软土地区地面堆载对盾构隧道变形的影响分析

Influences of surface surcharge on the deformation of shield tunnel in soft ground area

针对上海小涞港河道填土工程,建立三维有限元模型来分析地面堆载对盾构隧道的影响,并将有限元计算结果与实测值对比。发现与采用MC本构模型相比,土体采用HSS本构模型时有限元计算结果与实测值吻合地更好,隧道的沉降曲线与实测基本一致。依托天津滨海地铁Z2线工程,分析堆载作用下不同因素对隧道变形的影响。结果表明当堆载中心不在隧道正上方时,隧道除竖向变形外,还会产生与堆载远离的水平位移;隧道埋深越浅,堆载中心与隧道轴线间的距离越近,地面堆载对既有隧道的影响越为显著;提高隧道周围土体刚度能显著降低堆载下盾构隧道的变形,因此软土地区通过加固土体可以有效减小地面堆载对既有隧道的影响。

According to the backfilling project on Xiao-lai-gang river way in Shanghai,the finite element model is established to analyze the influence of surface surcharge on shield tunnel,and the calculated results are compared with the measured data.It is found that when the soil adopts HSS mode,the calculated results achieves better agreement with the practical project than adopt MC model,and the settlement curve obtained by HSS model is basically consistent with the measured curve.Meanwhile,basing on subway line Z2 project in Tianjin,the influence of different factors on the deformation of shield tunnel under surface surcharge has been analyzed.The results show that when the center of surcharge is not just above the tunnel,the tunnel will produce horizontal displacement against the surface load besides vertical displacement.When the tunnel depth is shallower and the distance between surface loads and tunnel is shorter,the influence of surface surcharge on exist tunnel is more severe.Increasing the stiffness of the soil around the tunnel can significantly reduce the deformation of the shield tunnel under surface surcharge,therefore,reinforcing soil is an effective way to reduce the impact of ground loading on the existing tunnel in soft ground area.