Mechanical behavior and particle breakage of gap-graded coral sand-gravel mixtures under high pressure
WU Yang1, WANG Chuanzhi1, ZHANG Tao2*, LI Neng1, CUI Jie1
(1. School of Civil and Transportation Engineering, Guangzhou University, Guangzhou, Guangdong 510006, China; 2. School of Transportation and Civil Engineering, Nantong University, Nantong, Jiangsu 226019, China)
Abstract：The coral sand foundations in dredged and reclaimed foundations of South China Sea islands exhibit complex gradation characteristics, with localized strata presenting a sand-gravel mixture. This study investigates the particle breakage and shear characteristics of uniformly graded and gap-graded coral sand-gravel mixtures through a series of high-pressure drained triaxial tests. Experiments were conducted under varying confining pressures, gravel contents, and relative densities. Results demonstrated that gravel content and density significantly influenced the shear strength. Under low confining pressures, the stress-strain curves showed a steeper initial slope, which gradually moderated as the confining pressure increased. The peak principal stress ratio decreased with increasing effective confining pressure. Volumetric strains under high pressures exhibited contractive behavior, intensifying with higher confining pressures. The internal friction angle increased with relative density, peaking at 25% gravel content, while the corresponding apparent cohesion was minimized. Particle breakage intensified with rising confining pressure, and the evolution of particle size distribution followed a pattern characterized by an initially rapid transition followed by gradual stabilization. Furthermore, the peak principal stress ratio decreased progressively with an increase in the relative breakage index. A power function relationship is established between the peak mobilized friction angle and the relative breakage index. Finally, analysis of the stress-dilatancy relationship under high pressure revealed distinct mechanisms of dilatancy behavior under high- versus low-pressure conditions, highlighting the significant impact of gravel content. These findings provide theoretical support for the design and construction of dredged foundation engineering in island and reef environments.
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2026, Vol. 45 
