灌注桩桩—土界面粗糙度及强度理论研究

Roughness and soil-pile interface strength of cast-in-place piles

文章开发了可模拟实际灌注桩成型过程的混凝土浆液-土固化成型装置,开展不同灌注桩深度处混凝土浆液-土固化成型试验,探究浆液自重应力对灌注桩表面粗糙度的影响规律,进而提出考虑粗糙度特征的桩—土界面强度理论。结果表明:随着混凝土浆液自重应力增加,混凝土浆液对桩周土体的挤压、劈裂作用更为显著,使得桩—土界面粗糙度随深度增加而近似线性增长的规律;而后引入界面剪切系数i来表征桩—土界面粗糙度对界面间发生桩—土相对滑移破坏或土自身剪切破坏的影响,与已有试验结果对比表明,考虑粗糙度的强度理论可以较好地预测不同粗糙度下桩—土界面极限强度;最后探讨了理想粗糙面情况下界面剪切系数i与剖面长度比、凹槽形状的数学关系。

This paper investigate the roughness and pile-soil interface strength of cast-in-place piles.An apparatus was developed to simulate the construction process of a cast-in-place pile.A series of tests were conducted to study the effect of the dead weight of the concrete slurry on the roughness of the soil-pile interface.A model was proposed to estimate the strength of the interface.An interface shear ratio i is introduced to describe the effect of the roughness on two failure modes of the interface,i.e.pile-soil slipping or soil shearing.The results show that increasing the dead weight of the concrete slurry results in significant squeezing and splitting of the slurry into the soil,and thus leading to rougher pilesoil interface.The roughness increases nearly linearly with the pile length.The proposed model was used to predict the ultimate strength of pile-soil interface with different roughness.Effects of section length ratio and interface characteristics under an ideal roughness are discussed.