旁侧基坑开挖卸载工况下槽钢加固盾构管片的加固效果研究

Reinforcement Effect of U-Steel Reinforced Shield Segment Under Excavation Unloading of Side Foundation Pit

为解决日益增长的盾构隧道修复治理问题,丰富现有隧道管片的加固体系,针对已有的槽钢加固中的不足开展槽钢加固盾构管片截面的有限元研究,通过MIDAS GTS NX有限元软件建立精细三维管片模型,并将模拟结果与足尺试验结果对比验证,然后开展槽钢环数、拼装形式、加固形式等影响因素的研究,旨在更全面地认识旁侧基坑开挖卸载工况下槽钢加固管片的受力变形性能和加固效果。研究结果表明:1)4环槽钢加固可有效限制管片的收敛变形并减小螺栓主应力;2)错缝拼装形式下管片的顶底收敛变形和螺栓应力在槽钢加固前后均呈现小于通缝拼装管片的特点;3)槽钢最大主应力主要出现在顶部、腰部和200°~220°过渡段,可对这些部位采取局部加强措施;4)槽钢-钢板组合加固是一种可靠的加固方式,对管片顶底收敛变形的加固效果明显,最大加固效率可以达到45.8%且经济性良好。

The repair and governance of shield tunnels are widely common nowadays.Hence,it is essential to improve the reinforcement system of the tunnel segments.In this study,the deficiencies in the existing U-steel reinforcement are presented,and a finite element study of the cross-section of U-steel reinforced shield tunnel segment is conducted.The MIDAS GTS NX finite element software is employed to establish a fine three-dimensional segment model,and the simulation results are compared with the full-scale test results.In addition,the influencing factors,such as the number of U-steel rings,assembly form,and reinforcement form,are examined to investigate the mechanical deformation performance and reinforcement effect of U-steel reinforced segments under excavation unloading of the side foundation pit.The research results reveal the following:(1)The four-ring U-steel reinforcement minimizes the convergence deformation of segments and reduces the principal stress of bolts.(2)The top-bottom convergence deformation and bolt stress of the segment under the staggered seam assembly form are smaller than those of the through-seam assembly before and after U-steel reinforcement.(3)The maximum principal stress of U-steel is mainly located at the top,waist,and 200°~220°transition section and it can be strengthened locally.(4)The combination reinforcement of U-steel and steel plate is found to be a reliable reinforcement method that has significant reinforcement effect on the convergence deformation of the top and bottom of the segment.The maximum reinforcement efficiency can reach 45.8%with a good economic benefit.