中文摘要：

为了给群桩基础优化设计以及既有桩基利用条件下的新桩桩长设计提供参考,基于剪切位移法理论,建立单桩桩顶荷载-位移模型;提出等沉降原理,考虑群桩效应建立群桩沉降计算模型,并解析群桩临界桩长关系。根据模型函数优化法验证其桩长关系的合理性,并分析不同土的泊松比、桩间距和桩的弹性模量对群桩长度的影响。结果表明：随长桩长度增加,短桩长度达到峰值后减小;土的泊松比、桩间距和桩的弹性模量等参数取值增大时,短桩长度峰值增大,但增幅不同;在总桩长一定时,与等桩长时相比,变桩长群桩基桩的柔度值相对误差显著减少。

英文摘要：

To provide a reference for the basic optimization design of pile groups and the existing pile foundation reuse with the design of pile length for new pile,based on shear displacement method,a model of load and displacement on single pile head was established.A similar settlement principle of pile-group was proposed for the analysis of the relationship of the criticalpile length of pile group,and the calculation model for settlement of pile group by considering pile group effect was established.The validity of its pile-length relationship was verified by pattern function optimization method and the influences of different soil Poisson＇s ratios,pile spacing and pile elastic modulus on critical length of a pile group were analyzed.The results show that with the increase of long pile length,the length of short pile increases to a peak value and then decreases;as parameter values of soil Poisson＇s ratio,pile spacing and pile elastic moduli increase,the peak value of short pile length increases with different growth amounts.The cases show a significant decrease in relative error of slenderness between foundation piles in an unequallength pile group compared to an equal-length pile group with the same total pile length.