沉管隧道地基砂流法处理的砂盘扩展规律试验与分析

EXPERIMENT AND ANALYSIS OF LAW OF SAND DEPOSIT EXPANSION IN FOUNDATION OF IMMERSED TUBE TUNNEL TREATED BY SAND FLOW METHOD

为探索沉管隧道砂流法地基处理过程中砂盘扩展的规律,建造砂流法足尺试验模型,并针对砂盘实时探测的困难自制砂盘探测器,通过8次试验得到砂盘形状及其扩展尺寸在不同试验条件下随时间的变化关系。分析表明:砂颗粒在喷口周围呈环状沉积并逐步形成冲积坑和砂盘;砂盘顶部形成流缝和流槽,基本沿砂盘径向延伸,周向随机分布;砂颗粒从流缝和流槽中带出并堆积于砂盘外缘面上形成斜层状纹理结构。砂水比、边界条件、基槽间隙和板底粗糙度主要对砂盘扩展过程产生影响,而对砂盘的最终尺寸及密实度的影响并不显著。该试验结果可为洲头咀沉管隧道地基处理提供有价值的设计与施工依据及建议。

In order to explore the law of sand deposit expansion in the sand foundation treatment process treated by sand flow method in the immersed tube tunnel engineering, full-scale test model was built and sand-deposit detector was developed. Changes of sand deposit shape and sand deposit expansion size with time under different experimental conditions were obtained through eight experiments. The analysis result shows that sand grains deposit around the vent in ring-shaped and form crater and sand deposit gradually. Gap and chute for flow form on the top of the sand deposit, elongating basically along the radial direction and distributing randomly on circumferential direction. Sand grains are carried from the gap and chute and deposit on the outer margin surface of the sand deposit, in which oblique layered texture is formed. The factors such as the mass ratio of sand-water, the boundary conditions, the foundation trench and the roughness of the model board have a major impact on the expansion process of the sand deposit but not significantly impact the final size and the density. The test results may be help to design and construction of the Zhoutouzui immersed tube tunnel in Guangzhou.