It is great significance to control the ground surface settlement in the subway tunnel construction.Es-pecially when subway tunnel excavation pass through a high filling area of crushed rock soil in the downtown area.How to ensure the stability of surrounding rock hole and control the ground surface settlement is a key tech-nical problem.The paper presents an example that tunnel excavation pass through complex geological area of metro line no.3 project in Chongqing.At first,the problems that the big surface subsidence and structures crack-ing appear in the process of the tunnel excavation and discussed.Then,the three dimension finite element model of the tunnel-soil-structures interaction according to the actual excavation process are set up to analysis and evaluation the causes of construction settlement.Based on the analysis and calculation results,many technical measures are proposed.Such as small catheter grouting consolidation,CD construction method,excavation speed control and so on.The monitoring results show that the vault sinks and convergence value reduce signifi-cantly after the improved technology measures are used.At same time,the ground surface settlement is controll-ed effectively.The results show that the improved construction measures realize the purpose of control surface settlement.The 3D numerical simulation analysis method can provide reference for the similar project.%控制地表沉降对于地铁隧道的施工意义重大,尤其是在闹市区穿越块、碎石土填方地带时如何保证洞内围岩稳定、有效控制地表沉降是目前地铁隧道施工中的一大技术难题.以重庆地铁三号线一段复杂地质段隧道开挖为例,针对开挖过程中出现地表路面沉降过大、构筑物开裂等问题,根据实际开挖过程建立隧道-土体-构筑物相互作用的三维有限元模型,对施工沉降产生的原因进行模拟对比分析和评价,在此基础上提出超前加固、及时支护等控制沉降的技术措施.监测结果显示采用改进技术措施后能有效控制拱顶下沉和地表沉降量,收敛值显著减小,说明改进施工方案达到了控制沉降、变形的目的.
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