盾构法联络通道中提高切削效率的管片弱化研究

Study on Weakening Measures to Improve Cutting Efficiency of Temporary Segment in Shield Tunnel Construction

盾构法联络通道施工中因洞口处临时管片难以切削,施工中存在掘进周期长、盾机姿态难控制、涌水涌砂风险高等问题,但是关于此问题解决方案的研究目前还很缺乏。因此,本文以天津某地铁盾构法联络通道项目为背景,在保证结构施工及使用期间安全性的基础上,从弱化临时管片的角度出发,提出了3种弱化方式,分别为降低待切管片砼强度等级、减少玻璃纤维筋布筋量以及管片打孔,并利用有限元数值模拟对弱化的可能性及影响进行了研究。结果表明:(1)在3种弱化方式下,特殊衬砌环内力变化规律均为切削区内力减小,钢管片区内力增大,普通衬砌环的内力小幅度提高;(2)临时管片砼强度由C40降到C20后对衬砌环内力影响在15%以内,其中钢管片区内力增加量在5%以内;(3)主筋量减少70%以内对管片内力影响在2%以内;(4)管片内侧打孔使切削区弯矩降低30%左右,孔径与孔深尺寸相同变化量情况下,孔径对于内力影响大于孔深;(5)不同弱化方式弱化后的结构内力均在极限承载范围之内,3种弱化方式均可采用,从施工便利性和安全性角度来看,临时管片砼强度降低方案为最优方案。

Due to the difficulty of cutting the temporary segment at the mouth of the tunnel in the construction of shield tunneling method,there are some problems in the construction,such as long tunneling period,difficult to control the attitude of shield machine,and high risk of water and sand gushing.However,there is still a lack of research on the solutions to these problems.Therefore,based on the background of the shield tunnel project of a subway in Tianjin,on the basis of ensuring the safety of the structure during construction and use,this paper proposes three weakening methods from the perspective of weakening the temporary segment,which are to reduce the concrete strength grade of the segment to be cut,reduce the amount of glass fiber reinforcement and drilling the segment.The possibility and influence of weakening were studied by finite element numerical simulation.The results show that:(1)Under the three weakening methods,the internal forces of the special lining ring are decreased in the cutting area,the internal forces of the steel tube area are increased,and the internal forces of the ordinary lining ring are slightly increased.(2)After the temporary segment concrete strength is reduced from C40 to C20,the internal force of the lining ring is affected within 15%,and the internal force of the steel pipe area is increased within 5%.(3)the influence of the main reinforcement amount on the internal force of the segment within 2%is less than 70%.(4)Drilling inside the segment reduces the bending moment of the cutting area by about 30%.Under the same variation of the size of the aperture and the hole depth,the influence of the aperture on the internal force is greater than the hole depth.(5)The structural internal forces weakened by different weakening methods are all within the limit bearing range,and all the three weakening methods can be adopted.From the perspective of construction convenience and safety,the concrete strength reduction scheme of temporary segment is the optimal scheme.