The role of incremental stress ratio in mechanical behavior and particle breakage of calcareous sand

Calcareous sand has been used in reclamation for constructing artificial islands. It suffers different stress paths with varying constant incremental stress ratios (Delta q/Delta p'), exhibiting diverse mechanical characteristics with grain crushing. However, previous experimental studies mainly focused on conventional triaxial stress path (Delta q/Delta p' = 3). This study aims to investigate more unconventional shear stress paths, such as constant ratios of Delta q/Delta p' (=-0.5,-1.5,2\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ = -0.5, \, -1.5, \, 2$$\end{document}, where negative ratio corresponding to p'-decreasing, and vice versa) and constant p' (Delta q/Delta p' = infinite) on both anisotropically and isotropically consolidated calcareous sand. For comparison, the conventional triaxial tests under constant confining pressure (Delta q/Delta p' = 3) are also performed. For all tested samples, the grain size distribution is measured to quantify the particle breakage after loading. It is found that shear stress path plays a significant role in the mechanical of calcareous sand. Despite varying degrees of particle breakage caused by different stress paths, the relationship between the peak state friction angle with the maximum dilatancy angle and state parameter is unique. Irrespective of the consolidation/shear stress path, the peak friction angle consistently exhibits a monotonic increase with the maximum dilatancy angle, while exponentially decreases with the increasing of state parameter. Additionally, particle breakage causes a downward curvature of the critical state line (CSL) in the e-lnp' plane. However, irrespective of the stress path, the CSL remains linear when plotted in e-(p'/pa)xi and the e-ln(p' + pr) plane. The findings are helpful for understanding the mechanical behavior and modeling of crushable calcareous sand under complex loads.