散体颗粒材料被广泛应用于基础设施工程建设中。为了深入研究动态法向应力振幅对散体材料剪切滑移特性的影响,本文以标准干砂为研究对象,采用大型动态直剪试验机对标准砂进行变法向应力剪切试验。结果表明:(1)剪切应力、摩擦系数以及法向位移均伴随着法向力的改变呈周期性变化;(2) 随动态法向应力振幅的增大,稳定滑移阶段剪切应力的峰值和谷值均先增大后减小,最大峰值剪切应力大于静态法向应力下峰值剪切应力;(3)剪切应力峰值与法向应力峰值间存在一个明显的相位差,该相位差随着剪切变形的增大而减小,随着动态法向应力振幅的增大而增大,然而剪切应力谷值与法向应力谷值间却不存在相位差;(4)动态法向应力下的法向位移随振幅的增大而增大,且远大于恒定法向应力下的法向位移。研究可为实际工程中动力荷载条件下下砂土强度参数的确定提供参考。
As a typical granular material, sand is widely used in infrastructure construction. In order to study the influence of dynamic normal stress amplitude on the frictional characteristic of granular material, a large dynamic shear box device is used to perform the dynamic shear test on standard sand. Experimental results show that: (1) The changing pattern of shear stress, friction coefficient and normal displacement under dynamic normal stresses show variation characteristics. (2) In the stable sliding stage, the peak and valley values of shear stress increase first and then decrease with increasing normal stress amplitude, and the maximum peak shear stress is larger than that under constant normal stress. (3) There is an obvious phase shift between the peak normal stress and peak shear stress, which decreases with increasing shear displacement and increases with increasing dynamic normal stress amplitude. However, there is no phase shift between the valley normal stress and shear stress. (4) The normal displacement under dynamic normal stress increases with increasing dynamic normal stress amplitude, and it is much larger than that under constant normal stress. The study can provide a reference for determining the strength parameters of sand under dynamic load conditions in practical engineering.
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