Understanding accurately the influence of non-plastic fines on stress-dilatancy of coral sand mixture-packing is crucial for marine engineering in various geotechnical applications. This work experimentally examined the effects of non-plastic fines and initial test conditions on stress-dilatancy behavior of mixture. Based on test results, equivalent void ratio (e*\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${e}{*}$$\end{document}) was determined to quantify the global effect of fines on shear behavior across different shear stages. Test results show that e*\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${e}{*}$$\end{document} exhibits a reduction as the mean effective stress (p '\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${p}{\prime}$$\end{document}) increases, following a power function relationship. Besides, e*\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${e}{*}$$\end{document} variation under phase transformation, peak state, and critical state can be described by a normalized curve. Reduced fines content and increased relative density can contribute to the enhancement of both peak strength and internal friction angle within the mixture. However, the smooth shape and lubrication function facilitated by fines actively contribute to initiation of shear contraction. Furthermore, the stress paths observed in the CD shear tests manifest as a sequence of parallel straight lines within the q\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$q$$\end{document}-p '\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${p}{\prime}$$\end{document} plane. The length of these lines progressively extends as the stress level escalates. Moreover, deviator stress in q\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$q$$\end{document}-p '\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${p}{\prime}$$\end{document} curves under character state presents lower and upper limits which are 0.334 and 0.639 corresponding to tested samples determined by fines content and relative density. Elevated fines content combined with reduced relative density can lead to a reduction in both peak-state friction angle and maximum angle of dilation.

The naturally deposited soil usually does not consist of pure coarse or fine-grained soil but of a mixture of both. The mechanical behaviour of a saturated fine sand mixed with varying amounts of low-plastic fines was evaluated by monotonic as well as high-cyclic triaxial tests. The test results were used to conclude on the effect of fines content on the critical state, phase transformation line, secant Young's modulus, the residual strain accumulation as well as strain amplitude during drained cycles of the mixtures in relation to the global void ratio as well as to the equivalent void ratio. It was found that while the choice of void ratio definition is important for the uniqueness of the critical void ratio, both approaches can be used as state variables for the phase transformation line. However, some seemingly contradictive results are found from the drained high-cyclic tests. Eventhough, an increase of the residual strain accumulation with decreasing fines content compared at the same initial equivalent void ratio is rendered by the laboratory data, a unique and on fines content independent relationship between eacc could be established only with respect to the initial global void ratio.

Case histories from at least 28 earthquakes worldwide have indicated that liquefaction can occur in gravelly soils (both in natural deposits and manmade reclamations), inducing large ground deformation and causing severe damage to civil infrastructures. However, the evaluation of the liquefaction potential and cyclic strain accumulation characteristics of gravelly soils remains a major challenge in geotechnical earthquake engineering. To provide new and useful insights into this crucial topic, stress -controlled undrained cyclic triaxial tests were conducted on sand -gravel mixtures (SGM) having sand -dominated microstructure but different packing states (i.e., soil grain arrangement), which were obtained by varying the gravel content (GC) and relative density (Dr). The experimental results confirmed that both the GC and Dr have marginal (at low GC and Dr) to significant (at high GC and Dr) effects on the cyclic resistance ratio (CRR) of SGM, but highlighted the need to consider GC and Dr effects together. In this regard, the use of state parameters, such as the equivalent void ratio (ef(eq)) and equivalent relative density (Drf(eq)), were found to be suitable approaches to describe the combined effect of GC and Dr on CRR as they provide unique correlations for sand -dominated SGM irrespective of their packing states. (c) 2024 Production and hosting by Elsevier B.V. on behalf of The Japanese Geotechnical Society. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).