粘土中不同桩端条件下桩承载性状的模型试验

对桩身位于淤泥质粘土中而桩端支撑于强持力层(砂土)和弱持力层(粉质粘土)两种情况下桩的承载性状差异进行了室内模型试验研究,结果表明:淤泥质粘土存在应变软化特征;桩端持力层强度越大,桩侧摩阻力增加越大.实验结果解释了上海市<地基基础设计规范>关于桩身大部分位于淤泥质粘土中且桩端支撑于第⑤层土(弱持力层)的预制桩,桩侧摩阻力作"适当折减"的原因.

Model Test on Pile Bearing Behaviors in Clay Under Different Pile Tip Conditions

A laboratory model test was conducted to reveal the difference of bearing capacity of a pile that stays in the mucky clay and the tip of which enters strong bearing layer (sand) and weak bearing layer (silt clay)respectively.The results show that the mucky clay has the characteristic of strain softening; the stronger the strength of bearing layer becomes, the more the pile skin friction increases. The results can explain why the skin friction of the precast pile in mucky clay should be discounted properly in the case that the pile tip bearing stratum is the 5th layer (weak bearing layer)as stipulated in Shanghai Foundation Design Code.