Friction and energy dissipation along the interface between sand and construction materials

本研究关注的是地基与结构基础之间的接触面特性。对砂土与建筑材料之间的摩擦力进行了室内试验。在此基础上，分析了影响摩擦阻力的因素。本研究亦尝试将界面滑移解释为一能量耗散过程。研究结果表明：钢-砂屈服摩擦系数随钢表面粗糙度、砂中径和砂种类的不同而变化。建议的标准化粗糙度是以Rmax表示的钢粗糙度与砂的中值直径的比率。摩擦系数与标准化粗糙度之间具有很高的相关性，由于砂组构的扰动，沿粗糙界面形成沿着剪切带。在单调加载条件下，沿光滑界面没有形成沿着剪切带。当界面反复滑动时，甚至沿着光滑界面形成剪切带;当界面粗糙时，摩擦阻力随循环加载次数的增加而减小。这是由于沿界面沿着形成了剪切带。在光滑界面条件下，当颗粒沿界面沿着破碎明显时，摩擦阻力随加载次数的增加而增大。反复荷载作用下，砂-混凝土摩擦阻力收敛于砂的最大剪应力比，砂-混凝土摩擦系数随混凝土粗糙度和粒径中值的变化而变化。粗糙度与摩擦系数相关性较好，摩擦系数与粗糙度的相关性较好，界面屈服时，界面沿着方向的塑性功大于砂体。能量沿界面沿着方向的耗散主要是由于界面滑移、剪切带的形成和剪切带的变形。

This study concerns the behavior of interfaces between ground and structural foundation. Laboratory tests were carried out on the friction between sand and construction materials. Based on the results, analyzed were the factors influential to the frictional resistance. This study also includes an attempt to interpret the interface sliding as an energy dissipation process. Followings are conclusions of this study.Sand-steel coefficient of friction at yield varies with surface roughness of steel, median diameter and type of sand. Normalized roughness proposed is the ratio of the steel roughness in Rmax to the median diameter of sand. There are high correlations between coefficient of friction and normalized roughness.A shear zone formed along a rough interface due to the disturbance in sand fabric. There was no formation of a shear zone along a smooth interface under monotonic loading. When the interface slid repeatedly, a shear zone formed even along a smooth interface.When the interface was rough, the frictional resistance decreased with the increase in number of in cyclic loading. This is due to the formation of a shear zone along the interface. In case of smooth interface, the frictional resistance increased with loading number if particle crushing was significant along the interface. The frictional resistance converged to the value of maximum shear stress ratio of sand under repeated loading.Sand-concrete coefficient of friction varies with roughness of concrete and median particle diameter. The roughness evaluated by Rp rather than Rmax showed a high correlation with the coefficient of friction.At the yield of interface, plastic work along the interface become larger than that of sand mass. The energy dissipation along the interface is attributed to the slipping of interface, shear zone formation and the deformation of shear zone.