基于三维离散-连续耦合方法的分层介质中桩端刺入数值模拟  

COUPLED 3D DISCRETE-CONTINUUM NUMERICAL SIMULATION OF PILE TIP PENETRATION IN LAYERED MEDIA

作　　者：周健[1] 黄金[1] 张姣[2] 郭建军[3] 王连欣[1] 

机构地区：[1]同济大学地下建筑与工程系,上海200092 [2]上海城市管理职业技术学院土木工程与交通学院,上海200432 [3]四川省川建勘察设计院,四川成都610017

出　　处：《岩石力学与工程学报》2012年第12期2564-2571,共8页Chinese Journal of Rock Mechanics and Engineering

基　　金：高校博士点专项科研基金资助项目(200802470007)

摘　　要：使用离散-连续耦合的方法模拟分层介质中桩端的刺入过程,即在桩端刺入影响较大的区域采用离散元模拟,在离桩较远的区域采用连续单元模拟,开发FLAC3D和PFC3D的结合模块,通过交界处离散颗粒与连续单元的相互接触位移作用实现耦合。通过与有关的数值模拟和离心机试验比较可知,离散-连续耦合方法能高效且合理地模拟分层介质中桩端的刺入过程。研究表明分层介质中桩端刺入存在桩端阻力极限值,上覆软弱层对极限桩端阻的大小的影响效果不明显,但上覆软弱层的存在使得分层介质中桩端阻力达到极限值所需刺入深度远小于纯砂中。综合分析桩端土体宏细观参数的变化规律可得:(1)与桩端接触的土体被逐渐压密,与桩端连成整体,颗粒基本不旋转,以竖向位移为主;(2)与桩侧接触的土体颗粒,沿刺入方向发生滑动,颗粒基本不旋转,以竖向位移为主;(3)稍远区域的颗粒受剪胀作用影响剧烈旋转,以斜向下挤扩运动为主。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.

关 键 词：桩基础 离散-连续耦合 细观力学 分层介质 桩端刺入 

分 类 号：TU47[建筑科学—结构工程]