偏压荷载下裂损特征对隧道衬砌受力影响试验

Experiment on the influence of cracking characteristics under unsymmetrical load on stresses or forces in tunnel lining

研制了偏压加载的全周封闭隧道模型试验装置，可对衬砌结构任意位置施加荷载，较真实地模拟偏压荷载作用下损伤衬砌受力特征。完成了6组1：10破坏性模型试验，对比偏压荷载下衬砌结构力学行为的裂缝特征效应。试验结果表明：偏压荷载下完整衬砌破坏过程为“偏压侧拱脚、非偏压侧拱肩、偏压侧拱肩”，共三个阶段，前三条裂缝出现时承载为极限荷载的30％-45％；压皱出现时承载比例为70％，试件急剧破坏，整体呈延性破坏。裂缝和荷载在同侧时，加载破坏过程为“偏压侧裂缝张开、压皱、试件破坏”，呈脆性破坏，拱肩裂缝对衬砌承载力影响最大。第一条预制裂缝在拱顶，深度为1／3衬砌厚度，第二条预制裂缝在拱肩，深度分别为1／3、1／2、2／3衬砌厚度时，试件极限荷载为完整衬砌的86．34％、76．09％、68．94％。衬砌结构均为偏压侧拱肩外侧压碎导致整个结构失去承载能力。损伤裂缝使得结构刚度大幅度减小，提出了裂缝深度与极限承载力关系公式，模型试验结果与公式计算值基本一致。

The loading device for highway tunnel model tests was manufactured. The device could load at any position of lining, and it can simulate the stress/force characteristics for cracking lining under unsymmetrical load. Six model tests of 1：10 were carried out to compare the effect of crack in lining under unsymmetrical load. Test results show that for intact lining, the damage process is composed of three phases： arch-springing collapse under the bias load, spandrel collapse under the non-biased load and under the bias load. Before the occurrence of the first three cracks, the bearing capacity is bout 30% -45% of the ultimate load. The load proportion is about 70% when crumpling occurs, and at that moment the specimen collapses sharply, characterized with the global ductile failure. When the crack and unsymmetrical load are located at the same side of the specimen, the damage process appears to be the crack expansion under the bias load, crumpling and collapse of specimen, characterized with the brittle failure and the most significant influence of spandrel cracking on the bearing capacity of lining. It is found that the first crack appears at the arch with the depth as 1/2 of lining thickness, the second crack occurs at the spandrel with 1/3, 1/2 and 2/3 of lining thickness, respectively, and the corresponding ultimate load is 86.34%, 76.09% and 68.94% of that of intact lining. In addition, crushing may occur at the external surface of lining, which leads to the loss of the entire capacity of lining. The damage crack lead to the sharp decline of structural stiffness. Furthermore, the relationship formula between crack depths and ultimate bearing capacities is proposed, and results show that the model test agrees well with the prediction of the formula.