用抗剪强度指标计算预制桩软黏土侧摩阻力的参数统计分析

参照现有的静力法计算桩侧摩阻力的公式，提出了根据固结快剪c、j指标计算桩侧摩阻力的计算公式，其中有多个参数待定。根据收集到的上海地区19个工程摩擦型预制桩的试桩成果，采用最小二乘法，确定了上海地区主要软土层的待定参数，由统计得到的桩侧摩阻力的计算公式，计算出各试桩在各主要软土层的桩侧摩阻力和各试桩的极限承载力。结果表明，同一土层的各试桩桩侧摩阻力相关性较好，基本符合正态分布规律；单桩承载力计算值与实测值之间的误差较小；用上海地区主要软土层固结快剪c、j指标的上下限可以计算得到桩侧摩阻力上下限，根据19个工程统计得到的平均桩侧摩阻力在上下限之间；桩侧摩阻力的深度效应不明显，桩端持力层条件对桩侧摩阻力发挥有影响。

Statistical analysis of unit frictional force of precast piles in soft clay calculated by shear strength parameters

Based on known equations for predicting skin friction force, a new equation is presented with consolidated-quick shear strength parameters, in which three coefficients will be determined. According to the results of tested frictional piles in 19 projects in Shanghai and the least squares method , coefficients in new equation for different soft clayey strata is determined. Ultimate unit frictional force in different strata is calculated for different tested piles. Results indicate that unit frictional forces in same stratum for different tested piles are distributed in narrow range. Ultimate unit frictional forces obtained by statistical method are located between up and below limitation of which are calculated with up and below values of consolidated-quick shear strength parameters for different soft clayey strata. The effect of depth on unit frictional forces appears undistinguished，but the effect of stratum of pile tip is obvious.