纯压弯受力下大断面盾构隧道管片接头抗弯足尺试验研究

Full-scale Experimental Study on Bending Performance of Segmental Joints of Large Cross-section Shield Tunnel under Pure Compressive Bending Condition

针对管片接头抗弯试验中接头是否处于纯压弯受力状态影响试验结果准确性问题,设计一套可使接头具有较大转动角度、保证其处于纯压弯受力状态的抗弯加载装置,并开展一系列不同轴力和弯矩下接头抗弯性能试验,试验中采用差动式位移计和应变传感器等对接头变形和螺栓应变进行测量。基于试验结果得出:1)接头处于纯压弯受力状态时,正负弯矩下管片接头竖向位移、张开量、闭合量、转角、螺栓应力随弯矩变化的曲线较为平顺;2)正弯矩下接头张开高度随弯矩变化可分为2个变化阶段,而负弯矩下受接缝面复杂变形接触关系影响,在上述2阶段变化规律之间出现了明显的"平台段";3)接头采用斜螺栓连接时,正弯矩下轴力对接头的抗弯性能影响大于负弯矩下轴力对接头的抗弯性能影响,且正负弯矩下抗弯性能的差异随着轴力的增大而减小。

In the full-scale compressive bending test of segmental joint,whether the joint is in a state of pure compressive bending is one of the most important factors affecting the accuracy of test results.Hence,a loading device for bending test of segmental joint with large rotation angle and in a state of pure compressive bending is designed.A series of bending tests for segmental joint under different axial forces and moments are carried out.The LVDTs and strain gauges are adopted to measure the joint deformation and bolt strain.Based on the test results,the conclusions are drawn as follows:(1)When the joint is in a state of pure compressive bending,the variation curves of vertical displacement,opening,closure,rotation angle,bolt stress with bending moment under positive and negative moments are relatively smooth.(2)The variation of the opening height of joint with bending moment under positive moment can be divided into two stages,while an obvious"platform section"appears between the above-mentioned two stages under negative moment due to the influence of complex deformation contact relationship of the joint surface.(3)When the joints are connected by oblique bolt,the axial force has a greater impact on the bending performance of the joint under positive moment than that under negative moment,and the bending performance differences of the segmental joint under positive and negative moments reduce with the increase of axial force.