楔形角对基桩负摩阻力特性影响的数值模拟分析

负摩阻力引起的基桩下拽力和下拽位移是桩基础设计中必须考虑的重要问题之一,楔形桩中的倒楔形角是一种有效减少基桩下拽力和下拽位移的结构形式;但是针对楔形角在减少负摩阻力效果方面的研究却相对较少。结合工程实例,建立单、群桩负摩阻力特性分析的三维数值模型,并通过与现场试验结果和已有文献分析结果的对比分析,验证所建模型的准确性和可靠性。对比分析4种不同楔形角组合形式对基桩负摩阻力的减少效率以及是否考虑土体固结形式对基桩负摩阻力特性的影响规律。研究结果表明,桩体上部分楔形角对基桩负摩阻力特性影响较显著;桩体下部分楔形角的影响相对不明显;小角度范围内,楔形角增加1度,最大基桩下拽力减少约20%。

Numerical Analysis on Negative Frictional Resistance of Pile Influenced by Taper Angles

Tapered pile, which has greater top cross than bottom ones, is one of the effective methods to reduce dragload and downdrag on pile foundations under negative frictional resistance. Three-dimensional elasto-plastic numerical analyses on dragload and downdrag of pile group were carried out. The correctness of numerical model was verified by comparing with previous studies and case studies. Four different taper angles (φ) were taken into account for the reduction ratio of negative frictional resistance. Taper angle equal to 0° (vertical pile) were also taken into analysis for comparison. The results show that the negative frictional resistance of pile was influenced by the taper angle of the upper part of pile effectively, while it was influenced little by the lower part of pile. The maximum dragload of pile was reduced nearly 20% with 1 degree taper angle increasing under the small taper angle condition.