封顶块位置对盾构隧道管片结构力学特征与破坏形态的影响分析

Analysis of mechanical characteristics and failure pattern of shield tunnel segment with different position of key block

对于盾构隧道管片衬砌结构而言,封顶块位置对其在相同荷载条件的力学响应及破坏失稳特征具有显著的影响,通过将渐进性破坏理论引入到盾构隧道管片衬砌结构病害发生及扩展过程分析中,采用相似模型试验研究方法,从盾构隧道管片的声发射数据、结构位移及内力、宏细观裂纹发生及扩展等方面,比较分析封顶块位置对盾构隧道管片从材料细观损伤到结构宏观局部破坏再到结构整体失稳的整个渐进性破坏失稳过程的影响。试验结果表明：1封顶块的位置不同,使得因环向接头的位置不同,在外荷载一样的情况下,管片与地层的协调变形不同,导致整环管片的整体刚度不同,封顶块位于拱腰时其整体刚度相对其他两组较大;2封顶块不同位置对结构失稳时的最大局部变形位置有较大影响,临界失稳时的最大位移与隧道半径之比相差不大,均在2%~3%之间;3封顶块不同位置对管片结构开始产生宏观裂缝的荷载级别及产生位置也有较大影响,封顶块位于拱腰时,开始产生宏观裂缝的荷载级别相对其他两组大,主裂缝和压溃区发生的位置较多。

For lining segments of shield tunnel under the same loading conditions,the position of key block may significantly affect the mechanical response and failure characteristic of lining structure.The progressive damage theory was firstly introduced into the disease occurrence and propagation analysis of shield tunnel segments,and a comparative study was carried out based on the similarity model test for the influence of different position of key block during the whole progressive failure process of lining segments.The acoustic emission data,displacement and internal force of lining segments as well as the crack occurrence and propagation in lining segments were analyzed comprehensively.Consequently,the results show that：1） The difference in position of key block may lead to the difference in position of hoop joint.Under the same external load,the coordinated deformations between the segments and the strata may be different so that the integral stiffness of the entire ring could be different.The integral stiffness for the case with key block located at haunch is larger than the other two cases.2） The difference in position of key block may significantly affect the position of the maximum local deformation.The ratios of the maximum displacement to the tunnel radiusat the critical buckling point do not change remarkably,and in fact,the range generally varies between 2% and 3%.3） The difference in position of key block may also have significant influence on the load levels at the occurrence of macro cracks as well as the locations of macro cracks.For the case with key block located at the haunch,the load level at the occurrence of macro cracks is larger than those for the other two cases,with much more major cracks and crushing zones.