盾构隧道纵向接头抗拉性能试验

盾构隧道纵向在受到如地震、纵向地层变形等因素影响时，可能发生环缝张开，使得纵向接头在受拉时更容易破坏。为研究大断面盾构隧道纵向斜螺栓接头在拉拔过程中的受力变形特征及破坏过程，采用自主研制的接头螺栓拉拔装置，开展了1：1接头足尺抗拉性能试验，分析了管片纵向接头在不同加载方式及荷载工况下，管片混凝土应力分布、螺栓应力分布及传递、结构声发射信息和接头最终破坏模式等特征。研究结果表明：斜螺栓纵向接头在拉拔过程中会对管片纵向接缝面及外表面的应力分布产生影响，对管片内表面的应力分布影响较小；纵向斜螺栓在顺向拉拔过程中，未能充分发挥其承载能力，而在垂直接缝面的拉拔过程中，螺栓与套筒、管片内部混凝土的破坏基本保持同步，可充分发挥其承载能力，与混凝土强度配合较好；螺栓拧进套筒的程度影响纵向接头的抗拉拔能力，拧进程度越大，螺栓与套筒的联结能力越强，越能发挥纵向接头的抗拉拔能力；结构最终破坏模式是螺栓、套筒及混凝土间的联结失效，破坏具有突发性，顺拔工况下，纵向接缝面会在孔口周围发生近外表面的锥体破坏，垂直拔工况下，套筒内部螺纹被挤压破坏，因此，可采取提高套筒强度、加强套筒周围配筋等措施以进一步改善纵向接头的整体性能。

Pull-out Test of Longitudinal Joints of Shield Tunnel

When a shield tunnel is subjected to earthquakes and longitudinal stratum deformation, an annular gap may open along the longitudinal direction of the tunnel, rendering the longitudinal joint more vulnerable when being pulled. A self-made loading device was adapted to study the mechanical characteristics and the failure process of the oblique bolt of the longitudinal joint of a large-section shield tunnel in the drawing process. The tensile performance test of a 1:1 joint was conducted to study the mechanical characteristics of the longitudinal joint, including concrete stress distribution, bolt stress distribution and transmission, structural acoustic emission of the segment concrete, and the final failure mode of the longitudinal joint under different load conditions. The results show that during the drawing process, the longitudinal joint with an oblique bolt affects the stress distribution on the longitudinal joint surface and the outer surface of the segment, but has little effect on the inner surface of the segment. The bearing capacity of the longitudinal oblique bolt cannot be fully exerted in the drawing process along the forward direction. However, in the drawing process along the vertical joint surface, the bolts and the damage of the concrete inside the sleeve and the segment are synchronized, and the bolts can be fully exerted and match well with the strength of the concrete. The extent of screwing of the bolt into the sleeve affects the pull-out resistance of the longitudinal joint. The connection between the bolt and the sleeve and the anti-drawing ability of the joint are enhanced by the greater extent of screwing. The final failure mode of the structure occurs when the connection between the bolt, sleeve, and concrete fails, and this failure may happen suddenly. Under the condition of straightening, the conical damage around the orifice near the outer surface occurs on the longitudinal joint surface. Under the condition of vertical pulling, the thread inside the sleeve is destroyed by crushing. Therefore, the entire performance of the longitudinal joint can be further improved by enhancing the sleeve strength, enhancing the reinforcement around the sleeve, and so on.