A comprehensive series of tests, including dynamic triaxial, monotonic triaxial and unconfined compressive strength (UCS) tests, were carried out on reconstituted landfill waste material buried for over twenty years in a closed landfill site in Sydney, Australia. Waste materials collected from the landfill site were treated with varying percentages of cement, and both treated and untreated specimens were investigated to evaluate the influence of cement treatment. The study examined the dynamic properties of cement-treated landfill waste, including cumulative plastic deformation, resilient modulus, and damping ratio, and also analysed the impact of cyclic loading on post-cyclic shear strength in comparison to pre-cyclic shear strength. The UCS tests and monotonic triaxial tests demonstrated that untreated specimens subjected to monotonic loading exhibited a progressive increase in strength with rising axial strain, whereas cement-treated specimens reached a peak strength before experiencing a decline. During cyclic loading, with the inclusion of cement, a significant reduction in cumulative plastic deformation and damping ratio was observed, and this reduction was further enhanced with increasing cement content. Conversely, the resilient modulus showed substantial improvement with the addition of cement, and this enhancement was further amplified with increasing cement content. The formation of cementation bonds between particles curtails particle movement within the landfill waste material matrix and prevents interparticle sliding during cyclic loading, leading to lower plastic strains and damping ratio while increasing resilient modulus. Post-cyclic monotonic testing revealed that cyclic loading caused the partial breakage of the cementation bonds, resulting in reduced shear strength. This reduction was higher on samples treated with lower cement content. Overall, the findings of the research offer crucial insights into the possibility of cement-treated landfill waste as a railway subgrade, laying the groundwork for informed design decisions in developing transport infrastructure over closed landfill sites while using landfill waste materials available on site.

It is generally believed that loess is not prone to liquefaction. However, on December 18, 2023, a magnitude 6.2 earthquake occurred in Gansu Province, China (35.70 degrees N, 102.79 degrees E), triggering a large-scale loess liquefactioninduced flow slide spanning 2.5 km, approximately 10 km from the epicenter. To understand the disastercausing mechanism, this study obtained the physical and mechanical properties of loess in the source area through field surveys and laboratory tests, and characterized the liquefaction behavior of saturated loess layers. The findings indicate that the strong ground motion, saturated loess, and gentle slope collectively contribute to the prevailing dynamic, geological, and topographic conditions. The saturated loess layer primarily comprises silt particles with particle sizes less than 0.075 mm accounting for approximately 92.2 % of its composition. The saturated loess layer at a depth of 11m was liquefied under the action of seismic waves with a peak ground acceleration of 0.40 g, however, due to the unique pore structure of loess, it is observed that pore pressure development rate lags behind strain rise rate during liquefaction process. The majority of strain accumulation occurred during a distinct post-peak stabilization phase following peak seismic activity while pore pressure continues to escalate even after vibration ceases. The results provide scientific insights into understanding the cause contributing to loess liquefaction induced-flow slide disasters due to earthquake.

A large diameter triaxial specimen of 61.9 mm was made by mixing coconut shell fibers with red clay soil. The shear strength of coconut shell fiber-reinforced soil was investigated using a dynamic triaxial shear test with confining pressure in a range of 50-250 kPa, a fiber content of 0.1%-0.5%, and a loading frequency of 0.5-2.5 Hz. The Hardin-Drnevich model based on the coconut shell fiber-reinforced soil was developed by analyzing and processing the experimental data using a linear fitting method, determining the model parameters a and b, and combining the influencing factors of the coconut shell fiber-reinforced soil to improve the Hardin-Drnevich model. The results show a clear distinction between the effects of loading frequency and fiber content on the strength of the specimens, which are around 1 Hz and 0.3%, respectively. Hardin-Drnevich model based on coconut shell fiber-reinforced soil can better predict the dynamic stress-strain relationship of coconut shell fiber-reinforced soil and reflect the dynamic stress-strain curve characteristics of the dynamic stress-strain curve coconut shell fiber-reinforced soil.

Cemented sand-gravel (CSG) is an innovative material for dam construction with a wide range of applications. Nevertheless, a comprehensive understanding of the dynamic properties of CSG is lacking. A series of cyclic triaxial dynamic shear tests were carried out on CSG materials to investigate their complex dynamic mechanical properties, leading to the establishment of a dynamic constitutive model considering damage. The findings indicate that both the application of confining pressure and the addition of cementitious material have a noticeable influence on the morphology of the hysteresis curve. Further research scrutiny reveals that augmenting confining pressure and gel content leads to an increase in the dynamic shear modulus and a decrease in damping ratio. Furthermore, a constitutive dynamic damage constitutive model was constructed by linking a damage element to the generalized Kelvin model and defining the damage variable D based on energy interaction principles. The theoretical formulas for dynamic shear modulus and damping ratio were adjusted accordingly. In addition, the stiffness matrix of the dynamic damage constitutive model was derived, which demonstrated its strong fitting effects in dynamic triaxial shear tests on CSG. Finally, the dynamic response and damage distribution in the dam body under dynamic loading were analyzed using a selected CSG dam in China.

As an emerging environmentally friendly solid waste-based composite foam lightweight soil, saponified slag fly ash (SS-FA) foam lightweight soil has a wide range of application prospects in road engineering. In this paper, the dynamic characteristics of SS-FA foam light soil material were investigated. Dynamic triaxial tests under different cyclic loading conditions were designed to analyze the variation rules of dynamic elastic modulus and damping ratio. The results showed that the stress-strain curve of SS-FA foam lightweight soil can be divided into three stages: elastic stage, plateau stage, and stress yielding stage. Under cyclic dynamic load, with the increase of dynamic stress amplitude, the dynamic elastic modulus of 400-700 kg/m3 samples gradually increased to the maximum, reaching 235.24 MPa, 324.54 MPa, 356.45 MPa, 379.67 MPa, respectively. The damping ratio, on the other hand, shows a tendency to first decrease and then slowly increase to stabilize. The dynamic elastic modulus is positively correlated with density grade, confining pressure and loading frequency. The damping ratio decreases with the increase of density grade and loading frequency, and increases with the increase of confining pressure. The electron microscope test was designed and image processing and data statistics were carried out. Through the grey correlation analysis, the correlation degree between the microstructure parameters of SS-FA foamed lightweight soil and the macroscopic mechanical properties is basically above 0.6, indicating that the two have a significant correlation. A normalized prediction formula model between the dynamic elastic modulus of materials and the conditional parameters was established. The R2 of the linear fitting of the predicted value is 0.964, indicating that the prediction model has a high degree of fitting and a good prediction effect. The research results revealed the dynamic mechanical properties of foamed lightweight soil, and provided a reference for the application of SS-FA foamed lightweight soil in subgrade engineering.

To establish the hysteresis model of EPS particles amended light weight soil under multi-step cyclic loading, the dynamic deformation characteristics of light weight soil were studied by consolidated undrained dynamic triaxial tests. The results showed that the backbone curve of light weight soil is hyperbolic and has strain hardening characteristics. With the increase of dynamic stress, the hysteresis curve shape of light weight soil gradually transforms from spindle-shaped to crescent-shaped, showing nonlinearity, hysteresis and strain accumulation. Based on the Hardin-Drnevich model and Masing rules, a modified unloading and reloading rule for the hysteresis model of light weight soil is proposed. The maximum dynamic shear modulus correction coefficient k1 and dynamic shear modulus attenuation coefficient k2 are introduced to establish the modified hysteresis model of light weight soil. Based on the modified hysteresis model, the physical meanings of k1 and k2 are defined. The influence of k1 and k2 values on the shape of hysteresis curve is discussed, and the empirical formulas of k1 and k2 about the dynamic shear strain are obtained. Through the verified dynamic triaxial tests of light weight soil by changing stress state, it is found that the relative error between the predicted values of modified hysteresis model and measured values is between 3.19% and 19.41%, which indicates that the model can describe closely the mechanical response process of light weight soil under complex dynamic conditions. The modified hysteresis model can predict the complex mechanical response mechanism in the progressive evolution of structural soil from convex to concave-convex hysteresis loop.

To assess the stabilizing effect of sodium alginate (SA) on cement soil subjected to dry-wet cycles, a comprehensive study was conducted involving UCS tests, dynamic triaxial tests, SEM analysis, and XRD analysis. The results showed that after 11 dry-wet cycles, the residual strength of the cement soil was 11.25 kPa with a 90.1% strength loss rate, while the SA-modified soil had a 72% loss rate and a residual strength of 432 kPa. Dynamic strain increased and dynamic elastic modulus decreased with higher dynamic stress, while higher loading frequencies reduced dynamic strain and increased dynamic elastic modulus. Increased cycle counts led to higher dynamic strain and lower dynamic elastic modulus. The damping ratio curves shifted downward with higher frequencies and moved rightward with more cycles. SEM and XRD analyses revealed that SA formed reticular cementitious materials that encapsulated soil particles and aggregated fines into larger particles. Sodium alginate significantly enhanced the soil's resistance to dry-wet cycles, providing valuable insights for coastal and soft soil subgrade engineering design.

A series of cyclic triaxial tests were conducted on marine soft clay deposits to establish and validate a predictive model for cumulative plastic strain. Additionally, a numerical model of particle flow code in cyclic triaxial tests was developed. The effects of confining pressure, moisture content, and dynamic stress ratio on the dynamic properties of marine soft clay were examined, considering factors such as volume deformation and microscopic failure patterns. The results indicated that both the predictive model and numerical model showed strong consistency with the experimental data. The plastic strain of marine soft clay was influenced by moisture content, stress ratio, and confining pressure in a consistent manner, with moisture content being the primary factor. A predictive model for the cumulative plastic strain of marine soft clay was successfully established, allowing for the evaluation of dynamic properties from the perspective of cumulative plastic strain. During the loading process in the numerical model, microcracks within the soil structure gradually compacted, and the main displacement of the specimen extended from the vertical center axis to the sides, ultimately resulting in shear damage.

This paper quantitatively analyses the macroscopic characteristics of soil hysteretic curves under dynamic loading and examines the elastic properties, viscosity, meso-damage degree and energy consumption of soil from a macroscopic perspective. Given the lack of research on the hysteresis characteristics of bioenzyme-modified silty soil, a series of dynamic triaxial tests were conducted under varying bioenzyme dosages, confining pressures, loading frequencies, and other conditions. The analysis focused on several parameters: the slope of the major axis of the hysteretic curve k, the ratio of the major to minor axes alpha, the distance between the central points of adjacent hysteretic curves d, and the area enclosed by the hysteretic curve S. These were used for quantitative analysis of the morphological characteristics, influencing factors, and changing patterns of the hysteresis curve in bioenzyme-modified silty soil. The results showed that the hysteresis curve of the bioenzyme-improved silty soil resembled an inclined ellipse. Under the influence of different bioenzymes dosages, confining pressures, and loading frequencies, k and alpha decreased as dynamic stress increased, while d and S increased exponentially with rising dynamic stress. When the bioenzyme dosage was 0.01%, the k value was largest, and alpha, d and S were smallest. With increasing confining pressure, k increased, while alpha, d, and S decreased. As the loading frequency increased, k, alpha, and d decreased, while S gradually increased. At a bioenzyme dosage of 0.01%, the bioenzyme had the greatest effect on improving the silty soil.

Silty clay is a common compressible soil found in many engineering projects, where its deformation behavior is particularly complex under cyclic loading. This study uses the GDS dynamic triaxial testing system to examine how silty clay deforms under different moisture contents, confining pressures, and cyclic stress ratios (CSR). The results show that the cumulative strain of silty clay follows a three-phase pattern: an initial rapid increase (N = 0-300), followed by a slower rise (N = 300-1000), and finally reaching a stable state (N > 1000). Among the factors tested, CSR has the most significant impact on cumulative strain, with moisture content coming second, while confining pressure has a relatively minor effect. After 1000 cycles, cumulative strain shows a clear linear growth trend. Linear fitting analysis indicates that the uncertainty in the fitted curve is influenced by moisture content, confining pressure, and CSR. Uncertainty is greater at both low and high moisture content levels, while it is lower under moderate moisture conditions. These findings provide valuable insights into predicting soil deformation in engineering applications, helping to improve our understanding of silty clay behavior under cyclic loading.