纵向力作用下的盾构隧道管片结构纵向弯曲变形性能研究

STUDY ON LONGITUDINAL BENDING DEFORMATION BEHAVIOR OF SHIELD TUNNEL SEGMENTS REGARDING THE ACTION OF LONGITUDINAL FORCE

为探明盾构隧道在纵向力作用下的纵向弯曲变形性能,以武汉两湖隧道工程(东湖段)为背景开展了管片结构纵向模型试验,对隧道的竖向位移与纵向应变进行了研究,探明了纵向力对盾构隧道纵向弯曲变形性能的影响。研究结果表明:纵向力能够提高隧道的纵向抗弯刚度,其对纵向抗弯刚度的提升作用随竖向荷载的增加呈先增大后减小的趋势。以竖向荷载分别为3200 kN、9600 kN、16000 kN为例,当隧道从无纵向力作用到竖纵荷载比K分别为0.56、1.67、2.78时,隧道的最大竖向位移分别减少了45.5%、56.8%、62.7%,而竖向荷载为22400 kN、K为3.89时仅减小了23.5%。管片结构纵向刚度有效率随竖向荷载的增加而减小,根据减小的程度可分为3个阶段:第一阶段为刚度弱化阶段;第二阶段为刚度稳定阶段;第三阶段恢复至刚度弱化阶段。纵向刚度有效率同时受竖向荷载与纵向力共同的影响,且当竖向荷载一定时,竖纵荷载比越小,隧道的纵向刚度有效率越大,当竖向荷载为22400 kN、竖纵荷载比K从35减小至3.89时,隧道的纵向刚度有效率减小了16.2%。以跨中横截面为例,隧道横截面的中性轴在竖向荷载的作用下会随着隧道的变形而上移,增加纵向力能使中性轴下移并趋近于拱腰位置。该文试验所得纵向刚度有效率在无纵向力时与现有模型试验结果相近,在考虑纵向力后大于现有研究结果,纵向刚度有效率应考虑残余纵向力的影响,建议取值为0.218~0.696。

To investigate the longitudinal mechanical behavior of shield tunnels under the action of longitudinal forces,a longitudinal model test of a segment of the tunnel structure was carried out based on Wuhan Lianghu Tunnel(Donghu section).The vertical displacement and longitudinal strain of the tunnel are analyzed to reveal the influence of the longitudinal force on the longitudinal mechanical behavior of shield tunnels.The results show that:The longitudinal force can improve the longitudinal bending stiffness of shield tunnels,but the effect of the longitudinal force on the longitudinal bending stiffness increases first and then decreases with the increase of the vertical load.Taking the vertical loads of 3200 kN、9600 kN and 16000 kN as an example,the maximum vertical displacement of the tunnel decreases by 45.5%,56.8%and 62.7%respectively,when the vertical and longitudinal load ratio K is 0.56、1.67、2.78 respectively,but only decreases by 23.5%when the vertical load is 22400 kN and K is 3.89.The longitudinal bending stiffness efficiency of the segment structure decreases with the increase of vertical load,which can be divided into three stages according to the reduction degree:The first stage is stiffness weakening,and the second stage is stiffness stabilizing,the third stage restores to the stage of stiffness weakening.Longitudinal bending stiffness efficiency is affected by both vertical load and longitudinal force.When the vertical load is constant,the smaller K is,the greater the longitudinal bending stiffness efficiency is.When the vertical load is 22400 kN and K is reduced from 35 to 3.89,the longitudinal bending stiffness efficiency of shield tunnels decreases by 16.2%.Taking the midspan cross-section as an example,the neutral axis moves up with the deformation of the tunnel under the action of vertical load.Increasing longitudinal force can make the neutral axis move down and reach the position of the arch waist.The longitudinal bending stiffness efficiency obtained in this test is similar to the existing model test results in the absence of longitudinal force,but greater than the existing research results after considering the longitudinal force.The longitudinal bending stiffness efficiency should be considered with the influence of residual longitudinal force.and the recommended value is 0.218~0.696.