上软下硬地层大直径泥水盾构施工土体变形研究

Study on soil deformation of large diameter slurry shield construction in upper soft and lower hard stratum

大直径盾构在穿越上软下硬地层时容易发生姿态失稳,产生超挖现象,引起的地表沉降,威胁周围建筑物的安全。以环城北路-天目山路提升改造工程为背景,建立大直径盾构隧道模型,基于地表沉降数值结果和现场监测值,分析大直径泥水盾构在上软下硬地层中施工对周围土体变形的影响。研究结果表明:1)邻线隧道施工造成地表沉降明显存在相互影响作用,先行线掘进会引起后行线开挖面前方土体沉降;2)掌子面压力增大时,盾构前方地表沉降减小,而最终地表沉降增加;3)受上软下硬地层影响,施工参数对盾构机下方土体基本没有影响;4)增加注浆压力对控制地表沉降非常有限;5)施工中掌子面压力取400kN/m^(2)左右比较合理,且需及时进行二次注浆。

When the large-diameter shield passes through the upper soft and lower hard strata, it is easy to lose its posture,resulting in over-excavation, resulting in surface settlement, threatening the safety of surrounding buildings. Taking the Huancheng North Road Tianmushan road upgrading and reconstruction project as the background, a large-diameter shield tunnel model is established. Based on the numerical results of surface settlement and field monitoring values, the impact of large-diameter slurry shield construction in the upper soft and lower hard strata on the surrounding soil deformation is analyzed.The results show that: 1) there is an obvious interaction between the surface settlement caused by the adjacent line tunnel construction, and the advance line excavation will cause the soil settlement in front of the later line excavation face;2) When the tunnel face pressure increases, the ground settlement in front of the shield decreases, while the final ground settlement increases;3) Affected by the upper soft and lower hard stratum, the construction parameters have little effect on the soil under the shield machine;4) Increasing grouting pressure is very limited to control surface settlement;5) It is reasonable to take the tunnel face pressure of about 400kn/m~2 during construction, and secondary grouting shall be carried out in time.