隧道衬砌裂缝特征对承载力的影响分析

Analysis of the influence of tunnel lining cracks on bearing capacity

为明确松动荷载作用下,衬砌裂缝特征对结构承载性能的影响,通过1∶10模型试验和数值分析研究了带裂缝结构的受力变形特征、破坏模式和极限承载能力。结果表明:对于预制裂缝长度不超过L/3(试件纵向长度)、深度不超过0.7 H(试件厚度)的试件,裂缝发展存在阶段性特征,试件破坏由拱腰失效引起,属于延性破坏。对于预制裂缝长度不低于2 L/3或深度不低于0.9 H的试件,裂缝发展过程不存在阶段性特征,试件破坏由拱顶失效引起,属于脆性破坏;随裂缝长度和深度增加,结构极限承载力降低。当预制裂缝长度为L/3且深度为0.3 H、0.7 H、0.9 H,以及长度为2 L/3且深度为0.3 H、0.7 H时,试件极限承载力依次为完整试件的86.96%、78.26%、73.91%、69.57%、60.87%。相比于裂缝深度,纵向长度对结构承载性能影响更明显,可作为裂缝评价的重要指标;提出了基于裂缝特征的衬砌承载力预测公式,可明确带裂衬砌的极限承载力,为结构性能评估、加固时机及加固参数的选取提供依据。

In order to clarify the influence of crack characteristics on the bearing capacity of lining structures under loose load,the stress and deformation characteristics,failure modes and ultimate bearing capacity of structures with cracks were studied by 1∶10 model test and numerical analysis.The results show that:For specimens with prefabricated crack length less than L/3(longitudinal length of specimen)and depth less than 0.7 H(thickness of the specimen),the fracture development process is characterized by stages.The failure of specimens is caused by the failure of the vault and belongs to ductile failure.For the specimens with prefabricated crack length no less than 2 L/3 or depth no less than 0.9 H,there is no stage characteristics in the crack development process,and the failure of the specimens is caused by the failure of the vault,which belongs to the brittle failure.With the increase of crack length and depth,the structural ultimate bearing capacity decreases.When the length of prefabricated crack is L/3 and the depth is 0.3 H,0.7 H,0.9 H,and when the length is 2 L/3 and the depth is 0.3 H,0.7 H,the ultimate bearing capacity of the specimen is 86.96%,78.26%,73.91%,69.57%,60.87%of the complete specimen.Compared with the crack depth,the length has more obvious effect on the mechanical properties of the structure,and can be taken as an important index of fracture evaluation.A formula for calculating the bearing capacity of the lining based on the characteristics of cracks is proposed,which can be used to determine the ultimate bearing capacity of the lining with cracks,and provide a basis for the evaluation of structural performance,the selection of reinforcement timing and reinforcement parameters.