Using air-cement-treated clay (ACTC) as a subgrade material for flexible pavements has gained widespread interest and acceptance. The mechanical properties of ACTC, including its compressive strength and elastic modulus (i.e., equivalent elastic modulus, Eeq\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$E_{{{\text{eq}}}}$$\end{document}) are required to realistically model its behavior in simulating pavement structure. This paper investigates the impact of different mixing proportions, particularly cement content and unit weight, on the mechanical properties of ACTC. These properties include its unconfined compressive strength (qu\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$q_{{\text{u}}}$$\end{document}) and elastic moduli (initial modulus (E0\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$E_{{0}}$$\end{document}), secant modulus (E50\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$E_{{{50}}}$$\end{document}), and Eeq\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$E_{{{\text{eq}}}}$$\end{document}). The aim of the current study is to develop an equation for estimating the Eeq\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$E_{{{\text{eq}}}}$$\end{document}, which is essential for analyzing pavement structures under cyclic loading. The study involves applying continuous monotonic and cyclic loads to evaluate the mechanical properties of ACTC mixtures with varying cement contents (35-135%) and controlled unit weights (8, 10, and 12 kN/m3). Our study findings indicate that both qu\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$q_{{\text{u}}}$$\end{document} and the elastic moduli are significantly influenced by cement content and unit weight, and are well described using the effective void ratio (est\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$e_{{{\text{st}}}}$$\end{document}) parameter. The ranges for qu\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$q_{{\text{u}}}$$\end{document}, E0\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$E_{{0}}$$\end{document}, and E50\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$E_{{{50}}}$$\end{document} were 51.9-411.2 kPa, 42.8-289.4 MPa, and 33.9-183.1 MPa, respectively. Eeq\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$E_{{{\text{eq}}}}$$\end{document} varied between 37.6 and 289.4 MPa, depending upon the cement content, unit weight, and applied stress level. Notably, Eeq\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$E_{{{\text{eq}}}}$$\end{document} values decreased with increasing vertical stress. A simplified equation, accounting for the combined effects of cement content and unit weight on the Eeq\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$E_{{{\text{eq}}}}$$\end{document} variation under different stress levels, is developed and recommended for practical use in designing ACTC mixtures for pavement analysis.

It has been well recognized that sand particles significantly affect the mechanical properties of reconstituted sandy clays, including the hosted clay and sand particles. However, interrelation between the permeability and compressibility of reconstituted sandy clays by considering the structural effects of sand particles is still rarely reported. For this, a series of consolidation-permeability coefficient tests were conducted on reconstituted sandy clays with different sand fractions (ass), initial void ratio of hosted clays (ec0) and void ratio at liquid limit of hosted clays (ecL). The roles of ass in both the relationships of permeability coefficient of hosted clay (kv-hosted clay) versus effective vertical stress (s0v) and void ratio of hosted clay (ec-hosted clay) versus s0v were analyzed. The results show that the permeability coefficient of reconstituted sandy clays (kv) is dominated by hosted clay (kv 1/4 kv-hosted clay). Both ass and ec0 affect the kv of sandy clays by changing the ec-hosted clay at any given s0v. Due to the partial contacts and densified clay bridges between the sand particles (i.e. structure effects), the ec-hosted clay in sandy clays is higher than that in clays at the same s0v. The kv - ec-hosted clay relationship of sandy clays is independent of ec0 and ass, but is a function of ecL. The types of hosted clays affect the kv of sandy clays by changing the ecL. Based on the relationship between permeability coefficient and void ratio for the reconstituted clays, an empirical method for determining the kv is proposed and validated for sandy clays. The predicted values are almost consistent with the measured values with kv-predicted=kv-measured 1/4 0.6-2.5. (c) 2025 Institute of Rock and Soil Mechanics, Chinese Academy of Sciences. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/ 4.0/).

Traditional water retention models often overlook the dynamic interplay between soil structure and moisture content, leading to inaccurate predictions of unsaturated soil behaviors. In this research, based on laboratory data, van Genuchten's soil water characteristic (van Genuchten, 1980) is modified to establish two bounding surfaces that define the permissible range of soil states in terms of the void ratio (e), suction (s), and degree of saturation (Sl). Considering a bounding surface technique, the model effectively captures hysteresis in the soil water retention behavior, encompassing main curves and scanning paths. This approach presumes that within the permissible range of soil states, which is included between two main surfaces, the derivative of the degree of saturation by void ratio and suction relies on the soil state's proximity to the main bounding surface. This hypothesis guarantees that the wetting-drying or compressing-swelling scanning curves transit smoothly toward their corresponding main surfaces. The derived equations for Sl are integrated into closed forms, allowing all scanning curves to be distinguished by varying values of the integration constant. Model necessitates the determination of two parameters (b and beta) related to the slope and intercept of the linear line interpolating experiments in the ln(s)-ln(eSl/s) plane, which can be defined based on at least a single wetting-drying test. The model predictions are validated against various data sets, including sands and clayey soils, published in the literature. This validation demonstrates the model's ability to reflect the behavior observed in experimental tests accurately. This new technique offers a significant advantage in the simplicity of parameter determination. Finally, this hysteretic water retention procedure is implemented into a finite element program (Code_Bright), and its performance is evaluated by simulating the behavior of a representative slope subjected to rainfall conditions.

This study presents some consolidated undrained triaxial compression (CU) tests of sand-low plastic silt (ML) mixtures, with ML contents of 0 %, 10 %, 20 %, 30 %, 40 %, and 50 %. The tests were performed on each mixture at three effective consolidation stresses (ECSs) of 50, 100, and 150 kPa. Triaxial testing equipment equipped with submersible local linear variable differential transformers (LVDTs) was employed to obtain accurate non-linear stiffness responses of the tested specimens over the course of the test. The testing results showed that the minimum and maximum void ratios (e min and e max ) of the specimens decreased until 20 % ML additions and then increased. Increasing the ECS of the test increased the deviatoric stress, contractive volumetric response and secant modulus (Eu) of all mixtures. Increasing the ML content at a given ECS decreased the deviatoric stress of the mixtures. The ML additions increased the excess pore water pressure (PWP) of the mixtures. The sand with low ML contents (0, 10, and 20 %) exhibited an initial contractive behaviour, followed by a dilative response. However, sand mixed with 30, 40, and 50 % ML were dominated by contractive response. The Euvalues of sand decreased with the ML additions. Consequently, these suggest that sand grains can retain their dilative nature and stability when the ML contents are low (i.e., sand-dominated soil matrix). However, when ML dominates the soil matrix, the mixtures exhibited a dominant contractive response with decreasing mean effective stress in their stress paths.

Using an energy-based approach and a wide range of marine silt content (SC), along with simulating different field conditions, a systematic experimental study was conducted through a series of strain-controlled cyclic triaxial tests on the undrained cyclic response of saturated Konarak carbonate sand-silt mixtures that originated from the northern coasts of the Oman Sea. The results revealed that the trend of variation in capacity energy (cumulative dissipated energy required to initiate liquefaction, Wliq) of sand-silt mixtures versus variation in SC was highly dependent on the relative density (Dr). Using the concepts of equivalent intergranular void ratio (e*) and equivalent interfine void ratio (ef*), a new relationship was proposed to estimate the Wliq of the Konarak sand-silt mixtures under different field conditions. To take into account the effects of SC, the energy-based pore water pressure model model proposed by Jafarian et al. (2012) was revised with modified calibration parameters. Similarly, as there exists a distinct relationship between energy dissipation and the excess pore water pressure generation during cyclic loading, a significant correlation is also observed between energy dissipation and stiffness degradation for carbonate soil.

The paper reviews the published literature on some aspects of fabric and particle behaviour in cohesionless soils. It uses insights from Discrete Element Modelling and Microcomputed Tomography to speculate on reasons for the difference in behaviour observed between moist tamped and sedimented sands at the same global void ratio and stress state. It is suggested that inhomogeneities in the form of macrovoids in moist tamped samples trigger localisation, collapse and the development of a local scale chain reaction. It questions whether a similar sequence applies at the field scale and whether expansive partial drainage influences the rate of propagation of the chain reaction. The paper offers reasons why the use of critical state based on moist tamped samples to assess the stability of tailings, may not be the best approach, and suggests that identifying instability lines for sedimented samples at appropriate void ratios and principal stress directions, may be preferable. Critical state reflects behaviour at large strains where initial and evolving inhomogeneities affect identification of relevant void ratios; instability lines reflect behaviour at small strains where inhomogeneities probably initiate collapse. The paper emphasises the importance of spatial variations in local void ratios in loose material, the importance of anisotropy of collapse potential and of load-controlled rather that strain-controlled shearing.

The artificial freezing method is commonly used in tunneling beneath overlying structures due to the significant development and utilization of underground space. However, there is a growing demand for controlling frost heave deformation in overlying structures and the interaction laws of these structures during freezing and undercutting remain unclear. Hence, a multi-physics coupling deformation calculation method is proposed. This study focuses on the shield tunneling project of Shanghai Metro Line 18 at Guoquan Road Station, which intersects with the existing upper operating station of Line 10. It investigates the construction approach for new tunnels during freezing, using the gray clay of layer ? 1 in Shanghai as the research target, particularly examining the disruptive effects on the primary structures of the upper operating station. Considering water migration, we derived the frost heave deformation formula and developed an improved thermo-hydro-mechanical coupling theory model by using pore ratio, freezing temperature, and average water pressure as coupling variables. Through frost heave tests on cohesive soil, we obtained the stress-strain relationship of frost heave specimens to describe the changes in pore structure. Subsequently, a thermo-hydro-mechanical three-field coupling numerical calculation was conducted using the weak form module (PDE) of COMSOL Multiphysics software. The simulation results closely matched the monitoring data and were below the predetermined control value, validating the accuracy of the enhanced coupling theory. These findings offer a multi-physics coupling approach for calculating deformations in similar frozen underpass tunnels, serving as a valuable reference for freezing method design and construction parameters. Additionally, we propose safety control indicators for reinforcement construction based on this scientific groundwork.

As urbanization accelerates and surface space becomes increasingly scarce, the development and utilization of urban underground space have become more critical. The sand-fine mixture soils commonly found in river-adjacent and coastal areas pose significant challenges to the design and construction of underground structures due to their unique mechanical properties. In soil mechanics, the minimum and maximum void ratios are crucial indicators for assessing soil compressibility, permeability, and shear strength. This study employed the discrete element method (DEM) to simulate the minimum and maximum void ratios of sand-fine mixtures under various conditions by setting six fine contents and three mean diameter ratios. The results indicate that as the fine content increases, these void ratios exhibit a trend of initially decreasing and then increasing, which can be effectively modelled using a single-parameter quadratic function. Additionally, the initial shear modulus was closely related to the uniformity of contact distribution at the microscopic level within the specimens. This study also introduced a dimensionless parameter that simultaneously described changes in contact distribution and initial shear modulus.

Under depressurization, the hydrate reservoirs undergo complex mechanical behaviors such as consolidation or shear. To deeply understand the evolution in the mechanical properties of soil, triaxial equipment with an ultrasonic system was used to detect the shear wave velocity in hydrate-bearing sediments. The effects of hydrate saturation, water, and stress state on shear-wave velocity are studied. The experimental results show that: The hydrate saturation significantly affects the wave velocity in the hydrate formation stage, while the water content has little influence on it. During the consolidation period, the notable increase in shear wave velocity indicates a decrease in soil void ratio, which means the soil has significant settlement deformation. With continuous shearing, the soil elastic modulus is damaged, and finally, the maximum damage can reach 35%. The conclusions can deepen understanding of the physical and mechanical properties of hydrate-bearing sediments in permafrost, and provide a reference for predicting the stratum stability during hydrate exploitation.

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.