Effect of the quasi rate of loading in Particle Crushing and Engineering Properties of Black Tough Sand

In this study, the effect of the quasi-rate of loading in the crushing of tough black sand will be studied experimentally. The Black tuff sand was obtained from the Al-Hala area (Al Tafila) in southern Jordan. Sand chemical composition is composed mainly of SiO2 with a considerable amount of Fe2O3, Al2O3, and CaO oxides. The experimental works will be conducted at different normal stresses (136 kPa, 245 kPa, 463 kPa, and 899 kPa), different relative densities (20%, 40%, 60%, and 80%), and different rates of loading (0.50 mm/minute, 1.00 mm/minute and 2.00 mm/minute) using the direct shear tests. All test specimens were prepared with uniformly graded sand, passing United States standard sieve #4, and retained United States standard sieve #8. The results of direct shear tests were analyzed to examine the stress-strain response to different shearing rates and to obtain the shear strength parameters from the Mohr-Coulomb envelope to investigate the factors influencing shear strength parameters, especially the friction angles. After shearing each specimen, sieve analysis was performed to determine the extent of the percentage of particle breakage. Results showed that the rate of loading in direct shear tests plays a significant role in the amount of crushing and in the internal friction angles. The amount of crushing as well as shear strength was increased with the increased rate of loading. Moreover, the microstructural analysis used scanning electron microscopy (SEM) analysis showed that the crushing from granular has primarily resulted from disintegration, grinding, and abrasion of particles.