Frozen mixed soils are widely distributed in the strata and slopes of permafrost regions. This paper aims to study the strength criterion and elastoplastic constitutive model for frozen mixed soils from micro to macro scales. Based on the knowledge of mathematical set theory and limit analysis theory, the support function of frozen soils matrix is derived. The concept of local equivalent strain is proposed to solve the problem of nonuniform deformation caused by rigid inclusions in frozen mixed soils. According to the nonlinear homogenization theory and the Mori-Tanaka method in micromechanics, the strength criterion of frozen mixed soils is established, which can consider coarse particle contents. By introducing the concepts of equivalent yield stress and equivalent plastic deformation, the elastoplastic constitutive model is proposed by the associated flow rule, which can also consider the influence of coarse particle contents. Finally, using the data in the literature, the proposed strength criterion and elastoplastic constitutive model for frozen mixed soil are verified, respectively. The effects of coarse particle contents on the mechanical properties of frozen mixed soils are discussed.

Due to the development of plastic strains, the strain path within the meridian plane deviates from the reference line corresponding to elastic state. Similarly, under true triaxial stress conditions, the strain path within the deviatoric plane deviates from the reference line corresponding to the constant Lode angle. This deviation is attributed to the plastic shear strain associated with the Lode angle. To account for these phenomena, a novel three-dimensional elastoplastic constitutive model incorporating Lode angle is proposed to characterize the deformation behavior of sandstone. The yield and potential functions within this model incorporate parameters that vary with the plastic internal variable, enabling the evolution of the yield and plastic potential surfaces in both the meridian and deviatoric planes. The comparison between experimental data and the analytic solution derived from the constitutive model validates its reliability and accuracy. To examine the differences between yield surface and plastic potential surface, a comparison between the associated and non-associated flow rules is conducted. The results indicate that the associated flow rule tends to overestimate the dilatancy of sandstone. Furthermore, the role of Lode angle dependence in the potential function is explored, highlighting its importance in accurately describing the rock's deformation.

Intelligent compaction (IC) technology based on the continuous compaction control (CCC) technology enables real-time monitoring, evaluation, and feedback of compaction quality. However, the lack of a viscoelastoplastic constitutive model of hot asphalt mixture under triaxial stress states, as well as the difficulty in simulating the time-varying characteristics of material properties, hinders the research and application of IC in asphalt concrete (AC) layers. Therefore, this paper proposes a viscoelastoplastic constitutive model for AC20 asphalt mixture and establishes a vibrating compaction numerical model for time-varying characteristics in material properties using finite-element modeling (FEM) analysis software Abaqus. Additionally, the stress state of the pavement was analyzed, and adjustment methods for vibrating compaction technology are proposed to further improve the compaction quality of the AC lower surface layer. Subsequently, the intelligent compaction measurement values (ICMVs) were calculated according to the acceleration and displacement response of the roller, and the reasons for the change in ICMVs were determined. Field test results verified that the established numerical model can realistically simulate the mechanical behavior of asphalt pavement under actual vibrating compaction conditions, thus providing a theoretical basis for the application of IC feedback control technology in AC lower surface layer.

This paper investigates shear banding as a possible failure mode for silt-clay transition soils under general three-dimensional stress conditions. Drained and undrained true triaxial tests with constant b values were performed on tall prismatic specimens of such soils with systematically varying silt contents. Based on the values of critical plastic hardening modulus, shear banding does not govern the strength characteristics of the soils for b values less than 0.2. For larger b values, shear band formation is essentially critical as it takes place in the hardening regime of the stress-strain curves prior to the smooth peak failure points. An increase in silt content appears to move the onset of shear banding to lower levels of shear in the stress-strain relations of the silt-clay transition soils. It is also demonstrated that a non- associated constitutive model with a single hardening law is capable of accurately predicting the onset of shear banding in normally consolidated silt-clay transition soils based on bifurcation theory. (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- NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

Considering fabric evolution effects is crucial for accurately describing the macroscopic mechanical behavior of cohesionless soil under cyclic loading. Building upon the nonlinear dilatancy equation established for sand-gravel composites under monotonic loading, a fabric-dilatancy internal variable, which accounts for fabric evolution during the dilatancy stage under cyclic loading, is introduced. An elastoplastic constitutive model based on the generalized plasticity framework is proposed to capture the full range of mechanical behaviors of sand-gravel composites under both static and liquefaction conditions. By comparing the liquefaction deformation, stress paths, and excess pore water pressure development of sand-gravel composites before and after considering fabric evolution effects, the significance of fabric evolution effects in simulating the liquefaction response of sand-gravel composites is demonstrated. The model's performance is validated through a series of large-scale triaxial tests on sand-gravel composites under both static and dynamic loading conditions, as well as by comparing with test results from relevant literature. The results show that the model generally provides a reasonable representation of the stress-strain-volume behavior of sand-gravel composites under static drained conditions, as well as the accumulation and dissipation of excess pore water pressure, stress path evolution, and liquefaction deformation during liquefaction. This model can serve as a powerful tool for numerical simulation in sand-gravel composites engineering.

The structure of unsaturated loess has a significant impact on its hydraulic and mechanical properties. An elastoplastic model considering the structured evolution of unsaturated loess is presented in this paper using double stress variables consisting of average skeleton stress and suction. The model divides the structure of unsaturated loess into inherent structure and suction-induced structure from the structured composition of loess and gives isotropic compression equation for unsaturated loess that considers the structure evolution. At the same time, a soil-water characteristic curve considering the influence of the void ratio is introduced to reflect the coupling between the hydro-mechanical behaviours of unsaturated loess. The proposed isotropic compression equation is extended to axisymmetric stress space with the aid of the yield surface and flow law in the modified Cam-clay model. The proposed model can not only reflect the structured evolution of loess, but also predict reasonably the mechanical and hydraulic behaviour of loess under different stress paths. The reasonableness and availability of the proposed model are initially verified by comparison with the results of the unsaturated loess isotropic compression tests at constant suctions, the wetting test at constant net stresses, the complex stress path tests and the triaxial shear tests as well.

A comprehensive three-dimensional elastoplastic constitutive model is presented to characterize the stress-strain behavior of cement stone under the true triaxial stress state. This constitutive model incorporates a threedimensional yield function and a three-dimensional potential function. The three-dimensional yield function is designed to accurately represent the true triaxial stress state during hardening. The three-dimensional potential function is devised to depict the plastic flow direction under true triaxial stress state. The yield and potential functions include parameters that control the shape of the deviatoric and meridian planes, and these parameters vary with the plastic internal variable. Consequently, the yield function can accurately describe the stress state, and the potential function can precisely capture the variations in plastic flow direction. Additionally, a detailed procedure for determining the parameters of the yield function and potential function is proposed based on the full deformation process. The constitutive model is presented in the form of analytical solution. The comparison of experimental data with the constitutive model confirms its accuracy and validity. A sensitivity analysis of the deviatoric and meridian parameters in the potential function is performed, shedding light on their impact on the model behavior. Furthermore, the significance of incorporating Lode angle dependence into the potential function is discussed, emphasizing its essential role in accurately capturing strain in the direction of the intermediate principal stress.