富水砂层中地铁盾构隧道下穿既有铁路病害桥施工的风险分析及控制措施

Risk Analysis and Control Measures for Shield Tunneling of Metro Crossing under Existing Railway Diseased Bridges in Rich Water Sand Strata

目的:在富水砂层中新建的地铁盾构隧道下穿既有铁路病害桥时,会增大施工风险,需对施工进行风险分析,并制定针对性的控制措施。方法:介绍了南昌轨道交通4号线起凤路站—七里站区间下穿京九铁路工程的概况,对该工程施工的风险进行了识别与分析。基于FLAC3D软件建立了数值模型,设置了与之相匹配的材料参数,以模拟盾构的掘进过程。设置了3种施工工况,对不同工况下的地面沉降、既有铁路路基沉降进行了数值计算,确定该工程采用工况三(地层注浆加固+框架涵加固)作为施工控制措施。针对工况三的控制措施,制定了实际施工的监测方案,并对实测数据进行了分析。结果及结论:合理的盾构机下穿参数可有效降低地面沉降和铁路路基沉降,工况三的控制措施可以很好地解决铁路病害桥敏感性高、整体稳定性差等问题,进而降低了盾构下穿施工的风险。

Objective:In the case of constructing a new subway shield tunnel crossing an existing diseased railway bridge in a rich water sand layer,due to the possibilities of increasing construction risks.A risk analysis of the construction needs to be carried out,and specific control measures need to be formulated to address the risks.Method:The project of crossing Beijing-Kowloon Railway by Nanchang rail transit Line 4 from Fenglu Station to Qili Station is overviewed,the construction risks of the project are identified and analyzed.Based on the FLAC3D software,a numerical model is established with matching material parameters to simulate the shield tunnel excavation process.Three construction conditions are set,and numerical calculations are performed on ground subsidence and existing railway subgrade settlement under different conditions.It is determined that the project should adopt Construction Condition III(layer grouting reinforcement+framed culvert reinforcement)as the construction control measure.Regarding this measure,a monitoring plan for actual constructions is formulated,and the measured data are analyzed.Result&Conclusion:Reasonable parameters for shield machine tunneling can effectively reduce ground settlement and railway subgrade settlement.The above control measures can effectively address issues such as high sensitivity of railway diseased bridge and poor overall stability,thus reducing the risks of shield tunneling construction.