粉细砂地层隧道涌水涌砂灾害模型试验研究

Model Test of Tunnel Water and Sand Inrush Disaster in Silty Fine Sand Stratum

近年来盾构在一些大埋深高水压砂层、砂卵石地层掘进时,因隧道内涌水涌砂而诱导的地层坍塌事故时有发生,因此亟需进一步探究隧道涌水涌砂的成灾机理与地层坍塌的破坏过程,为类似工程提供施工指导。基于已有工程案例,设计了隧道涌水涌砂可视化试验装置,研究了水土流失质量和土层横向破坏形态随时间的变化规律,并探讨了粉细砂密实度、模型隧道埋深、地下水位和漏点位置四种因素对隧道涌水涌砂灾害的影响。试验结果表明:盾构隧道涌水涌砂灾害可大致分为三个阶段,即漏水漏砂阶段、快速涌砂阶段和突水破坏阶段,可采用流失水土干物质比作为判别隧道涌水涌砂灾害发展阶段的依据;漏点位置和地下水位对地层渗透破坏的演化过程影响较大;粉细砂密实度越小、隧道埋深越浅、地下水位距地面越近且漏点位于隧道下方时,隧道涌水涌砂灾害发展越剧烈,水土流失质量越大。建议盾构在大埋深富水地层掘进过程中,做好地层加固方案,同时加强隧道,尤其是隧道拱底位置处的防水能力。

In recent years,when shield is tunneling in some large buried-depth and high water pressure sand layers and sandy gravel layers,stratum collapse accidents induced by tunnel water and sand inrush have been reoccurring.Therefore,it is urgent to further explore the disaster mechanism of tunnel water and sand inrush and the damage process of stratum collapse,providing construction guidance for similar projects.Based on existing engineering cases,a visual test device for tunnel water and sand gushing is designed to study the evolution law of soil and water loss quality and seepage damage of stratum.Besides,the influence of compactness of silty fine sand,buried depth of model tunnel,groundwater level and leakage point position are also discussed.The experimental results show that:(1)The disaster can be roughly divided into three stages:water and sand leakage stage,rapid sand gushing stage and water inrush damage stage.What′s more,the dry matter ratio of soil and water loss parameter is proposed as the basis for judging the development stage of tunnel water and sand inrush disaster;(2)The leakage location and groundwater level have great influence on the evolution process of formation seepage failure;(3)It is found that when the leakage spot is below the tunnel,the water and sand inrush disaster is more severe with a smaller silty sand compactness,a shallower tunnel buried depth and a higher water level height,and the water and soil loss mass is greater.It is recommended that during the excavation process of shield tunneling in large buried-depth water rich strata,a good ground reinforcement plan be made,while strengthening the waterproof capacity of the tunnel,especially at the arch bottom of the tunnel.