采用三维罚单元对桩基沉降的研究

为了研究桩在荷载作用下的几何特性、物理特性和层状土及其物理特性对桩基沉降的影响,选用模拟承台与桩土连接条件的罚单元,考虑承台与桩土的特性,运用虚位移原理推导了承台与桩-土的罚单元刚度矩阵,利用编制的三维有限元程序,分析得出在竖向荷载作用下,承台与桩体、土体之间存在着变形协调条件,用三维罚单元可以模拟承台与桩土之间连接问题的情况;增加桩体弹模,可有效减少桩基的沉降;与桩长相比,桩径的变化对桩基的沉降影响更大,对于控制沉降更为有效;在考虑土的层状特性的基础上,土的压缩模量变化对桩基沉降有一定的影响,可降低桩与土体滑移破坏的突然性;与土的内聚力相比,内摩擦角对沉降有更大的影响.

On the pile settlement by applying 3D penalty element

In order to study how the pile geometry,mechanical characteristic of pile,soil mechanical characteristic and interface characteristic have influence on the pile settlement,the element stiffness matrix of penalty element that can simulate process between piles(soil) and platform under vertical load is obtained by applying theory of virtual displacement with considering characteristic of soil.The coordination condition has been analyzed between piles to platform and soil under the vertical load by 3D-FEM.The penalty element is used to solve harmony of displacement on soil and pile.Subsequently,several appropriate and usefulness conclusions have been obtained.The change of pile radius can reduce the pile settlement more effectively;and compare with the increment elastic module of pile,it can effectively reduce the pile settlement.Considering the layer mechanical characteristic of soil,the change of the elastic module of soil can influence on the pile settlement and reduce the slide accidentally between the pile and soil.The friction angle has more influence on the pile settlement than the cohesion of soil.