Experimental study on interface properties between crushable soils and pile materials

通过土与钢材料之间的直剪试验，探讨影响摩擦系数的因素。以被称为软岩的硅藻质泥岩和典型的可破碎土白苏砂作为土样。制备表面粗糙度Rmax分别为10、30、40gm的钢板作为桩材。其他实验参数为法向压力、cm、剪切位移速率为2mm/mm和20mm/mm、重复加载次数。研究结果表明：1)桩土界面处抗剪强度受Mohr-Coulomb准则支配，抗剪强度与有效正应力siguma_n成正比；2)摩擦系数m随重复加载次数的增加而向土体内部摩擦系数方向增大。3)这种现象与土壤颗粒的挤压有关。假定颗粒粉碎产生的较细的土粒在桩表面埋沟，随着土粒粉碎的进行，桩-土滑移模式转变为土-土滑移模式。

Direct shear tests between soils and steel materials were conducted in this research to investigate influential factors on coefficient of friction. Diatomaceous mudstone known as a soft rock, and Shirasu sand that is a typical crushable soil were used as soil specimen. Steel plates having different surface roughness, Rmax, of 10, 30, 40gm, were prepared as pile materials. Other experimental parameters were normal pressure, cm, shear displacement rates of 2mm/mm and 20mm/mm, and number of repeated loading.Principal findings from this research are as follows :1)The shear strength at the pile-soil interface is dominated by Mohr-Coulomb criterion where shear strength is proportional to effective normal stress siguma_n.2)Coefficient of friction m is increased with number of repeated loading toward internal coefficient of friction of soil.3)This phenomenon is associated with crush of soil particles. It is presumed that finer soil particles produced by particle crush bury ditches on the pile surface so that pile-soil slip mode changes to soil-soil slip mode as crush of soil partilces is progressed.