There has been a growing interest in controlled low strength material CLSM due to its engineering features, such as self-leveling and early strength development, as well as it potential for utilizing industrial waste. Still, the dynamic properties on CLSM are rarely studied. This study evaluates the feasibility of red mud as a partial aggregate replacement in foamed-lightweight CLSM, incorporating high-carbon fly ash and preformed foam. We varied both the red mud contents RMc and foam volume ratio FVR within the mixtures and examined their impact on unconfined compressive strength and dynamic properties including shear modulus G and damping ratio D. The results reveal that the red mud enhances foam stability, leading to more uniform pore structures and increased porosity, which reduces bulk densities. Despite higher porosity, red mud serves as a strong alkaline activator, enhancing geopolymer reactions of high-carbon fly ash and thereby increasing both compressive strength and initial shear modulus G0. Interestingly, increasing FVR had minimal impact on the D, while higher RMcnotably increased D, highlighting its distinct role in energy dissipation. The red mud-incorporated foamed CLSM exhibits strain-dependent normalized shear modulus G/G0 comparable to that of gravel, while its D is 40-100 % higher than gravel or gravelly soil at shear strain of 1.10-5, which corresponds to typical traffic-induced vibration levels. Moreover, theoretical volumetric-gravimetric relationships are introduced to account for the combined effects of FVR and RMcon CLSM behavior. These findings demonstrate that the red mud included foamed CLSM can be utilized as advanced structural backfill material capable of effectively mitigating the vibrations induced by traffic, low-amplitude seismic events, and mechanical sources.

This study investigates the microhardness and geometric degradation mechanisms of interfacial transition zones (ITZs) in recycled aggregate concrete (RAC) exposed to saline soil attack, focusing on the influence of supplementary cementitious materials (SCMs). Ten RAC mixtures incorporating fly ash (FA), granulated blast furnace slag (GBFS), silica fume (SF), and metakaolin (MK) at 10 %, 15 %, and 20 % replacement ratios were subjected to 180 dry-wet cycles in a 7.5 %MgSO4-7.5 %Na2SO4-5 %NaCl solution. Key results reveal that ITZ's microhardness and geometric degradation decreases with exposure depth but intensifies with prolonged dry-wet cycles. The FAGBFS synergistically enhances ITZ microhardness while minimizing geometric deterioration, with ITZ's width and porosity reduced to 67.6-69.0 mu m and 25.83 %, respectively. In contrast, FA-SF and FA-MK exacerbate microhardness degradation, increasing porosity and amplifying microcrack coalescence. FA-GBFS mitigates the diffusion-leaching of aggressive/original ions and suppresses the formation of corrosion products, thereby inhibiting the initiation and propagation of microcracks. In contrast, FA-SF and FA-MK promote the formation of ettringite/gypsum and crystallization bloedite/glauberite, which facilitates the formation of trunk-limb-twig cracks.

Accurately modeling soil-fluid coupling under large deformations is critical for understanding and predicting phenomena such as slope failures, embankment collapses, and other geotechnical hazards. This topic has been studied for decades and remains challenging due to the nonlinear responses of geotechnical structures, which typically result from plastic yielding and finite deformation of the soil skeleton. In this work, we comprehensively summarize the theory involved in the soil-fluid coupling problem. Within a finite strain framework, we employ an elasto-plastic constitutive model with linear hardening to represent the solid skeleton and a nearly incompressible model for water. The water content influences the behavior of the solid skeleton by affecting its cohesion. The governing equations are discretized by material point method and two sets of material points are employed to independently represent solid skeleton and fluid, respectively. The proposed method is validated by comparing simulation results with experimental results for the impact of water on dry soil and wet soil. The capability of the method is further demonstrated through two cases: (1) the impact of a rigid body on saturated soil, causing water seepage, and (2) the filling of a ditch, which considers the erosion of the foundation. This work may provide a versatile tool for analyzing the dynamic responses of fluid and solid interactions, considering both mixing and separation phenomena.

In geotechnical engineering, the development of efficient and accurate constitutive models for granular soils is crucial. The micromechanical models have gained much attention for their capacity to account for particle-scale interactions and fabric anisotropy, while requiring far less computational resources compared to discrete element method. Various micromechanical models have been proposed in the literature, but none of them have been conclusively shown to agree with the critical state theory given theoretical proof, despite the authors described that their models approximately reach the critical state. This paper modifies the previous CHY micromechanical model that is compatible with the critical state theory based on the assumption that the microscopic force-dilatancy relationship should align with the macroscopic stress-dilatancy relationship. Moreover, under the framework of the CHY model, the fabric anisotropy can be easily considered and the anisotropic critical state can be achieved with the introduction of the fabric evolution law. The model is calibrated using drained and undrained triaxial experiments and the results show that the model reliably replicates the mechanical behaviors of granular materials under both drained and undrained conditions. The compatibility of the model with the critical state theory is verified at both macroscopic and microscopic scales.

Liquefaction resistance and post-liquefaction shear deformation are key aspects of the liquefaction behavior for granular soil. In this study, 3D discrete element method (DEM) is used to conduct undrained cyclic triaxial numerical tests on specimens with diverse initial fabrics and loading history to associate liquefaction resistance and post-liquefaction shear deformation with the fabric of granular material. The influence of several fabric features on liquefaction resistance is first analyzed, including the void ratio, particle orientation fabric anisotropy, contact normal fabric anisotropy, coordination number, and redundancy index. The results indicate that although the void ratio and anisotropy strongly influence liquefaction resistance, the initial coordination number or redundancy index can uniquely determine liquefaction resistance. Regarding post-liquefaction shear deformation, the above quantities do not dictate the shear strain induced after initial liquefaction. Instead, the mean neighboring particle distance (MNPD), a fabric measure previously introduced in 2D and extended to 3D in this study, is the governing factor for post-liquefaction shear. Most importantly, a unique relationship between the initial MNPD and ultimate saturated post-liquefaction shear strain is identified, providing a measurable state parameter for predicting the post-liquefaction shear of sand.

The present paper sets out a comparative analysis of carbon emission and economic benefit of different performance gradients solid waste based solidification material (SSM). The macro properties of SSM were the focus of systematic study, with the aim of gaining deeper insight into the response of the SSM to conditions such as freeze-thaw cycles, seawater erosion, dry-wet cycles and dry shrinkage. In order to facilitate this study, a range of analytical techniques were employed, including scanning electron microscopy (SEM), X-ray diffraction (XRD) and mercury intrusion porosimetry (MIP). The findings indicate that, in comparison with cement, the carbon emissions of SSM (A1) are diminished by 77.7 %, amounting to 190 kg/t, the carbon-performance ratio (24.4 kg/ MPa), the cost-performance ratio (32.1RMB/MPa) and the carbon-cost ratio (0.76kg/RMB) are reduced by 86 %, 56 % and 68 % respectively. SSM demonstrated better performance in terms of freeze-thaw resistance, seawater erosion resistance and dry-wet resistance when compared to cement. The dry shrinkage value of SSM solidified soil was reduced by approximately 35 % at 40 days compared to cement solidified soil, due to compensatory shrinkage and a reduction in pores. In contrast to the relatively minor impact of seawater erosion and the moderate effects of the wet-dry cycle, freeze-thaw cycles have been shown to cause the most severe structural damage to the micro-structure of solidified soil. The conduction of durability tests resulted in increased porosity and the most probable aperture. The increase in pores and micro-structure leads to the attenuation of macroscopic mechanical properties of SSM solidified soil. The engineering application verified that with the content of SSM of 50 kg/m, 4.5 % and 3 %, the strength, bearing capacity and bending value of SSM modified soil were 1.9 MPa, 180 kPa and 158, respectively in deep mixing piles, shallow in-situ solidification, and roadbed modified soil field.

The incorporation of PCMs in energy piles holds significant potential for revolutionising thermal management in construction, making them a crucial component in the development of next-generation systems. The existing literature on PCM-integrated energy piles largely consists of isolated case studies and experimental investigations, often focusing on specific aspects without providing a comprehensive synthesis to guide future research or practical applications. To date, no review has been conducted to consolidate and evaluate the existing knowledge on PCMs in energy piles, making this review the first of its kind in this field. Up until now, this gap in research has limited our understanding of how PCM configurations, thermal properties, and integration methods impact the thermal and mechanical performance of these systems. Through thoroughly analysing the current research landscape, this review discovers key trends, methodologies, and insights. The methodology used here involved a systematic search of the existing SCI/SCIE-indexed literature to ensure a structured review. Based on the SLR findings, it is evident that current research on PCMs in energy piles is focused on improving thermal efficiency, heat transfer, and compressive strength. Furthermore, precise adjustments in melting temperature significantly impact efficiency, with PCM integration boosting thermal energy extraction by up to 70 % in some cases, such as heating cycles, and saving up to 30 % in operational costs. PCMs also reduce soil temperature fluctuations, improving structural integrity through minimising axial load forces. However, challenges remain, including reduced mechanical strength due to voids and weak bonding, high costs, and complexities such as micro-encapsulation. We acknowledge that there are gaps in addressing certain key factors, including thermal diffusivity; volume change during phase transitions; thermal response time; compatibility with construction materials; interaction with soil, creep, and fatigue; material compatibility and durability; and the long-term energy savings associated with PCM-GEP systems.

The stress state and density of soil have been considered as the key factors to determine the liquefaction resistance. However, the results of seismic liquefaction case histories, laboratory tests and centrifuge model tests show that the fabric characteristics also influence liquefaction resistance, even more significantly than the contributions of stress state and density. In this study, anisotropic specimens with different consolidation histories were prepared using the 3D Discrete Element Method (DEM) to investigate the influence of fabric characteristics on the mechanical behavior of granular materials and the underlying mechanisms. The simulations revealed that under monotonic shear conditions, horizontally anisotropic specimens exhibited strain hardening and dilatancy characteristics, as well as higher peak strength. Under cyclic shear condition, the normalized liquefaction resistance of the specimens showed a strong linear relationship with the degree of anisotropy, independent of confining pressures and density. Microscopic results indicate that the fabric arrangement aligned with the loading direction leads to the evolution of the mechanical coordination number and average contact force in a manner favorable to resisting loads, which is the underlying mechanism influencing macroscopic mechanical properties. Additionally, the evolution patterns of contact normal magnitude and angle in anisotropic granular materials under cyclic loading conditions were also analyzed. The results of this study provided a new perspective on the macroscopic mechanical properties and the evolution of the microstructure of granular soils under anisotropic conditions.

An integrated constitutive model has been developed for rock-like materials, incorporating confinement-sensitive damage and bi-mechanism plasticity. The model aims to improve the capability of the conventional damage model in depicting the strengthening and brittle-to-ductile transitions that occur under both active and passive confinement conditions. A thermodynamic analysis of energy transformation and dissipation, considering both damage and plasticity, underpins the model's development. The model, rooted in damage-plastic theory, has been divided into two sub-models: (1) Confinement-Sensitive Model: This sub-model addresses the strengthening and ductility enhancements due to active confinement stress. It effectively captures the mechanical responses of rock-like materials under various levels of active confining stresses. (2) Endochronic Dilatancy Model: Based on endochronic theory, a separate dilatancy strain model is proposed, which effectively facilitates the interplay between lateral dilatancy and the growth of passive confining stress. Both sub-models, as well as the integrated model, have undergone validation using experimental data, including uniaxial tests, cyclic loading tests, actively confined tests, and passively confined tests of rock-like materials. These validations confirm the model's accuracy and reliability in predicting the mechanical behavior of rock-like materials under complex loading conditions.

The practice of widening levees to mitigate frequent river flooding is globally prevalent. This paper addresses the pressing issue of sand-filled widened levee failures under the combined effect of heavy rainfall and high riverine water levels, as commonly observed in practice. The primary objective is to illuminate the triggering mechanism and characteristics of such levee failures using the well-designed physical model experiment and Material Point Method (MPM), thus guiding practical implementations. Experimentally, the macro-instability of the levee, manifested as slope failure within the sand-filled widened section, is primarily triggered by changes in the stress regime near the levee toe and continuous creep deformation. Upon failure initiation, the levee slope experiences a progressive failure mode, starting with local sliding, followed by global sliding, and ultimately transitioning into a flow-like behaviour, which characterises the slide-to-flow failure pattern. The slope failure along the interface between the original and new levees is the result of shear deformation rather than the cause. Parametric studies conducted using the calibrated MPM model reveal a critical threshold for the widening width, beyond which the volume of sliding mass and travel angle exhibit no further variation. Increasing the cohesion of the river sand used for levee widening demonstrates the most pronounced improvement in levee stability in the face of the combined effect of intense rainfall and elevated river levels. The MPM-based evaluation of common slope protection measures demonstrates the superior protective benefits of grouting reinforcement and impervious armour layer protection, providing valuable insights for reinforcement strategies in levee engineering applications.