The mechanism of the plugging phenomenon at the tip of vertically loaded open-ended piles was elucidated in this study by using a micro-focus X-ray CT scanner. A series of model tests were conducted on a static penetration test. The model piles used in this study were an open-ended pile and a close-ended pile. The behavior of the surrounding ground at the pile tip is discussed based on observation of the movement of iron particles extracted from visualized X-ray CT data. In addition,the movement of sand particles was extracted using PIV method. The CT images of the experimental results showed that the condition of wedge formation below the open-
ended pile was clearly different from that below the close-ended pile. Although the penetration resistance of the open-ended pile and close-ended pile was similar, the movement of soil inside the open-ended pile was not stopped but restricted, as shown by intermittent increases and decreases in penetration resistance during pile
penetrating. Finally, a plugging mechanism was discussed by analyzing the distribution of the alteration of soil volume and shear strain in X-ray CT images.