This study investigated the dynamic properties of red mud (RM)-reinforced volcanic ash (VA) by dynamic triaxial tests. The effects of stress state (dynamic stress sigma d, confining stress sigma 3), dynamic frequency (f) and load waveform (F) on the accumulative plastic strain (epsilon p) have been investigated. The findings indicate a significant influence of the stress state on epsilon p. When sigma d reaches 120 kPa, the specimens exhibit insufficient strength, leading to shear failure. As sigma 3 increases, the dynamic stresses that lead to specimen destabilization also exhibit an upward trend. The effect of f on epsilon p is limited. The epsilon p does not exhibit a clear or consistent developing pattern with increasing f. As for the F, the epsilon p exhibited by the specimens subjected to sinusoidal wave loads is less than that observed under trapezoidal wave loads. Shakedown theory classifies deformation responses into plastic shakedown, plastic creep and incremental collapse. The epsilon p curve patterns of RM-reinforced VA exhibit plastic shakedown and incremental collapse without significant plastic creep characteristics under cyclic loading. A predictive model for epsilon p under cyclic loading is established, which has good predictability. This study presents a novel application of VA and RM, offering substantial research insights into waste recycling.

Frozen soil is a common foundation material in cold region engineering. Therefore, the control and prediction of cumulative plastic strain for frozen soil materials are essential for the construction and long-term stability of actual foundation engineering under complex dynamic loadings. To investigate the influence of complex cyclic stress paths on frozen soil, a series of complex cyclic stress paths were conducted using the frozen hollow cylinder apparatus (FHCA-300).These cyclic stress paths included the triaxial cyclic stress path (TCSP), directional cyclic stress path (DCSP), circular-shaped cyclic stress path (CCSP), elliptical-shaped cyclic stress path (ECSP), and heart-shaped cyclic stress path (HCSP).The results indicated that the cumulative plastic strain under the five cyclic stress paths at three temperatures (-1.5,-6,and-15 degrees C) can be ranked as follows: DCSP>ECSP>HCSP>CCSP>TCSP. The cyclic stress paths are quantified based on the combined effects of the maximum shear stress (q(max)) and the principal stress axis angle (a). A developed model predicting cumulative plastic strain, considering complex cyclic stress paths, is introduced and demonstrates excellent predictive performance. The study's findings can offer insights into foundation engineering's deformation characteristics and settlement predictions under diverse complex dynamic loadings

Consolidated-drained true triaxial tests with constant b\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$b$$\end{document} values were performed on normally consolidated cross-anisotropic kaolin clay. Isotropic stress probes were incorporated into these true triaxial tests to study the orientations of plastic strain increment vectors and positioning of the plastic potential surface at different levels of shearing. An isotropic compression test was also performed to characterize the cross-anisotropic response of the clay. Pronounced cross-anisotropy was observed in the K0\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$K_{0}$$\end{document} consolidated kaolin clay during shear, particularly when the major and minor principal stresses were perpendicular and parallel to the axis of material symmetry, respectively. A simple rotational kinematic hardening mechanism incorporated into the single hardening constitutive model for soil has been found to fairly accurately simulate the evolution of anisotropy in the form of expansion and rotation of the yield and plastic potential surfaces during true triaxial shearing.

Dynamic triaxial tests were conducted to clarify the dynamic deformation characteristics of silty clay in flood irrigation areas under cyclic loading, using single-sample stepwise and multiple samples of constant amplitude. The effects of confining pressure, bias consolidation ratio, drainage conditions, dynamic load frequency, and cyclic stress ratio on the development law of cumulative plastic strain and residual dynamic pore pressure, the evolution characteristics of the hysteresis curve, and the change law of softening index of silty clay were studied. The results show that the development of cumulative plastic strain and residual dynamic pore pressure of soil under dynamic load is consistent. According to the stability theory, the dynamic behavior of samples under different test conditions can be divided into three typical cases: plastic stability, plastic creep and incremental failure. Under the basic conditions of this test, the boundary cyclic stress ratios of the three dynamic states of plastic stability, plastic creep, and incremental failure are around 0.30 and 0.40, respectively. The hysteresis characteristics of undrained specimens in the plastic stable state are obvious, and the hysteresis curve shows an S shape. With the progression of loading, soil experiences stiffness degradation. The cumulative plastic deformation of undrained specimens is smaller than that of drained specimens, and the softening index of soil under drained and undrained conditions remains stable at around 1.15 and 0.91, respectively, under lower cyclic stress ratios. Through grey relational analysis, it is found that the cyclic stress ratio has the greatest influence on the cumulative plastic strain and pore pressure ratio. The confining pressure exerts the greatest influence on the softening index. The parameters of the cumulative plastic strain model suitable for silty clay in flood irrigation areas have been determined, and the prediction effect is good.

The stability of geotechnical structures after an earthquake is primarily determined by the residual strength of surrounding soils that have not fully liquefied. This research employs the discrete element method (DEM) to study the undrained post-cyclic shear behaviour of sand under triaxial conditions, focusing on the effect of varying degrees of liquefaction (LD) simulated by subjecting the samples to different lengths of cyclic loading. Different types of cyclic loading, i.e. symmetric (fully reversal), partially reversal, and non-reversal ones, as well as the effect of sample density, have been considered. The results indicate that the samples under fully or partially reversal cyclic loading eventually liquefied, displaying a cyclic mobility failure mode. In contrast, samples under non-reversal cyclic loading develop plastic strain accumulation (PSA) failure without liquefaction. The post-cyclic shear stiffness of the samples is affected by both LD and the type of cyclic loading. For samples under reversal cyclic loading, the post-cyclic shear stiffness decreases as LD increases. Notably, the liquefied samples (LD = 1) initially exhibit near-zero stiffness during post-liquefaction shear until highly anisotropic force chains are formed along the loading direction, with their buckling leading to stiffness recovery. The length of the low-stiffness stage is influenced by the static shear stress and the relative density of the sample, which determines the rate of anisotropy accumulation during cyclic loading. The onset and completion of stiffness recovery are marked by a peak in anisotropy and an abrupt increase in effective anisotropy, respectively. For samples under non-reversal cyclic loading, the post-cyclic shear stiffness initially decreases with the increase in LD but increases at higher LDs due to the significant anisotropy developed during the cyclic loading stage.

Pisha sandstone (PS) rapidly collapses in water and its performance deteriorates seriously, and its special engineering properties have always been the focus of researchers. In areas where fillers are scarce, it is of great significance to use PS as roadbed fillers to slow down soil erosion and green environmental protection. However, the long-term deformation characteristics after construction need further study. To reveal the long-term dynamic characteristics of Pisha sandstone fillers (PSF) under vehicle load, this study conducted the cyclic loading test of PSF by using the GDS triaxial test system. The deformation characteristics of PSF under different cyclic stress ratios (zeta) and load frequencies (f) were studied. The grey correlation analysis method was used to obtain the correlation degree of each influencing factor to the cumulative plastic strain (CPS) of the PSF. Finally, the grey GM (1,1) model is used to predict the CPS data of PSF. Based on this, the classical semi-logarithmic strain model is modified, and the CPS prediction model of PSF is established. The results reveal that the zeta and f will promote the development of axial deformation of PSF. The axial elastic deformation (epsilon(e)) and CPS of PSF increase with the increase of zeta, and the zeta has a great influence on the CPS. The influence of f on epsilon(e) is more significant at high stress levels and less significant at low stress levels. The influence of f on CPS is opposite to that of epsilon(e), that is, the influence of high stress level is small, and the influence of low stress level is large. According to the degree of correlation, the factors are sorted according to the degree of influence: static strength (sigma(f)) > confining pressure (sigma(3)) > dynamic static stress ratio (eta) > load frequency (f) > cyclic stress ratio (zeta). The GM (1,1) model has high accuracy and reliability for the quantitative description and prediction of the CPS of PSF. At the same time, according to the test and GM (1,1) model prediction results, the CPS prediction model of PSF was established. The research can provide insights and references for the establishment of cumulative deformation and prediction model of PSF under cyclic loading.

In previous train operations, traffic loads were typically considered continuous, disregarding the intermittent effects of successive trains on subgrade loess. To investigate the cumulative plastic strain behavior and critical dynamic stress of subgrade loess under intermittent train loads, a series of dynamic triaxial tests were conducted considering factors such as cyclic stress ratio, confining pressure, and frequency. The deformation characteristics of subgrade soil under different stress levels were analyzed, and the dynamic behavior of specimens was categorized based on the development trends of strain rate and cumulative plastic strain. Then the critical dynamic stress levels for plastic shakedown and plastic creep states were determined. The results indicate that intermittent effects suppress the development of cumulative plastic strain and excess pore water pressure in the soil. The more cycles of the unloading-drainage stage the soil undergoes, the stronger its resistance to failure. Under intermittent loads, cumulative plastic strain increases with higher cyclic stress ratios and frequencies. When the cyclic stress ratio is constant, the increase in confining pressure enhances soil stiffness, but this increase is insufficient to counteract the strain induced by greater dynamic stress amplitude, resulting in increased cumulative strain. Combining cumulative plastic strain and plastic strain rate, a classification standard for the deformation behavior of subgrade loess under intermittent loading conditions was established, and the critical dynamic stress was identified. The critical dynamic stress increases with higher confining pressure but decreases with frequency. Accordingly, empirical formulas for critical dynamic stress concerning confining pressure and frequency were proposed. These findings are crucial for understanding the mechanism of intermittent train load effects and analyzing subgrade settlement.

This study investigates the evolution of the dynamic characteristics of a solidified dredge sludge, including the resilient modulus (MR), accumulative plastic strain (epsilon p) and damping ratio (lambda) during long-term traffic loadings considering influences of environmental actions (dry-wet, DW, and freeze-thaw, FT cycles), stress states (confining stress sigma cand deviator stress sigma d) and loading frequency (f). The experimental results indicate that the dynamic characteristics continuously change with increasing loading cycles and the influences of environmental actions, external stress state, and loading frequency are coupled. The resistance of the solidified sludge against traffic loading decreases after both DW and FT cycles, which is manifested by the decrease in the MR and the increase in the lambda and epsilon p. DW cycles induce greater reductions in the dynamic characteristics than the FT cycles. The increasing sigma c improves the resistance of the soil against cyclic loadings, resulting in higher MR and lower epsilon p and lambda. Besides, their rates of change with loading cycles (i.e., delta MR, delta epsilon p and delta lambda) reduce. The MR, epsilon p, lambda, and delta ap increase while the delta MR and delta lambda decrease with the sigma d, indicating that the increase in the cyclic loading level contributes to the accumulation of plastic strain and energy assumption while the resultant densification effect leads to the increase in the MR and decrease in the delta MR and delta lambda. The soil dissipates less energy when loaded under higher f, resulting in higher MR and lower epsilon p and lambda. Results reported in this paper are helpful for better understanding the dynamic responses of solidified sludge under complex loading and environmental conditions.

To investigate the impact of traffic loading on the deformation characteristics of soft dredger fill, a series of dynamic triaxial tests of soft dredger fill were carried out. The deformation characteristics of the soft dredger fill under varying confining pressures and dynamic stress ratios were analyzed comparatively. The test results indicate that the cumulative plastic strain curve of the soft dredger fill exhibits three distinct patterns: destructive, critical, and stable; Based on the cumulative plastic strain development law of the dredger fill, an empirical formula of critical dynamic stress and the prediction model of cumulative plastic strain development were established, considering the influence of confining pressure. Under continuous loading, the hysteresis curve of soft dredger fill showed pronounced non-linearity, and hysteresis. Initially, the curve exhibited an ellipse shape, transitioning to a crescent shape in the middle and late stages. The higher the dynamic stress ratio, the greater the height and width of the hysteresis loop. These findings provide valuable insights into the dynamic behavior of dredger fill under traffic loading.

This study examines the dynamic shear strength properties of expanded polystyrene lightweight soil (EPS LWS) samples through dynamic triaxial tests, focusing on the effects of EPS bead content, cement concentration, and confining pressure. The results indicate that increasing the cement content positively correlates with the dynamic strength of EPS LWS due to the formation of reticulate cement hydrates that bond soil particles. When the cement content is below 10%, EPS beads have minimal impact on dynamic shear strength. However, at cement contents of 15% or higher, increasing EPS bead content reduces dynamic strength because the low-strength EPS beads break under these conditions. Elastic deformation in EPS LWS remains stable, with elastic strain increasing as EPS particle content and confining pressure rise. This highlights the significant impact of these factors on elastic strain, which is crucial for achieving the desired density and strength in engineering applications. The nonlinear behavior under dynamic stress and strain, showing strain hardening at critical levels. Higher EPS content reduces the dynamic stress required for bearing capacity due to decreased stiffness. Additionally, the dynamic elastic modulus increases with cyclic loading frequency, while higher confining pressure enhances hoop stress effects, requiring more dynamic stress to achieve the same strain. This study provides insights into the dynamic shear strength properties of EPS LWS, emphasizing the critical roles of cement content, EPS bead content, and confining pressure in influencing its performance in engineering applications.