Shear characteristics of calcareous gravelly sand considering particle breakage

Calcareous sand is a special geomaterial susceptible to breakage. In this study, calcareous gravelly sand (CGS) was subjected to multiple consolidated-drained triaxial shear tests under different relative densities (Dr) and effective confining pressures (σ3′\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${\sigma }_{3}^{^{\prime}}$$\end{document}). The purpose was to investigate the effects of particle breakage on the shear characteristics of calcareous sand. According to the results, the strain-softening and dilatancy characteristics of CGS gradually weakened with increasing σ3′\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${\sigma }_{3}^{^{\prime}}$$\end{document} and decreasing Dr. Within σ3′\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${\sigma }_{3}^{^{\prime}}$$\end{document} ≤ 400 kPa, the peak-state friction angle (φp) of calcareous sand collected from the island-reefs in the South China Sea had a range of 37.8–62.9°. Moreover, φp decreased with increasing σ3′\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${\sigma }_{3}^{^{\prime}}$$\end{document} and decreasing Dr. A physical model was built to predict the secant modulus (E50) of CGS based on its Dr and σ3′\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${\sigma }_{3}^{^{\prime}}$$\end{document}. Particles 1–2 mm in size had the largest breakage extent, and mainly broke into particles of 0.5–1 mm and 0.075–0.25 mm. The applicability of inverse proportional function for describing the relationship between plastic work and relative breakage ratio for CGS was validated. Neither Dr nor σ3′\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${\sigma }_{3}^{^{\prime}}$$\end{document} greatly affected their relationship. Increasing particle breakage weakened the strain-softening and dilatancy characteristics of CGS and reduced its φp but enhanced its deformation resistance. The findings of this study provide a theoretical basis for infrastructure construction on the island-reefs in the South China Sea.