裂缝数量对盾构隧道管片结构力学性能的影响

盾构隧道管片在制作、养护、运输及拼装过程中，常会出现裂缝，裂缝的存在在一定程度上会影响管片衬砌结构的整体受力。以中国某地铁越江盾构隧道为工程背景，采用相似模型试验的方法，基于盾构隧道管片的位移、内力及声发射数据，系统分析裂缝数量对管片衬砌结构力学特性的影响规律，并通过管片破坏过程示意图分析管片结构的破坏模式。研究结果表明：管片衬砌结构承载阶段可划分为弹性承载、塑性承载和破坏失稳3个阶段；裂缝的存在降低了管片衬砌结构的整体刚度，随裂缝数量增加，管片衬砌结构的弹性承载范围增加，塑性承载阶段范围减小，损伤破坏的空间影响范围呈增大趋势，结构的失稳破坏趋于突发性破坏，相同荷载下的变形增大，结构的极限承载力降低；裂缝的存在使得管片在预制裂缝位置产生纵向贯通裂缝，随裂缝数量增加，纵向贯通裂缝数量增加，破坏区域由某一位置发展为条带状分布，当拱腰预制裂缝数量达到3条时，裂缝之间管片的相互挤压导致网状裂缝产生，结构局部出现压溃区。

Influence of Crack Number on Mechanical Properties of Shield Tunnel Segment Structure

Cracks often develop in the process of producing, maintaining, transporting, and assembling shield tunnel segments, and the overall stress levels are affected by the existence of cracks to some extent. Considering a cross-river shield tunnel project in China as an example, and based on the similarity model test, a systematic study of the influence of crack number on the mechanical properties of segment lining structures was conducted. Additionally, the failure mode of the segment structure was studied through the schematic diagram of failure process. The acoustic emission data, displacements, and internal forces of segment linings were measured and analyzed. The results show that the loading of the segment lining structure can be divided into three stages:elastic bearing stage, plastic bearing stage, and unstable failure stage. Owing to the existence of cracks, the overall load bearing capacity of the structure is reduced. With an increase in the number of cracks, the elastic bearing range of the lining structure increases, and the plastic bearing range decreases; the tendency for the spatial impact range of the damage increases and unstable failures are more sudden. Further, displacements under the same load conditions increase, and the ultimate bearing capacity of the structure reduces. The existence of cracks causes the segment to generate longitudinal through-cracks at the precast crack locations. As the number of cracks increases, the number of longitudinal through-cracks increases, and the damage area develops from a certain location to a banding distribution. This study shows that when the number of precast cracks on the hance of the tunnel reaches three, because the segments between cracks squeeze one another, reticulated cracks are generated, and crushing areas are formed at certain locations in the structure.