Numerical analysis of negative skin friction in pile foundations

• Main Authors: Yu-an Shih, 施昱安
• Other Authors: Jin-hung Hwang
• Format: Others
• Language: zh-TW
• Published: 2009
• Online Access: http://ndltd.ncl.edu.tw/handle/43836670404546274919

碩士 === 國立中央大學 === 土木工程研究所 === 98 === This research uses finite difference program FLAC2D to observe negative skin friction behavior of a single pile. The numerical soil model consists of two layer soils, the upper compressible soft clay and the lower gravel bearing layer. The aim of this research is to find the differences of negative friction behavior between friction and end-bearing piles, and to clarify the influences of different loading patterns and bearing conditions. The result shows that the downdrag force of a pile and neutral point location depend on the relative displacement in the interface of pile and soil. Increasing loading magnitude and area will cause more dragload and settlement, while the neutral point moves down in the meantime. Compared with friction pile, end-bearing pile has more dragload and smaller settlement, it is necessary to check the buckling potential of pile material. By varying the stiffness ratio between compressible and bearing layers, the larger the stiffness of bearing layer, the less the pile settlement and the more the pile dragload within 10 times stiffness ratio, but there is no obvious variation when the stiffness ratio is greater than 10. Moreover, applying axial loading then surcharge will have larger dragload than the reverse loading sequence but with similar pile settlement. Therefore, changing loading sequence might be chosen to be one of the ways to reduce dragload.