盾构隧道二次衬砌合理施作时机模型试验研究

Model tests on reasonable construction time of secondary lining of shield tunnel

近年来,盾构隧道双层衬砌作为一种新的形式开始得到应用推广,但由于相关研究较少,导致盾构隧道双层衬砌结构体系关键参数尚不明确,其中二次衬砌合理施作时机便是其中之一。以狮子洋隧道工程为依托,采用相似模型试验对二次衬砌合理施作时机展开研究,研究结果表明:二次衬砌在盾构隧道双层衬砌中仅作为辅助承载结构,施作时机为57%~83%,结构径向收敛值和椭圆度随加载步变化最为缓慢,结构累计声发射数AE呈渐进性增长;施作过早或过晚,二次衬砌均不能有效抑制管片衬砌变形,且结构累计声发射数AE均呈阶梯型增长;随着二次衬砌施作时机推迟,二次衬砌与管片衬砌最大内力量值之比及结构开始出现宏观损伤破坏荷载级别均呈先增大后减小的变化规律。因此,在综合考虑双层衬砌结构加载过程中的变形历程及损伤特性,认为二次衬砌合理施作时机为57%~83%。

Recently, the double-layer lining of shield tunnels has begun to be applied as a new form. However, due to the lack of the related researches, the key parameters of the double-layer lining structure system of shield tunnels are still unclear. The construction time of the second lining is one of them. Based on the Shiziyang Tunnel Project, a similar model test is used to study the reasonable construction time of the secondary lining. The results show that the secondary lining is only used as the auxiliary bearing structure in the double-layer lining of the shield tunnel. When the construction time is 57%~83%, the radial convergence and ellipticity of the structure change most slowly with the loading step, and the cumulative AE number of the structure increases progressively. If it is constructed too early or too late, the secondary lining can not effectively inhibit the deformation of the segment lining, and the cumulative AE number of the structure increases stepwisely. With the delay of the construction time of the secondary lining, the ratio of the maximum internal strength of the secondary lining to that of the segment lining and the load level of the macroscopic damage at the beginning of the structure both increase first and then decrease. Therefore, considering the deformation history and damage characteristics of the double-layer lining structure during the loading process, the reasonable construction time of the secondary lining is 57%~83%.