Abstract Sand–concrete interface direct shear tests were used to investigate the effects of surface roughness, surface waviness, mean sand diameter and relative density on interface strength and behavior under different confinement conditions. Extreme concrete surface textures, including smooth, rough and rough–wavy textures, were reproduced. Surface plowing was assessed via image analysis, laser scanning and extended multifocal micrographs. The experimental results showed that smooth concrete surfaces exhibited high values of interfacial–to–internal friction angle ratios, ranging 88–90%, due to the angular shape of sand particles. The rough concrete surfaces generated higher interface strength than smooth concrete surfaces; however, the interface strength was still inferior to the surrounding sand strength. Surface plowing, which identified a mixed shear plane at the sand–concrete interface, was developed as particles were detached from the surface, thus inhibiting the interface friction angle from reaching the sand friction angle. Higher sand–concrete interface strength was achieved as surface waviness increased, and interface friction angles greater than the surrounding sand friction angle were reached. Under a constant normal stiffness condition, significantly high interface strength is achieved due to the increase of the current normal stress, which was directly influenced by the initial normal stress, stiffness, surface roughness, mean sand diameter and relative density; surface waviness did not have a marked effect on the normal stress variation. Based on these results, multiple regressions were proposed to estimate the sand–concrete interface strength by the interfacial–to–internal friction angle ratio and the effect of the constant normal stiffness condition.

中文翻译：

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砂-混凝土界面响应：表面纹理和约束条件的作用

摘要 通过砂-混凝土界面直剪试验研究了不同约束条件下表面粗糙度、表面波纹度、平均砂直径和相对密度对界面强度和行为的影响。再现了极端的混凝土表面纹理，包括光滑、粗糙和粗糙的波浪纹理。通过图像分析、激光扫描和扩展的多焦点显微照片评估表面耕作。实验结果表明，由于砂粒的角形状，光滑的混凝土表面表现出很高的界面内摩擦角比值，范围为 88-90%。粗糙的混凝土表面比光滑的混凝土表面产生更高的界面强度；然而，界面强度仍然不如周围的砂强度。地表耕作，确定砂混凝土界面处的混合剪切面，随着颗粒从表面分离而发展，从而抑制界面摩擦角达到砂摩擦角。随着表面波纹度的增加，实现了更高的砂-混凝土界面强度，并达到了大于周围砂摩擦角的界面摩擦角。在恒定的法向刚度条件下，由于当前法向应力的增加，界面强度显着提高，这直接受初始法向应力、刚度、表面粗糙度、平均砂直径和相对密度的影响；表面波纹度对法向应力变化没有显着影响。基于这些结果，