Breakage behavior of silica sands during high-pressure triaxial loading using X-ray microtomography

Particle breakage in sands can cause significant changes in particle-scale characteristics and is associated with many geotechnical engineering applications. The breakage behavior of loose silica sands sheared under high-pressure loading is studied using X-ray microtomography. Increases in confining pressure cause a significant strain hardening throughout the stress-strain curve, which is directly related to the successive particle breakage. A variety of particle-scale characteristics are quantitatively analyzed based on the CT images, including particle fracture, particle size, fractal dimension, particle shape, and coordination number. Splitting and chipping failure modes are more likely to occur by the external force bridging fewer particles. The fractal condition for particles smaller than 0.4 mm demonstrated that more breakage events occur in the smaller particles rather than larger particles. Particle shape shows an exponential relationship with the breakage indices regardless of the stress path. Meanwhile, the influence of particle breakage is more sensitive to sphericity and convexity than the aspect ratio. The evolution of the coordination number is quite size-dependent, and the larger particles tend to have a higher coordination number for all scans. In the shear stage, significant particle breakage causes a decrease in the mean coordination number, indicating that smaller particles with lower coordination numbers exist in the manner of filling the gaps between the larger particles.

Automated summary

Particle breakage in loose silica sands under high-pressure loading was studied using X-ray microtomography. Increases in confining pressure led to significant strain hardening and successive particle breakage. The analysis of CT images revealed various particle-scale characteristics and their relationships with breakage indices, including particle fracture, size, fractal dimension, shape, and coordination number. The results showed that splitting and chipping failure modes occurred by bridging fewer particles, and breakage events were more common in smaller particles. Particle shape had an exponential relationship with breakage indices, while the influence of breakage was more sensitive to sphericity and convexity than aspect ratio. The coordination number evolution was size-dependent, with larger particles having a higher coordination number, and significant breakage caused a decrease in mean coordination number during the shear stage.