基于透明土的静压桩贯入特性的模型试验研究

Model tests on the penetration characteristics of jacked pile in transparent granular soil

为了探究不同桩型贯入过程的作用机理和挤土效应,进一步揭示“楔形体”现象,基于透明土可视化模型试验和优化的增量RG-PIV图像处理技术,采用小型试验机加载系统开展了平头桩和圆锥桩的静压贯入试验,并将试验结果与SSPM理论解进行了对比。利用高温染色技术对熔融石英颗粒进行染色处理,进而用染色的颗粒对透明土试样进行部分替换,形象而直观地观测到楔形体的形状和大小。在此基础上,分析了平头桩和圆锥桩贯入过程对周围土体扰动的模式。结果表明:平头桩贯入对周围土体的变形影响大于圆锥桩;由于未考虑桩土之间的摩擦,SSPM对于近桩侧的土体变形预测有一定的局限性;对于浅基础贯入问题,桩周土的变形主要表现为向上隆起;两种桩型不同贯入机理的主要原因是平头桩底部的楔形体效应。

In order to explore the penetration mechanism and the squeezing effect in sand for different pile types in the process of penetration, the phenomenon of wedge is further revealed. Based on the visualization test technology of transparent soil and incremental reliability-guided particle image velocimetry(RG-PIV), the static pressure penetration test of flat-ended pile and cone-ended pile are carried out with a small test machine loading system, and the test results are compared with the SSPM theoretical solution. At the same time, the fused quartz particles are dyed by high-temperature dying technology, and then the transparent soil samples are partially replaced with the dyed particles, so that the shape and size of the wedge could be observed visually. On this basis, the soil disturbance caused by penetration of flat-ended pile and cone-ended pile is analyzed. The resulting data illustrates that the effect of flat-ended pile penetration on surrounding soil deformation is greater than that of cone-ended pile. Since the friction force between pile and soil is not considered, SSPM theoretical solution has some limitations in predicting soil deformation near the pile. For the problem of shallow penetration, the movement of soil particles is mainly inclined upward. The effect of nose cone is the main reason of the different mechanism between flat-ended pile and cone-ended pile.