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桩侧表面粗糙程度是决定桩土接触面力学特性的主要因素之一,其对桩侧摩阻力的发挥具有重要影响。为研究桩侧表面粗糙度对桩土接触面剪切特性的影响,制作不同粗糙度的混凝土板模拟桩侧表面,并给出了混凝土表面粗糙程度计算方法。采用大型室内剪切系统,依次在不同法向应力下进行剪切试验,从剪应力-剪切位移关系、剪胀性和接触面抗剪强度三方面对接触面力学特性进行分析。结果表明:接触面剪应力-剪切位移曲线大体呈折线型,存在较为明显的应变软化现象。表面粗糙度越大,剪应力峰值越高,不同粗糙度界面达到剪应力峰值强度所对应的剪切位移变化不大。在法向应力较低时接触面有剪胀现象发生,随着粗糙度的增大,剪胀现象越明显;法向应力较高时则出现剪缩。接触面抗剪强度及残余剪切强度均随着表面粗糙度的增大而增大。根据试验结果建立的接触面力学参数与混凝土表面粗糙度关系式,可为进一步研究预制抗拔桩承载力发挥机理提供参考。
Pile surface roughness is one of the main factors that determine the mechanical properties of pile-soil interface, which has an important influence on the pile-side frictional resistance. In order to study the effect of pile surface roughness on the shear characteristics of pile-soil interface, the concrete slab with different roughness is simulated to simulate the side surface of pile, and the method to calculate the surface roughness of concrete is given. A large indoor shear system was used to conduct shear tests under different normal stresses. The mechanical properties of the contact surfaces were analyzed from three aspects: shear stress-shear displacement, dilatancy and shear strength. The results show that the shear stress-shear displacement curve of the contact surface is roughly in the form of a polygonal line, with obvious strain softening phenomenon. The larger the surface roughness is, the higher the peak value of shear stress is. The shear displacement corresponding to the peak shear strength at different roughness interfaces does not change much. When the normal stress is low, the dilatancy occurs on the contact surface, and the dilatancy becomes more obvious with the increase of the roughness. When the normal stress is high, shearing shrinkage occurs. The contact surface shear strength and residual shear strength increase with the increase of surface roughness. According to the experimental results established contact surface mechanical parameters and the relationship between the surface roughness of concrete can provide reference for further study on the mechanism of bearing capacity of precast uplift piles.