盾构施工扰动对隧道结构弹性沉降的影响

Impact of Shield Tunnel Construction disturbance on Elastic Settlement of Tunnel Structure

为探索盾构施工扰动对隧道弹性沉降影响的估算方法，需估计隧道最终沉降。以某地铁为背景，基于Winkler弹性地基梁理论，同时考虑土的扰动程度，得到土体扰动度与隧道弹性沉降的关系；考虑隧道上覆荷载、土体初始变形模量及隧道弯曲刚度不同取值对隧道弹性沉降进行修正；然后基于某地铁8年的监测数据，半定性半定量地分析了扰动度、地质条件、上覆荷载对隧道沉降的影响，并考察了弹性沉降占总沉降的比例，及不同地质条件、上覆荷载情况下扰动度的分布范围。研究表明：隧道弹性沉降量与隧道上覆荷载成正比；与土体初始变形模量呈幂函数关系；与土体扰动度D呈指数关系；这3个因素相互关联，地质条件好、上覆荷载小的区域往往施工扰动小，地质条件很差、上覆荷载很大的区域往往施工扰动大；粗略估计，隧道弹性沉降约占总沉降量的20％；该地铁施工扰动度一般在0．2～0．5，地质条件较好且上覆荷载较小的地区，扰动度大概在0．2～0．3；对于地质条件较大且上覆荷载较大的区域，扰动度大概在0．4～0．5；选择上覆荷载较小、地质条件较好的地段，比较容易将扰动度D控制在较小的范围内，可明显减小对隧道弹性沉降及最终沉降。

The method for evaluation of elastic settlements of tunnel due to shield tunnel construction disturb- ances was explored, and the final settlements of tunnel were evaluated with a subway as the background. The relationship between the elastic settlement of tunnel and disturbance degrees of soil mass was found on the ba- sis of the Winkler Elastic Foundation Beam Theory and Disturbance State Concept. Then the elastic settle- ments of tunnel were modified corresponding to different sampling of the superimposed load, the initial deform-ation modulus of soil mass and the bending stiffness of tunnel. According to the 8-year monitored data of set- tlements of a subway, the impact of the disturbance degrees, geological conditions and superimposed loads on the settlements of tunnel was analyzed semi-qualitatively and semi-quantitatively, and the proportion of elastic settlements in total settlements and the distribution scopes of disturbance degrees under different geological conditions and different superimposed loads were investigated. The study show as follows： The elastic settle-ment of tunnel is directly proportional to the superimposed load of tunnel, and is of the power function relation- ship with the initial deformation modulus of soil mass and of the exponential relationship with D, the disturb-ance degree of soil mass~ when the bending stiffness of tunnel changes little, it has little effect on the modified elastic settlement of tunnel; the three mentioned factors are interrelated, i. e. , the disturbance degree is usual-ly small in the area with good geological conditions and small loads imposed on tunnel and the disturbance degree is usually large in the area with bad geological conditions and large loads imposed on tunnel; by a rough estimate, the elastic settlement of tunnel account for 20%o of the total settlements; Generally speaking, the dis-turbance degrees lie within the range of 0.2-0.5 for the subway, however, the disturbance degrees change to the range of 0.2-0.3 in the area with good geological condition and small loads imposed on tunnel, and to the range of 0.4-0.5 in the area with bad geological conditions and large loads imposed on tunnel.