(1. Department of Geotechnical Engineering，Tongji University，Shanghai 200092，China；2. School of Civil Engineering and Transportation，Shanghai Technical College of Urban Management，Shanghai 200432，China；3. Sichuan Provincial Chuanjian Investigation and Design Institute，Chengdu，Sichuan 610017，China)
Abstract：A coupled discrete-continuum simulation incorporating three-dimensional aspect is performed to analyze pile penetration process in layered media. A particle numerical simulation program is used to consider the sand near pile as interacted particles by discrete element method(DEM). The sand away from pile are simulated as continua. Binding module of FLAC3D and PFC3D is developed；and the contact between the finite elements and the particles at boundary edges follows the principles defined in the DEM. In comparison with other numerical simulations and centrifuge tests，it is shown that the coupled discrete-continuum simulation can give a proper macro-microscopic description of pile penetration process. There exists ultimate pile tip resistance in the process. Overlying weak layer has a light influence on ultimate pile tip resistance. The penetration displacement in layered media is much shorter than that in pure sand when the pile tip resistance reaches ultimate value. After analyzing the variation of macro-microscopic parameters of soil at pile tip in detail，some conclusions are drawn as follows：(1) The sand particles under pile tip is gradually compacted with vertical movement instead of rotation. (2) The sand particles contacting with the pile skin vertically move with penetration instead of rotation. (3) The sand particles strongly rotate influenced by dilatation and vertically move，which causes the trend of ramming downward.
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2012, Vol. 31 
