并行盾构隧道扩建车站Y形节点力学性能试验研究

Experimental study on mechanical behavior of Y-joints in subway station structure by expansion of parallel shield tunnels

在并行盾构隧道基础上扩建的地铁车站结构中,处于装配式的盾构管片和现浇车站主体结构之间的Y形节点是车站结构受力的薄弱位置,为研究Y形节点的力学性能和失效破坏机理,该文进行了Y形节点1∶1足尺试验,并分别对两种不同类型的节点在双向荷载作用下的混凝土应变、钢筋应变、节点破坏现象以及节点的失效破坏机理进行了分析。结果表明,钢板上焊接抗剪键可有效增强节点的抗剪性能,但由于抗剪键对管片下部混凝土有较强的约束作用,导致管片刚度上下差异较大,节点抵抗外力的能力大大降低;两类节点的破坏机理不同,A类节点破坏主要是由于管片底部混凝土被压碎剥落所导致,属于混凝土受压破坏;B类节点其破坏主要是由于管片上部受拉开裂所导致,属于混凝土的受拉破坏。两类节点试件都可满足扩挖车站结构中Y形节点的强度和变形方面的要求。除此之外,该文进一步提出了提高节点受力性能的改进措施。

The Y-joints between prefabricated shield tunnel lining segment and cast-in-place main structure of station are the mechanical weaknesses of the station structure by expansion of parallel shield tunnels.The static tests on Y-joints of 1∶1 scale were conducted to study the mechanical behavior and failure mechanism of the joints.The concrete strain,steel strain,damage pattern and damage mechanism of two types of Y-joints were studied under the horizontal and vertical loads.The results showed that the shear capacity of Y-joints can be strengthened with the shear key wielded on the steel plate.The shear key,however,has a strong restraint effect on the lower part concrete of the lining segment.As a result,the lining segment stiffnesses of upper and lower part differ greatly,and the ability of the joint in resisting external forces is greatly reduced.The failure mechanisms of the two types of Y-joints are different.The failure of the joint of type A is mainly caused by the crushing of concrete at the lower part of the segment which shall be the compression failure of concrete.The failure of the joint of type B is mainly caused by the tensile cracking of the upper part of the segment concrete which shall be the tensile failure of concrete.Both the two types of Y-joints in this test can meet the requirements of strength and deformation of the station structure by expansion of parallel shield tunnels.Furthermore,some measures for the Y-joint are put forward here to improve the mechanical performance of the structure.