For noncrushable sand, this paper describes the experimental phenomenon of the opposite turning directions of stress-dilatancy curves between sands before and after cementation. Then, based on the thermomechanical framework and Legendre transformation, the stress-dilatancy model is obtained from the dissipation function. This stress-dilatancy model considers the coupled effect of bond breakage and rearrangement energy. This model also incorporates the mechanism that cementation-improved strength leads to the opposite turns of sands before and after cementation. Compared with the other four existing stress-dilatancy models, this paper's model can depict the opposite turning directions of stress-dilatancy curves between uncemented and cemented sands. This stress-dilatancy model is also verified through five types of cementation: colloidal-silica-cemented sand, (CaCl2+Na2SiO3) cemented sand, naturally bonded sand, microbially induced carbonate precipitation (MICP)-cemented sand, and portland cement-treated sand. The broader application of the model is that it can also be used for crushable sand with particle breakage, as well as artificially cemented sand after freeze-thaw damage.

Laboratory tests on undisturbed and remolded Shanghai clay were conducted with a novel mixed boundary true triaxial apparatus. The strength and deformation behaviors of the structured soft clay at different Lode angles were carefully investigated. The relationship between the shear stress ratio and the dilatancy ratio of the clay in three different stress spaces, that is p-q space, transformed stress (TS) space, and tij modified stress space, is discussed in detail. In particular, the influences of the stress path and the structure of nondisturbed clay on the strength, deformation, and failure criterion of Shanghai clay were quantitatively evaluated. The shear strength and dilatancy of undisturbed/remolded clay decreases with the increase of the Lode angle. It is also found that the shear strength and dilatancy of the undisturbed clay are larger than those of the remolded clay, while the influence of the structure on the dilatancy decreases with an increase in the Lode angle. In the pi-plane, the maximum strength of Shanghai clay under different stress paths generally obeys the spatial mobilized plane failure criterion. The coincidence of the stress-dilatancy relationship given by the TS and tij stress spaces with the test results is much better than that given by p-q stress space. Furthermore, the linearity of the plastic potential curves of the undisturbed/remolded clay is more evident in tij stress space.

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.

This study investigates the effect of a stress state change at an intermediate stage during cyclic loading on the drained cyclic deformation of soil using Discrete Element Method (DEM) simulations. Drained cyclic triaxial simulations were conducted on an assembly of irregularly shaped particles, with the stress state shifting along different stress paths at an intermediate stage of cyclic loading. The analysis of the macro- and microscopic responses reveals a link between the cyclic stress-dilatancy behaviour and the anisotropy of the granular assembly. In the simulations without the stress state change or with a stress ratio increase, the strain accumulation direction aligns with the prediction of the Modified Cam Clay (MCC) flow rule; and the strain accumulation is faster at higher stress ratios when the contact distribution is more anisotropic. However, when the particle assembly experiences a stress ratio decrease during cyclic loading, the subsequent strain accumulation direction deviates from the MCC flow rule, and strains accumulate more rapidly at lower stress ratios when the contact distribution is nearly isotropic. A tentative explanation is proposed to explain the altered strain accumulation direction after the stress ratio decrease.

Waste disposal has become a major challenge due to the increasing production driven by urbanization. Two such wastes generated in substantial quantities are steel slag and construction and demolition waste (CDW). The current study explored the stress-dilatancy and critical-state behaviors of geogrid-reinforced recycled steel slag and CDW for evaluating its suitability in various geotechnical applications. A set of consolidated drained triaxial tests were carried out on test samples, with and without geogrid reinforcement, to achieve this objective. The performance of the steel slag and CDW material was compared with that of commonly used geomaterial, namely, sand. Steel slag exhibited higher strength compared to sand and CDW. At a confining stress of 50 kPa, the strength of steel slag was 1.6 times greater than that of sand, while the strength of CDW was 1.3 times higher than that of sand. The effect of geogrid reinforcement on stress-dilatancy and critical-state behavior was quantified for all the materials. Results revealed that the critical-state line rotates in a clockwise direction in the presence of the geogrid. On the other hand, the stress-dilatancy curve of the materials shifted upward with the inclusion of the geogrid. At a confining pressure of 50 kPa, the peak dilation angles of reinforced sand, slag, and CDW were 0.8, 0.7, and 0.9 times that of the unreinforced specimens, respectively. In addition, the strength properties, energy absorption capacity, and modulus degradation of the materials were also evaluated. A mathematical expression was proposed to relate the energy absorption capacity of the geogrid-reinforced materials with the critical-state stress ratio. Moreover, the Li and Dafalias stress-dilatancy model parameters were proposed to capture the stress-dilatancy behavior of the materials. Overall, encouraging performance of the waste materials was observed for potential geotechnical applications.

The present study is devoted to the investigation of the dilatancy behaviour of a fine sand based on hollow cylinder tests. Medium and dense samples were tested at a constant average stress by applying torsional angles for shear strains gamma = 1, 2, 3 and 4%. Dilatancy curves along with shear wave velocity measurements to investigate the influence of the shear strain amplitude gamma(ampl) in the shear modulus degradation curve are presented and discussed. The measured stress and strain paths were used to compare the performance of four advanced constitutive models especially in describing the dilatancy behaviour of sand. From the perspective of their constitutive equations, the differences between the simulations with various material models are examined. It may be concluded that all four models allow a proper prediction of torsional shear tests as long as a proper calibration of the material parameters is secured.