考虑散体桩变形时复合地基径竖向固结解析解  

Analytical solutions for radial and vertical consolidation of composite foundation considering the deformation of granular columns

作　　者：张绍勇 许波[2] 

机构地区：[1]浙江省地球物理地球化学勘查院,浙江杭州310005 [2]香港华艺设计顾问(深圳)有限公司南京分公司,江苏南京210037

出　　处：《水文地质工程地质》2015年第5期54-61,共8页Hydrogeology & Engineering Geology

摘　　要：现有散体桩复合地基固结问题的解析解大都在传统砂井地基等竖向应变假定条件下建立的,而且,在建立求解初始条件时,不能满足复合地基"应力集中"这一受力特点;另外,现有解答的固结微分方程为近似径竖向固结微分方程。为此,针对散体桩复合地基固结问题,抛弃桩周流量连续假定,采用桩土等竖向应变假设,根据复合地基"应力集中"引入新的初始条件,考虑涂抹以及平均附加应力沿深度任意分布,推导了瞬时加载条件下复合地基径竖向同时固结下的解答,给出了超静孔隙水压力和地基整体平均固结度的显示表达式,分析了平均附加应力分布形式,桩径比、置换率和涂抹参数对固结的影响。计算结果表明,平均附加应力沿深度倒三角衰减分布时复合地基固结最快,梯形衰减分布次之,矩形分布最慢;当桩径比较小时,不考虑桩体径向渗流会低估复合地基的固结速率;地基固结速率随置换率增大而加快,随涂抹参数kh/ksh比值增大而减慢,且两者对固结速率的影响均显著。The existing analytical solutions of granular columns on composite foundation are mostly established based on the traditional equal vertical strain assumption and the initial condition cannot meet the mechanical characteristics of ＂stress concentration＂ on composite foundation. In addition, the existing radial and vertical consolidation differential equation is an approximate one. Therefore, the assumption of flow continuality at the pilesoil interface is discarded and the equal vertical strain assumption is adopted to solve the consolidation problem with granular composite foundation, and a new initial boundary condition is introduced based on ＂stress concentration＂ on composite foundation. The effect of smear is taken into account, together with an arbitrarily distributed mean additional stress increase in the ground. Explicit expressions of excess pore water pressure and total average degree of consolidation are presented under instantaneous loading. The influences of distribution form of mean additional stress, pile diameter ratio, replacement rate and smear parameter kh/ksh are analyzed. The results shows that the consolidation rate is at its maximum value when the mean additional stress distributes in the form of a triangle and is at its minimum value when it distributes in the form of a rectangular, while trapezoidal distribution occurs between them. When the value of the diameter ratio is relatively small, the consolidation rate is underestimated by the solution derived without consideration of the radial seepage in pile. The influence of the replacement ratio and smear parameter kh/kshon the consolidation rate are significant： the larger the replacement ratio, the faster the consolidation is, and the larger the smear parameter kh/ksh, the slower the consolidation rate is.

关 键 词：散体桩 复合地基 固结 瞬时加载 解析解 

分 类 号：TU473.12[建筑科学—结构工程]