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在典型的上硬、下软红黏土地层中静压管桩滞留的残余应力对基桩承载特性有较大影响。通过自行设计模型试验设备进行红黏土地层单、群桩静压闭口管桩室内试验,分析3种桩径下静压单、群桩残余应力的变化规律及时间效应。结果表明,静压管桩桩身残余应力沿桩身从上到下先增大后变小,呈折线型分布;对于典型的红黏土上硬、下软地层,桩端持力层位于硬塑层和可塑层时,桩身和桩端残余应力均较小;当管桩压入到基岩持力层后桩端受约束增强,桩身和桩端残余应力明显增大;静压单桩完成后静置初期桩身残余应力时间效应比较明显,减小幅度较大,复压后而后随着休止时间的延长,桩身残余应力呈指数型衰减至一较低稳定值;静载试验时忽略残余应力就将认为整个桩身所受压力偏小,偏大计算中性面以上侧摩阻力7.97%,偏小计算中性面以下侧摩阻力8.33%和桩端阻力2.29%。
In a typical upper and lower soft red clay stratum residual pressure pile static pressure pile bearing characteristics have a greater impact. By means of designing the model test equipment by ourselves, the single-group and group-group static pressure closed-mouth pipe piles in the red clay stratum were tested in laboratory. The variation rules and time effects of the residual stress of the single-group and group pile under static pressure were analyzed. The results show that the residual stress of the static pressure pipe pile body first increases and then decreases from the top to the bottom of the pile, and presents a polygonal line distribution. For the hard and soft sub-layers on the typical red clay, When the piles are pushed into the bedrock bearing layer, the pile ends are restrained and strengthened, the residual stress of the piles and pile ends obviously increases. After the completion of initial static pile residual stress time effect is obvious, a larger reduction, after re-compression and then with the rest time extension, the pile residual stress exponentially decay to a lower stable value; static load test Neglecting the residual stress, the pressure on the entire pile will be considered as being small, with a 7.97% above the neutral side and a 8.33% below the neutral side and 2.29% at the pile end.