道床-管片界面黏结对隧道变形影响

Influence of interface bonding between invert-filling and segments on tunnel deformation

为研究道床对盾构隧道变形的影响,建立包含管片、钢筋笼、螺栓等结构的错缝拼装三维盾构隧道有限元模型,并采用足尺试验结果对模型的正确性进行验证。在隧道模型中加入道床结构并采用零厚度黏结单元模拟道床-管片界面,分析超载作用下道床脱空的过程及道床-管片界面的黏结牵拉作用对盾构隧道变形及管片内力、损伤的影响。研究结果表明:超载作用下,道床脱空最先发生于道床的边缘,随着水平收敛变形的增大,道床脱空的边界基本以平行的方式向拱底发展。道床脱空前,隧道水平收敛变形随荷载线性增长;随着道床脱空的发展,收敛变形快速增加,至脱空基本结束后,收敛变形增速放缓;界面的黏结不影响管片内力的分布顺序,但影响管片弯矩及偏心距的发展规律,脱空前道床边缘处管片具有更高的弯矩及偏心距,当发生脱空后道床边缘处管片弯矩及偏心距快速减小,其他截面管片弯矩及偏心距增加;由于道床-管片界面的黏结作用,在隧道变形过程中道床边缘处管片首先产生受拉裂缝,相同收敛变形下,隧道拱底处管片损伤区域更小,但损伤程度较深,拱底产生贯通裂缝的风险更高。一定程度上,道床对管片的牵拉作用会减小隧道的水平收敛变形。

In order to study the influence of invert-filling on shield tunnel deformation, a 3D finite element model of staggered shield tunnel including segments, rebars and bolts was established in this paper. The full-scale tests were used to verify the correctness of the model. The invert-filling was added to the tunnel model, and the cohesive elements were used to simulate the interface between invert-filling and segments. The process of invert-filling disengaging and influence of the invert-filling-segment bonding interface on the deformation of the shield tunnel and the internal force and damage of the segments under overload was analyzed. The results are drawn as follows. Under the overload, the invert-filling disengaging first occurs at the edge of the invert-filling. With the increase of horizontal convergence deformation, the boundary of disengaging basically develops to the arch bottom in a parallel manner. Before the disengaging, the horizontal convergent deformation of the tunnel increases linearly with the load. With the development of the invert-filling disengaging, the deformation of the tunnel increases rapidly. After the disengaging basically ends, the growth rate of the deformation slows down.The bonding of interface does not affect the distribution sequence of the internal forces of the segments, but affects the development of the bending moment and eccentricity of the segments. The segments at the edge of the invert-filling have higher bending moment and eccentricity before disengaging. When disengaging occurs, the bending moment and eccentricity decrease rapidly, and the bending moment and eccentricity of segments at other sections increase. Due to the bonding of interface, the segments at the edge of the invert-filling first produce tensile cracks in the process of tunnel deformation. Under the same convergence deformation, the damage area of the tunnel arch bottom segment is smaller, but the damage degree is deeper, and the risk of through cracks at the arch bottom is higher. To a certain extent, the pulling effect of the invert-filling on the segment will reduce the horizontal convergence deformation of the tunnel.