考虑加载过程及桩体固结变形的碎石桩复合地基固结解析解

ANALYTICAL SOLUTION FOR CONSOLIDATION OF STONE COLUMNREINFORCED FOUNDATIONS TAKING INTO ACCOUNT CONSOLIDATION DEFORMATION OF PILE UNDER PROGRESSIVE LOADING

为了完善碎石桩复合地基固结理论,通过假设从桩体排出的水量等于流入桩体的水量与桩体体积变化之和以及地基扰动区土体水平渗透系数呈线性变化,并考虑上部荷载逐渐施加,推导了考虑桩体体积变化的碎石桩复合地基超静孔压及固结度解析解。当加载时间趋于零时,本文解可退化为瞬时加载情况下的解;当加载时间及桩径同时趋于零时,本文解可进一步退化为Terzaghi一维固结解,这证明了本文解的正确性。通过与已有解的比较,对地基固结性状进行了分析。结果表明,加载过程对地基固结度影响显著,加载历时越长,固结越慢;在各种条件下,不考虑桩体固结变形时地基固结始终比考虑桩体变形时快,并且其影响随着加载历时变小、桩径比变小、桩土模量比变小、桩土渗透系数变小而逐渐增大,这说明在实际工程固结计算中不考虑桩体固结变形是偏于不安全的。

For the sake of improvement of the composite foundations consolidation theory,an analytical solution is obtained for consolidation of stone column-reinforced foundations taking into account the consolidation deformation of pile under progressive loading. Column consolidation and deformation are considered with the following two assumptions:( 1) the quantity of water flowing through the disturbed soil zone into the column is not equal to that flowing out from the column and( 2) the difference between them is equal to the volume change of the column. In addition,the linear distribution pattern of the horizontal permeability of soil in the disturbed zone is also taken into account for the disturbance effect of columns construction on the surrounding soil. To prove the correctness of thesolution,a discussion is performed in the article. If the loading time tends to zero,the obtained solution can be convert to the solution in the condition of constant load. Furthermore,if the loading time and the size of stone columns tend to zero at the same time,the obtained solution can be convert to the one-dimensional solution obtained by Terzaghi. In the end,the average degree of consolidation of a composite foundation is obtained and discussed.The results show that the influence of loading process on the consolidation is obvious. The consolidation rate under the linear distribution pattern of the horizontal permeability of soil in the disturbed zone is faster than the consolidation rate in the condition of constant permeability. The consolidation rate considering deformation of pile is slower than consolidation rate using traditional assumptions. So that it is unsafe to ignore deformation of pile.Furthermore,the differences increase gradually as the loading time,the radius ratio,the stress ratios and the permeability coefficient ratios decrease.