Loading Sequence Effects on Dragload and Downdrag for Pile Foundation.pdf

Trans. Tianjin Univ. 2010, 16: 203-208 DOI 10.1007/s12209-010-0036-z Accepted date: 2009-03-26. ?Supported by National Natural Science Foundation of China (No and China Postdoctoral Science Foundation (No.20090461062). KONG Gangqiang, born in 1982, male, Dr. Correspondence to KONG Gangqiang, E-mail: gqkong1@163.com. Loading Sequence Effects on Dragload and Downdrag for Pile Foundation* KONG Gangqiang (孔纲强)1, 2, 3，YANG Qing (杨 庆)1，LUAN Maotian (栾茂田)1 (1. State Key Laboratory of Coastal and Offshore Engineering, Dalian University of Technology, Dalian 116024, China; 2. Key Laboratory for Geomechanics and Embankment Engineering of Ministry of Education, Hohai University, Nanjing 210098, China; 3. Geotechnical Research Institute, Hohai University, Nanjing 210098, China) ? Tianjin University and Springer-Verlag Berlin Heidelberg 2010 Abstract：Negative skin friction (NSF) is one of the important problems when designing a pile foundation. How- ever, the influence of loading sequence on the dragload and downdrag for pile foundation is seldom studied. In this paper, a three-dimensional numerical model was established using FLAC3D. Compared with the results of model test, the established model could be used to study the NSF of pile foundation. The influencing factors were discussed in- cluding the length-diameter ratio of pile and the loading sequence of pile head load and surcharge. A case history was analyzed using FLAC3D. The calculated results are in good agreement with the measured results. It is concluded that the dragload and downdrag are remarkably influenced by the loading sequence of pile head load and surcharge. The dragload and downdrag reach the maximum values under the condition of surcharge after pile head load. Keywords：pile foundation; dragload; downdrag; negative skin friction; load sequence; numerical analysis The additional compressive force (dragload) in a pile and the excessive pile settlement (downdrag) c