降的主要对策:通过地表钢管桩注浆加固,对土层进行改良;对拱部进行中管棚超前支护;采用大拱脚弧形导坑预留核心土台阶法开挖隧道;设置H175型钢钢架加强初期支护,二次衬砌尽可能地紧跟初期支护施作。

Taking the Longdongbao airport tunnel which is the three-dimensional transportation hub project in Guiyang as the background,the ground settlement laws and countermeasures of super-thick new artificial embankment soil constructing in tunnel with super large cross-section were researched by the methods of field test,model test and numerical calculation.Based on the measured vault subsidence and the existing calculation method,the total vault subsidence was calculated.According to indoor model test and three-dimensional numerical simulation,the proportion of ground settlement caused by ground loss to the total vault subsidence was acquired.In the light of the total vault subsidence and the proportion,the ground settlement caused by tunnel construction was obtained.Then on the basis of the measured total ground settlement,the proportion of ground settlement caused by tunnel construction and the consolidation of soil respectively to the vault ground settlement was determined.Results show that the ground settlement caused by tunnel construction,accounting for 20% ~34% of the total ground settlement,is35%~36% of the vault subsidence,the ground settlement caused by the consolidation of soil accounts for66%~80% of the total ground settlement.Thus it can be seen that the consolidation of soil is the main factor leading to ground settlement.The main countermeasures for controlling ground settlement are put forward：improving the soil through the grouting reinforcement of steel pipe pile on ground;applying advance support to the arch using middle pipe shed;excavating tunnel by bench cut method with big arch springing,arc leading pit and reserved core soil;setting the H175 steel frame to strengthen the initial support and the secondary lining following the initial support as quickly as possible.