软土地区单桩沉降的简化计算方法

根据300根有桩顶和桩端沉降的单桩荷载试验结果,研究了软土地区的单桩变形特性.将单桩分成预制混凝土方桩、空心混凝土桩、钢管桩和灌注桩四大类,利用弹性理论解对实测资料进行分析,得到基于桩长径比的桩身压缩量简化计算方法.结果表明,预制桩的桩身压缩量最大,空心混凝土和钢管桩其次,灌注桩最小,说明挤土效应对单桩的压缩变形有较大影响.用分层总和法分析桩端沉降,在此基础上改进了预估工作荷载下单桩沉降的简化计算方法.300多根试桩的分析结果表明,本方法能较好地预估单桩在工作荷载下的沉降.

A Simplified Calculation for the Settlement of Single Piles in Soft Foundation

The deformation of single piles in soft foundation was studied based on more than 300 in situ data of pile including the settlements at pile-top and piletip. The piles are divided into four types: precast concrete pile,hollow concrete pile,steel pipe pile,and cast-in-place pile.Analyzing the in situ data with elasticity theory,a simplified method to predict the shaft compression of pile was presented based on the pile length-diameter ratio.It is shown that the shaft compression of precast concrete pile is the largest,while the compression of cast-in-place pile is the smallest.Therefore,the deformation of single piles is influenced by the squeezing effect obviously.The settlement at pile bottom was calculated by the layer-wise summation method,and the modified method to compute the settlement of single piles was obtained.The comparison analysis for 300 individual piles shows that the modified method can be used to calculate the settlement of pile at working load very well.