The construction-induced upfloating of shield tunnel on South Changsha Railway Station-Guangda Station Section of Changsha Metro Line No. 4 needs to be rehabilitated. As a result, the replacing technology of defective shield tunnel segment by composite lining is proposed according to the environment and geological conditions. (1) After route fitting by measured data, the defective shield tunnel length is about 40 m, and segment should be replaced reaches 25 (from ring 223 to 247). (2) The replacing technology of defective shield tunnel segment by composite lining is the best choice according comparison results among different replacing technologies by fuzzy comprehensive evaluation method.(3) The displacement and stress variation of ground and segment is studied by finite element method when dismantling ring by ring; and the results show bad situations, i. e., increase of vertical displacement crown top of surrounding rock, connected plastic zones of crown top of surrounding rock, increase of vertical displacement toward tunnel inside and horizontal displacement toward tunnel outside at segment adjacent to ring 1, compression of segment and increase of bending moment and axial force of segment, etc; which indicates that the segment dismantling number should be strictly controlled. (4) A new kind of movable trolley and its relevant construction technologies are developed and put into application to guarantee the safety of the tunnel structure and rapid construction.%为解决由于施工原因导致的区间右线盾构隧道严重上浮事故,文章依托长沙地铁4号线长沙火车南站-光达站区间工程,根据事故隧道所处环境及地质条件,提出在软岩地层中利用复合式衬砌置换缺陷盾构隧道管片的处理方法,主要内容: 1) 根据实测数据对线路进行拟合,确定缺陷盾构隧道的长度约为40 m,需处理管片为223 ～ 247环,共计25环管片;2) 采用模糊综合评价法对缺陷盾构隧道处置方案进行比选,结果表明在软岩地层中采用复合式衬砌全断面置换缺陷盾构隧道管片方案为最优方案;3) 采用有限元法分别研究单次拆除1环、2环、3环、4环管片时地层及管片的位移及应力变化,结果显示随着一次拆除管片环数的增加,围岩拱顶竖向位移逐渐增大并出现连通的塑性区,邻近第1环管片向隧道内竖向位移及向隧道外水平位移逐渐增大,管片逐渐被压扁,其弯矩、轴力值也逐渐增加,围岩及拆除区域附近管片结构体系越来越不安全,因此施工时需控制一次拆除管片的数量;4) 为确保管片置换时原盾构隧道结构体系的稳定,确保安全,做到快速施工,开发了一种新型台车及其施工方法,将其应用于实际工程.
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