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.

The real simulation of vehicle loads is the key to studying the dynamic behaviors of subgrade fill in cold regions. Considering the time interval between adjacent vehicles, a series of dynamic triaxial tests with continuous and intermittent cyclic loading were conducted. The results show that the intermittent effect of cyclic load can enhance the stiffness of frozen subgrade fill, which is also strengthened by the increasing intermittent stages and ratios. The initial dynamic shear modulus of frozen subgrade fill can be effectively described using a function that accounts for the intermittent stage and intermittent ratio. Furthermore, a relationship between the maximum shear stress and the initial dynamic shear modulus has been established. A modified HardinDrnevich model is proposed to consider the interaction between the dynamic shear modulus, the intermittent stage, and intermittent ratio. The damping ratio increases nonlinearly as the increasing dynamic shear strain and intermittent ratio. A shear strain threshold exists and is slightly affected by the intermittent stage, but it decreases with increasing intermittent ratio. When the dynamic shear strain is larger than the shear strain threshold, the damping ratio increases with the increase in intermittent stage. The research results can provide a guidance for further understanding of the dynamic properties of frozen subgrade fill under the actual vehicle loads.

This study investigates the mechanical properties and damage processes of cement-consolidated soils with Pisha sandstone geopolymer under impact loading using the Hopkinson lever impact test. The mechanical properties of cement-cured soils containing Pisha sandstone geopolymer were examined at various strain rates. The relationship between strain rate and strength of the geopolymer-cemented soil was established. As the strain rate increased, the coefficient of power increase for the Pisha sandstone geopolymer cement-cured soil initially rose before gradually stabilizing. The pore structure of the crushed specimens was analyzed using Mercury intrusion porosimetry. Based on the observed pore changes under impact loading, the pore intervals of the geopolymer-cemented soil were defined. A fitting model linking strain rate and porosity was developed. As strain rate increased, the porosity of the specimens first increased and then decreased, with larger internal pores gradually transforming into smaller ones. The highest porosity was observed at a strain rate of 64.67 s- 1. Crushing characteristics of the cement-cured soils under impact loading were determined through sieving statistics of the crushed particles. The average particle size of the fragments decreased as the strain rate increased. The fractal dimension initially decreased and then increased with the rise in strain rate, reaching its lowest value at a strain rate of 64.67 s- 1. Based on the dynamic mechanical properties, microscopic porosity, and fracture characteristics, the critical strain rate and damage form for cement-consolidated soils with Pisha sandstone geopolymer under impact loading were determined. This study offers valuable insights for the practical application of Pisha sandstone geopolymer cement-cured soils in engineering.

Unlike uniform soils, soft clays with sand interlayers in coastal soft clays, can affect their mechanical properties, potentially impacting underground-construction safety and stability. Consolidated undrained cyclic triaxial tests were conducted to study the dynamic properties and deformation behavior of clay, focusing on how the thickness ratio between the sand and clay layers and the cyclic-stress ratio influence the pore pressure, axial strain, shear-modulus ratio, and normalized damping ratio. The results indicate that higher thickness ratios and cyclic-stress ratios lead to a faster decay of the shear-modulus ratio, quicker increases in pore pressure, faster strain accumulation, and fewer cycles to failure. The normalized damping ratio has three different forms: decreasing, decreasing then increasing, and increasing. However, at a cyclic-stress ratio of 0.2 and thickness ratio of 0.25, the samples exhibit better dynamic characteristics. Soft clay with sand layers exhibits characteristics in line with the stability theory. At low thickness and cyclic-stress ratios, purely elastic and elastically stable phases are observed. As the thickness and cyclic-stress ratios increase, it transitions to plastic stability and incremental failure.

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 study investigates the cyclic response of unsaturated soils, focusing on the dynamic properties such as damping characteristics and soil stiffness, under varying matric suction and confining stress conditions during cyclic triaxial loading. Despite challenges in evaluating unsaturated soils compared to saturated ones, cyclic triaxial testing emerges as an efficient method for exploring their cyclic behavior. Through a series of experiments with different loading frequencies, stress levels, and suction conditions, the research reveals that as matric suction increases, stiffness rises while the damping ratio decreases. Additionally, comparisons between isotropic and anisotropic stress conditions show that the shear modulus is higher under anisotropic consolidation due to particle reorientation. The study proposes a semi-empirical equation to address the stress and suction dependency of shear modulus, finding a consistent trend between predicted and measured values. Ultimately, the findings underscore the significance of stress state, suction, cyclic shear strain, number of loading cycles and confining pressure in determining soil shear modulus.

The microstructure of a soil-rock matrix (SRM) is a determinant of its macroscopic physical and mechanical attributes. The influence of the shape and volume fraction (VF) of rock blocks on the dynamic properties of the SRM has not been subjected to quantitative analysis. Consequently, a suitable construction technique was developed for the fabrication of small-scale triaxial specimens incorporating artificial rocks of various shapes. A series of homogeneous SRM specimens with differing rock VFs and shapes were fabricated. These specimens were then exposed to a long-term dynamic load consisting of 15,000 cycles at a frequency of 1 Hz. The principal findings are summarized as follows: The construction method proposed is capable of producing small artificial rocks with dimensions of 3 mm or 5 mm in arbitrary shapes while maintaining consistency with the prototypes. The method holds significant promise for application in geotechnical testing. Under long-term dynamic loading, the rock VF effectively elevates the threshold cyclic stress ratio of the SRM, diminishes the Pore Water Pressure within the mixture, enhances the dynamic stiffness, and mitigates the cumulative strain. SRMs composed of rock shapes with increased angularity and reduced block sizes exhibit higher dynamic stiffness and cumulative strain. The threshold cyclic stress ratio for an SRM with a 40 % rock VF is approximately 0.04, and the pore pressure increment in the SRM exhibits a gradual change, which contrasts with the test outcomes for pure clay. The exponential-hyperbolic model provided a satisfactory fit for the pore pressure data, while the hyperbolic model yielded good fitting results for the cumulative strain of the SRM with a low rock VF. These findings contribute to an enhanced comprehension of the dynamic properties of railway subgrades filled with SRM under cyclic train loading conditions.

Dynamic properties of sandy soil under medium-high strain rates are of great significance for protection engineering, pile penetration, ship anchoring, aircraft landing, and so on. This paper reviews the current research status of split Hopkinson pressure bar (SHPB) impact tests and numerical simulations on sandy soil. The key issues in the research of sandy soil impact characteristics are summarized as follows: (1) The SHPB test still faces uncertainties for granular materials, such as the lack of standardized test sample size, difficulties in controlling boundary conditions, and the immaturity of triaxial testing methods. Future triaxial SHPB tests need to address issues related to measuring radial deformation of the samples and maintaining consistent confining pressure. (2) Due to uncertainties in gas and water discharge under test conditions and the presence of inertial effects, the accurate determination of strain rate effects becomes challenging. (3) The impact characteristics of granular materials are influenced by moisture content, which is correlated with changes in pore water pressure and pore air pressure. However, measuring these related variables is difficult, making it challenging to analyze the results. It is necessary to develop a device that completely eliminates the effects of gas and water discharge to mitigate the influence of boundary conditions. (4) To study the impact characteristics of sandy soils, it is necessary to overcome computational limitations and establish numerical models that account for complex mechanisms such as water content and particle fragmentation. Existing methods such as the finite element method, discrete element method, and coupled methods are unable to uniformly simulate the continuity of wave propagation and particle fragmentation. (5) It is crucial to develop constitutive models that consider the strain rate effects and can simulate complex mechanisms such as water content and particle fragmentation. This will refine the theoretical framework of soil mechanics at medium to strain rates.

Artificial ground freezing technology is the most important construction method of complex water-bearing soft clay rock. The thermodynamic properties of soft clay rock are important evidence for the design and construction of space resources development, and the variable hydrothermal parameter can directly affect the uncertain thermodynamic properties of soft clay rock. In this work, an array of field experiments on the soft clay rock are carried out, and the anisotropic spatial variations of hydrothermal parameters of soft clay rock are obtained. The statistical variability characteristics of variable hydrothermal parameters are estimated. A stochastic coupling model of soft clay rock with heat conduction and porous flow is proposed, and the uncertain thermodynamic properties of soft clay rock are computed by the self-compiled program. Model validation with the experimental and numerical temperatures is also presented. According to the relationship between anisotropic spatial variations and statistical variability characteristics for the different random field correlation models, the effects of the autocorrelation function, coefficient of variation, and autocorrelation distance of variable hydrothermal parameters on the uncertain thermodynamic properties of soft clay rock are analyzed. The results show that the proposed stochastic analysis model for the thermal characteristics of soft clay rock, considering the spatial variability of frozen soil layers, is scientifically reasonable. The maximum standard deviation of average thickness is 2.33 m, and the maximum average temperature is 2.25 degrees C. For the autocorrelation function, the most significant impact comes from DBIN. For the coefficient of variation, the most significant impact comes from thermal conductivity. Different variations of hydrothermal parameters have different effects on the standard deviation of soft clay rock temperature. The biggest influence is the thermal conductivity, while the lowest influence is the specific heat capacity.

Assessing the subsurface geological conditions beneath a structure is crucial, as soils inherently tend to lose intergranular strength when subjected to static or dynamic loads. Applying dynamic loads can result in the propagation of stress waves through the soil, leading to deformation of the soil structure and causing more significant damage than static loads. Extensive research has been conducted on treating dynamic characteristics of clay soil properties using traditional additives such as lime and cement. To achieve better results and address the limitations of conventional materials in soil improvement, there is a growing trend towards using nontraditional stabilizers, referred to as 'recycled and sustainable' materials. These include, for example, silica fume, polypropylene fibers, steel slag, fly ash, rubber tire particles, basalt, and recycled and crushed glass, which are currently being deeply investigated to improve the dynamic behavior of clay soils. The review article compares the effects of traditional and sustainable stabilizers on dynamic engineering properties of soils. It also highlights the engineering significance and innovations in the use of such materials. While traditional stabilizers effectively improve soil strength and durability, they pose environmental challenges, including increased CO2 emissions and brittleness under seismic stress. Innovations focus on refining these techniques and incorporating sustainable alternatives, such as waste-derived materials, to enhance soil properties, improve seismic performance, and reduce environmental impact. The study underscores the need for developing cost-effective, ecofriendly solutions for modern infrastructure. It systematically analyzes recent topics on soil stabilization using these additives, examining parameters that influence the dynamic properties of stabilized clay soils. Furthermore, it reviews microstructural changes due to stabilization and their impact on dynamic properties, offering suggestions for future research.