管幕作用下矩形大断面开挖面稳定模型试验研究

Model experiment study on stability mechanisms of large rectangular excavation faces under the effect of pipe roof

管幕箱涵工法因其施工过程环境扰动较小的特性非常适合建设下穿通道。进行砂土地层中重力场非相似模型试验,探究管幕结构在维持开挖面稳定和限制环境扰动方面的作用,通过控制开挖面板位移模拟开挖面失稳破坏过程,采用压电薄膜监测开挖面三维土压力分布形式、DIC双目相机监测地表三维位移和分布式光纤监测模型管幕变形将传统监测从点拓展到线和面。对比分析开挖面荷载大小及分布、地表沉降大小及分布和管幕结构变形随开挖面位移变化规律,揭示管幕作用下矩形开挖面稳定及环境影响机制。管幕结构能够阻断滑动面向地表延伸及滑动块上方土体塌落,最终承担部分松动土压力并维持上覆土中土拱结构稳定,有效降低矩形开挖面荷载并显著限制环境扰动。模型试验研究结论对管幕箱涵工法发展具有指导意义。

The roof box jacking(RBJ)method is very suitable for the construction of the underpass because of its micro-disturbance.The non-similar model experiment of the gravity field in sand layers is carried out to explore the role of the pipe roof in enhancing the stability of the excavation face and restricting the environmental disturbance.The instability process of the excavation face is simulated by controlling the displacement of the excavation face.Advanced monitoring technologies including piezoelectric film,DIC binocular camera and distributed fiber optic are adopted to respectively monitor three-dimensional earth pressure distributions of the excavation face,three-dimensional ground displacements and deformation of the pipe roof.The influence of the excavation face displacement on the load size and distribution of the excavation face,the size and distribution of the ground settlement and the deformation of the pipe roof is discussed,and the stability mechanism of the excavation face under the effect of the pipe roof is analyzed.It is found that the pipe roof can prevent the sliding surface from extending to the ground surface and the soil above the sliding block from collapsing.Simultaneously,the pipe roof bears part of the overburden pressure together with the soil arch,effectively reduces the load on the excavation face and significantly restricts the environmental disturbance.The conclusions of the study have guiding significance for the development of the roof box jacking method.