水平单向及多向载荷下单桩响应的数值研究

Numerical study on response of a single pile under unidirectional and multidirectional horizontal loadings

利用大型有限元分析软件ABAQUS,建立砂土中单桩的三维弹塑性数值分析模型,通过三轴试验确定土体相关参数,研究水平单向载荷作用下桩头自由和固定时单桩的响应特性,及多向加载路径对单桩承载力的影响.结果表明,桩头自由的单桩在水平力作用下桩身的最大弯矩在土面下约4倍桩径处,桩运动前方土体隆起的最大值出现在桩前约0.5倍桩径处;桩头固定单桩的水平承载力约为桩头自由的2.65倍,且出现较大的桩顶弯矩;多向加载条件下的桩头水平承载力与单向加载条件相比明显减小,随着短长轴比增加,水平加载主方向(X方向)承载力降低,载荷最大值出现得更早.

In many practical projects,pile foundations are required to resist large horizontal loadings besides vertical loadings.A three-dimensional elastoplastic numerical analysis model was set up,useing the FEM software ABAQUS,to study the response of a single pile with a free head or a fixed head under the unidirectional horizontal loading,and to analyze the effect of the multidirectional loading path on the lateral loading capacity of the single pile.In these analyses,the parameters of the soil were determined according to the data of the triaxial tests.It is revealed from the numerical analyses that for the lateral loaded free-head pile,the maximum bending moment occurs at 4D below the soil surface and the maximum vertical displacements of the soil occurs at 0.5D in front of the pile.The lateral loading capacity of the fixed-head pile is about 2.65 times that of the free-head pile,and the maximum bending moment of the former is much larger than that of the latter.The lateral loading capacity under multidirectional paths is apparently smaller than that under unidirectional path.This is consistent with that observed in the experiments.With the increasing aspect ratio,the loading capacity reduces and the maximum force appears earlier.