Evaluation of three dimensional vertical and lateral bearing capacities of pile foundations using X-ray CT

本研究的目的是利用x射线CT扫描仪评估桩基的竖向和横向承载力。这两个主题的内容分别总结如下：(1)竖向承载力有几种类型的破坏模式，如Terzaghi， Meyerhof和Vesic提出的破坏模式。但这些都是为了设计计算而提出的，并不是基于对实际行为的密切观察。本研究的目的是利用x射线CT扫描仪可视化和表征垂直荷载桩基下地基的破坏模式。进行了桩端形状、加载过程影响、土密度、加载速度等不同条件下的一系列模型加载试验，并对模型地基进行了扫描。最后，在不破坏的情况下，首次实现了竖向荷载作用下桩基承载力的三维可视化评价，进一步证明了x线CT是岩土工程研究的有力工具之一。(2)横向承载能力本研究的目的是利用x射线CT研究横向荷载桩在砂土中的三维破坏模式。本文研制了一种新型的模型加载试验装置，并利用该装置进行了一系列的模型加载试验。然后，对模型地基在桩头处施加不同水平荷载时进行CT扫描。不仅重建了地面断面图像，还重建了三维图像。为了获得有效的CT图像，我们进行了适当的图像处理分析。在不破坏的情况下，将横向荷载作用下地基的破坏形态三维可视化。还进行了定量讨论。最后，利用x射线CT技术首次实现了桩侧荷载作用下地基三维破坏形态的可视化。少

The objective of this research is to evaluate both vertical and lateral bearing capacities of pile foundations using X-ray CT scanner. The contents of these two topics are summarized separately as follows :(1)Vertical bearing capacityThere are several types of failure patterns such as those proposed by Terzaghi, Meyerhof and Vesic. But those have been proposed for the purpose of design calculation and are not based on close observation of real behavior. The objective of this research is to visualize and to characterize the failure patterns of the ground under vertically loaded pile foundation using X-ray CT scanner. Here, a series of model loading tests with different conditions such as shape of pile tip, effect of loading process, soil density and loading speed were conducted and the model ground was scanned in each case. Finally, the bearing capacity mechanism due to vertically loaded pile was visualized and evaluated in three dimensions without any destruction for the first time and … More it is convinced that X-ray CT is one of powerful tool in geotechnical engineering.(2)Lateral bearing capacityThe objective of this research is to investigate three dimensional(3-D) failure patterns in sand due to laterally loaded pile using X-ray CT. Here, a new apparatus of model loading test especially for X-ray CT was developed and a series of model loading tests were conducted using this apparatus. Then, CT scanning was done for the model ground at several levels of loadings which were applied at the pile head. Not only cross sectional images for the ground but also those in 3-D were reconstructed. Here, a proper image processing analysis was conducted in order to obtain effective CT images. And, the failure patterns of the ground under laterally loaded pile were visualized without any destruction in three dimensions. Quantitative discussion was also examined. Finally, it is convinced that three dimensional failure patterns of the ground due to laterally loaded pile were visualized for the first time using X-ray CT. Less