天津软土地区盾构掘进对上方建筑物影响分析

Influences on surface structure induced by shield tunneling in Tianjin soft ground area

以天津地铁2号线下穿多层建筑物的盾构隧道为例,建立了盾构下穿空旷场地以及下穿建筑物的有限元模型,计算结果与现场实测数据进行了对比验证。在此基础上分析了在天津软土地区盾构隧道施工对地表沉降及多层砌体结构建筑物差异沉降的影响,并对采用小应变土体本构模型与硬化土本构模型的计算结果进行比较。结果表明,采用小应变本构模型的地表最大沉降和横向沉降槽宽度与实测数据吻合良好。盾构斜下穿砌体结构房屋时,建筑物有偏向隧道轴线方向的倾斜,采用小应变土体本构模型的计算结果可以更好地反映建筑物的倾斜斜率的变化。因此,研究软土地区盾构掘进对上方建筑物沉降影响的精细化分析时应考虑土体小应变的影响。

According to the construction of Tianjin Metro Line 2 passing under a masonry building, the finite element model is established to analyze the influence of tunneling on the ground surface and the surface masonry buildings. The calculated results which adopt the small-strain constitutive model are compared with the field measured data. The results are also compared with the conclusions obtained by the hardening soil constitutive model. The further analysis shows that both the maximum settlement and the width of traverse settlement trough predicted by small-strain model achieved better agreement with the practical project. And both the maximum settlement and the width of traverse settlement trough obtained by the hardening soil model are larger than the results obtained by the small-strain constitutive model. During the tunnel construction, the masonry building tilts to the axis of the tunnel.The rate of inclination obtained by the small-strain model can also consistent with the field data. Therefore, the small strain response of soil should be taken into account during the settlement investigation of buildings and ground surface induced by shield tunneling.