论文部分内容阅读
由于受土塞效应等因素影响,开口管桩和闭口管桩在贯入过程中的挤土效应存在明显的差异;然而针对该两者贯入特性的研究相对较少。基于透明土和PIV(Particle Image Velocimetry)技术,开发了相应的桩基贯入模型试验系统,用于桩基贯入过程中桩周土体变形的非插入式测量。试验选用的透明土由玻璃砂和具有相同折射率的孔隙液体制成。该试验系统主要包括:线性激光光源、CCD(Charge-Coupled Device)相机、自动沉桩加载仪和计算机控制系统等。激光射入透明土,和透明土之间的相互作用产生了独特的散斑场,通过CCD相机摄取贯入过程中各个时刻散斑场变形的图片,然后通过PIV技术对这些变形前后的图片进行处理,即可得到整个土体位移场。分别进行了开口管桩和闭口管桩的桩基贯入试验,得到了对应的土体位移场,并对桩基贯入引起的桩周土体径向位移试验结果与圆孔扩张法、应变路径法等理论计算结果进行对比分析;研究结果表明,对于闭口管桩,由于竖向位移的影响,试验值比圆孔扩张法结果小,其与应变路径法更为接近;对于开口管桩,由于沉桩过程中土塞作用,试验值比圆孔扩张法大,其影响不可忽略。
Due to the effect of soil plugging and other factors, the squeezing effect of open pipe piles and closed pipe piles is obviously different during the penetration process; however, there are relatively few studies on the penetration characteristics of the two pipes. Based on the transparent soil and PIV (Particle Image Velocimetry) technology, a corresponding test system for pile penetration model was developed for non-intrusive measurement of soil deformation around pile during pile penetration. The clear earth chosen for the test was made of glass sand and a pore fluid of the same refractive index. The test system mainly includes: linear laser light source, CCD (Charge-Coupled Device) camera, automatic pile loading device and computer control system. The interaction of the laser light into the transparent earth and the transparent earth produces a unique speckle field. The CCD camera captures the images of the speckle field deformation at various times during the penetration process. Then, the images before and after these deformations are processed by the PIV technology Processing, you can get the entire soil displacement field. The pile foundation penetration test of open pipe pile and closed pipe pipe pile were carried out respectively, and the corresponding displacement field of soil was obtained. The results of radial displacement test of soil around pile shaft caused by penetration of pile foundation were compared with that of circular hole expansion method, The results show that for the closed pipe pile, the test value is smaller than that of the circular hole expansion method due to the influence of the vertical displacement, which is closer to the strain path method. For the open pipe pile, Due to the role of soil plug during pile driving, the experimental value is larger than the hole expansion method, and its influence can not be neglected.