地面堆载作用下盾构隧道结构变形分析

影响地铁盾构隧道结构安全的因素有很多,诸如周边基坑工程施工、土体不均匀性、流塑性软土空间分布状态、地面堆载等,其中以地面堆载诱发的隧道安全事故屡见不鲜。因此,探究地面堆载对隧道结构变形的影响规律,对规避安全隐患具有重要意义。以苏州地铁某线某区间盾构隧道为工程实例,利用ABAQUS数值分析软件,采用地层结构法建立隧道三维模型,系统地分析了不同堆载位置下盾构隧道的变形规律。结果表明：地面堆载作用下,隧道变形沿隧道走向呈对称分布,隧道结构变形量随堆载大小的增加逐渐增大,随堆载偏离隧道外边线距离的增加而逐渐减小；当堆载的偏移距离为三倍隧道直径时,隧道竖向位移发生由下向上的方向转变,水平位移发生由右向左的方向转变；隧道正上方的地面堆载导致隧道变形过大,影响隧道安全使用,偏压堆载下隧道变形显著减小,其变形量满足规范要求,隧道处于安全状态。

Deformation Analysis of Shield Tunnel Structure under Ground Loading

There are many factors affecting the structural safety of subway shield tunnels, such as the construction of surrounding foundation pits, soil heterogeneity, spatial distribution of fluid plastic soft soil, and ground loading, etc. Among them, tunnel safety accidents induced by ground surcharge are common. Therefore, it is of great significance to explore the influence of ground surcharge on the deformation of tunnel structure to avoid safety hazards. Taking a shield tunnel in a certain section of Suzhou Metro as an engineering example, the numerical analysis software ABAQUS is used to establish a three-dimensional model of the tunnel by using the stratum-structure method, and the deformation law of the shield tunnel under different loading positions is systematically analyzed. The results show that under the action of ground surcharge, the tunnel deformation is symmetrically distributed along the longitudinal direction. The deformation of the tunnel structure increases with the increase of the stacking load, and decreases with the increase of the distance from the surcharge load to the outer edge of the tunnel. When the offset distance of the ground surcharge is three times the tunnel diameter, the vertical displacement direction of the tunnel changes from downward to upward, and the horizontal displacement changes from right to left. The ground loading above the tunnel leads to excessive deformation of the tunnel, which affects the safe use of the tunnel. The deformation of the tunnel under the bias surcharge load decreases significantly, and its deformation meets the requirements of the specification, and the tunnel is in a safe state.