[论文解读] Effect of Particle Size on the Shear Strength Behavior of Sands

Nazmul Islam, Ayesha Siddika+3 more|arXiv (Cornell University)|Feb 25, 2019

Granular flow and fluidized beds被引用 13

一句话总结

本研究通过在八种粒径（0.075–2.76 毫米）的均粒及级配砂样上进行直剪试验，探究了颗粒尺寸对砂土剪切强度的影响。结果表明，随着颗粒尺寸增大，内摩擦角和最大剪应力均持续升高，级配砂因颗粒嵌锁作用增强及荷载传递效率提高而表现出更高的强度，该结论通过一个将微观尺度颗粒行为与宏观尺度剪切强度响应相关联的理论模型得到验证。

ABSTRACT

During plastic deformation of granular materials due to loading, the stress-strain and strength characteristics of sand grains are influenced with grain size, their distribution and packing. Also the macroscopic behaviour of granular materials changes with the variation of microscopic behaviour. Particle size is one of the important properties which plays a dominant role on the stress, strain and strength responses of granular materials. Alteration of grain size results in the change of void ratio as well as particle effective contact area revolutionized and the load distribution mechanism of particle to particle contact. To evaluate the effect of particle size, a series of direct shear tests were performed considering uniform particles of eight samples (0.075, 0.15, 0.212, 0.300, 0.600, 1.18, 1.72 and 2.76 mm) and graded particles of two samples (0.075-1.18 mm and 0.075-2.36 mm). Three types of normal loads (0.05, 0.10 and 0.15 kN) were selected for each test. For uniform particles, particles retained on individual sieve size were considered and in graded particles combination of each uniform particle pondered. A theoretical approach was also proposed to correlate the particle size and macroscopic response. From the experimental results, it was observed that for each set of normal load with the increase of particle size ,angle of internal friction as well as maximum horizontal shear stress increases for uniform sands and a similar response was noticed in graded sands but the larger the gradation the higher the shear strength. Maximum horizontal shear and angle of internal friction with respect to particle size is also influenced by normal stress. Experimental results have good agreement with the theoretical approach.

研究动机与目标

• 分析颗粒尺寸对颗粒材料（特别是砂土）剪切强度行为的影响。
• 评估粒径变化对颗粒集合体中应力-应变响应、孔隙比及颗粒接触面积的影响。
• 研究颗粒级配在通过改善颗粒嵌锁与荷载传递效率方面对剪切强度的增强作用。
• 建立并验证一个理论模型，将微观尺度颗粒特性与宏观剪切强度响应相联系。

提出的方法

• 对10种砂样进行了系列直剪试验：八种均粒颗粒（0.075–2.76 毫米）和两种级配组合（0.075–1.18 毫米和0.075–2.36 毫米）。
• 对每种样品施加三种法向应力水平（0.05、0.10 和 0.15 kN），以评估应力依赖性行为。
• 收集了每种颗粒尺寸和级配条件下峰值水平剪应力及内摩擦角的实验数据。
• 提出一个理论框架，将颗粒尺寸与宏观剪切强度相关联，基于有效接触面积变化与荷载传递机制的分析。
• 通过将理论模型预测结果与所有颗粒尺寸和法向荷载下的实验结果进行对比，验证了该理论模型。

实验结果

研究问题

• RQ1 在均粒砂中，颗粒尺寸增大如何影响内摩擦角？
• RQ2 颗粒尺寸对颗粒集合体中最大水平剪应力有何影响？
• RQ3 与均粒颗粒尺寸相比，颗粒级配如何改变剪切强度响应？
• RQ4 法向应力在颗粒尺寸与剪切强度关系中起多大调节作用？
• RQ5 理论模型能否有效基于颗粒尺度特征（如尺寸和接触面积）预测宏观剪切强度？

主要发现

• 对于均粒砂，内摩擦角和最大水平剪应力均随颗粒尺寸增大而升高，且在所有法向应力水平下均呈现一致趋势。
• 所测试的最大颗粒尺寸（2.76 毫米）在所有法向荷载下均表现出最高的内摩擦角和峰值剪应力。
• 级配砂（0.075–1.18 毫米和 0.075–2.36 毫米）的剪切强度高于相同最大颗粒尺寸的均粒砂，原因在于颗粒嵌锁作用增强及荷载分布更高效。
• 级配程度与剪切强度呈正相关，表明更宽的颗粒尺寸分布可提高宏观抗剪阻力。
• 理论模型与实验数据高度吻合，证实了颗粒尺寸变化引起的有效接触面积变化及荷载传递效率变化是剪切强度差异的关键驱动因素。