非均匀地基变桩长沉降控制三维有限元协同分析

Three dimensional finite element cooperative analysis of settlement control of variable pile length in non-uniform foundation

为了研究非均匀地基不同区域桩长变化对桩筏基础沉降特性的影响,以某变电站桩筏基础工程为背景,采用PLAXIS 3D软件建立上部荷载-桩筏基础-非均匀地基三维有限元模型,分析了4种非等桩长设计方案下的筏板与地基沉降变形特性。结果表明:筏板沉降分布形态、最大沉降量及其出现的位置均随筏板下不同区域桩长的变化而变化。方案1和方案2的桩长随持力层顶面埋深变化而变化,桩端进入较硬的持力层,但筏板下不同区域的桩长差异较大,筏板沉降非对称分布,最大差异沉降13.70~15.13mm;方案4为等桩长,但由于土层分布不均匀,不同区域的桩侧阻力和桩端阻力发挥各异,筏板沉降亦为非对称分布,最大差异沉降仍达12.57mm;方案3各区桩长变化较小,筏板沉降分布相对较为均匀,其最大沉降量和差异沉降相比方案1分别降低22.8%和37.5%,说明此时桩长与土层分布相协调,沉降控制效果较好。

In order to study the influence of pile length changes in different areas of non-uniform foundation on the settlement characteristics of pile-raft foundation,taking the pile-raft foundation project of a substation as the background,the PLAXIS 3 D software was used to establish a three-dimensional finite element model of upper load-pile-raft foundation-non-uniform foundation,and the settlement and deformation characteristics of the raft and foundation under four unequal pile length design schemes were analyzed.The results show that the distribution form of the raft settlement,the maximum settlement value and its occurrence position all change with the change of the pile length in different areas under the raft.The pile lengths of scheme 1 and scheme 2 change with the buried depth of the top surface of the bearing layer,and the pile ends enter the harder bearing layer.But the pile lengths in different areas under the raft are quite different,and the raft settlement is distributed asymmetrically.The maximum differential settlement is 13.70~15.13 mm.Scheme 4 is equal to the length of the pile,but due to the uneven distribution of soil layers,and the pile side resistance and pile end resistance in different areas play different roles,and the raft settlement is also asymmetrically distributed,and the maximum differential settlement is still up to 12.57 mm.The change of pile length in each area of scheme 3 is small,and the distribution of raft settlement is relatively uniform.Compared with scheme 1,the maximum settlement and differential settlement of scheme 3 are reduced by 22.8%and 37.5%respectively,which shows that the pile length is suitable for the distribution of soil layer,and the settlement control effect is fairly good.