Silica fume and carbide slag can be used to modify waste mud soil (WMS), which can not only improve the mechanical properties of WMS, but also broaden resource utilization ways of silica fume and carbide slag. For that, in this paper, WMS was modified by adopting 8 % carbide slag and silica fume with different dosages (0, 3 %, 5 %, 7 %, 9 %, and 11 %). Then the small-strain dynamic properties of modified WMS were investigated by using resonance column test, and the microscopic mechanism of modified WMS was analyzed based on Scanning electron microscopy (SEM), Energy dispersive X-ray spectrometer (EDS), Transmission electron microscopy (TEM), X-ray diffraction test (XRD) and Mercury intrusion porosimetry (MIP). It can be found from the resonance column test that the dynamic shear modulus and the damping ratio show an increasing and decreasing trend with the increase of the confining pressure respectively, and both increase with increasing silica fume dosage in the range of 0 to 11 %. A kinetic model applicable to modified WMS was established by introducing the effects of confining pressure and silica fume into the Hardin-Drnevich model. Microscopic testing experiments indicate that there is a reaction between reactive SiO2 in silica fume and Ca(OH)2 in carbide slag, and calcium hydrated silicate (CSH) was generated, which improved the specimen density.

In cold regions, the strength and deformation characteristics of frozen soil change over time, displaying different mechanical properties than those of conventional soils. This often results in issues such as ground settlement and deformation. To analyze the rheological characteristics of frozen soil in cold regions, this study conducted triaxial creep tests under various creep deviatoric stresses and established a corresponding Discrete Element Method (DEM) model to examine the micromechanical properties during the creep process of frozen clay. Additionally, the Burgers creep constitutive model was used to theoretically validate the creep deformation test curves. The research findings indicated that frozen clay primarily exhibited attenuated creep behavior. Under low confining pressure and relatively high creep deviatoric stress, non-attenuated creep was more likely to occur. The theoretical model demonstrated good fitting performance, indicating that the Burgers model could effectively describe and predict the creep deformation characteristics of frozen clay. Through discrete element numerical simulations, it was observed that with the increase in axial displacement, particle displacement mainly occurs at both ends of the specimen. Additionally, with the increase in creep deviatoric stress, the specimen exhibits different deformation characteristics, transitioning from volumetric contraction to expansion. At the same time, the vertical contact force chains gradually increase, the trend of particle sliding becomes more pronounced, and internal damage in the specimen progresses from the ends toward the middle.

This study developed a novel geopolymer (RM-SGP) using industrial solid wastes red mud and slag activated by sodium silicate, aiming to remediate composite heavy metal contaminated soil. The effects of aluminosilicate component dosage, alkali equivalent, and heavy metal concentration on the unconfined compressive strength (UCS), toxicity leaching characteristics, resistivity, pH, and electrical conductivity (EC) of RM-SGP solidified composite heavy metal contaminated soil were systematically investigated. Additionally, the chemical composition and microstructural characteristics of solidified soil were analyzed using XRD, FTIR, SEM, and NMR tests to elucidate the solidification mechanisms. The results demonstrated that RM-SGP exhibited excellent solidification efficacy for composite heavy metal contaminated soil. Optimal performance occurred at 15 % aluminosilicate component dosage and 16 % alkali equivalent, achieving UCS >350 kPa and compliant heavy metal leaching (excluding Cd in high-concentration groups). Acid/alkaline leaching tests revealed distinct metal behaviors: Cu/Cd decreased progressively, while Pb initially declined then rebounded. Microstructural analysis indicated that RM-SGP generated abundant hydration products (e.g., C-A-S-H, N-A-S-H gels), which acted as cementitious substances wrapping soil particles and filling and connecting pores, thereby increasing the soil's compactness and improving the solidification effect. Furthermore, heavy metal ions were solidified through adsorption, encapsulation, precipitation, ion exchange, and covalent bond et al., transforming their active states into less bioavailable forms, proving novel insights into the remediation of composite heavy metal contaminated soils and the resource utilization of industrial solid wastes.

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.

Water-induced disintegration is a critical issue in soil stabilization. In this study, soda residue (SR) and fly ash (FA) were mixed to improve the properties of high liquid limit clay (HLC), forming soda residue-fly ash stabilized clay (SRFSC), with cement and/or lime for further stabilization. The mix proportions of the SRFSC were optimized by the orthogonal method, using the compaction, unconfined compressive strength, shear, and disintegration tests. Meanwhile, microscopic tests were performed to reveal the possible mechanical mechanisms. The results showed that the SR and FA content are the primary determinants influencing the mechanical properties of SRFSC. When the base proportion is 70 % SR + 20 % FA + 10 % HLC, the strength is highest (2.45 MPa). At this proportion, the specimen with no cementitious material exhibits the best water disintegration resistance (WDR), reaching 107 min. Adding cement and lime can significantly enhance the WDR of the SRFSC, from complete disintegration at 0.28 min to remaining intact after soaking for 28 days. During field application, the cementitious materials content can be adjusted according to the actual conditions. The superior mechanical properties and WDR of SRFSC are mainly due to the good gradation and dense microstructure. The soda residue can provide abundant Ca2+ to enhance both the mechanical properties and WDR of SRFSC.

To study the failure mechanism of high ductile coagulation (HDC) under sulfate attack in cold saline soil area, cement-based cementing material (cement: fly ash: sand: water reducing agent: water = 1:1:0.72:0.03:0.58) and 2 % polyvinyl alcohol fiber (PVA) were used to prepare HDC sample, to increase the density and ductility of concrete. a 540-day sulfate-long-term immersion test was performed on HDC specimens under two low-temperature curing environments and different sulfate solution concentrations (5 %, 10 %). Using a combination of macro and microscopic methods, according to the principle of energy dissipation, To study the relationship between the evolution of energy (total damage energy U, dissipated energy Uds, elastic strain energy Ues) and the deterioration of strength and the change of pore structure during the compression process of HDC. According to the characteristics of stress-strain curves during HDC compression, the damage evolution characteristics of characteristic stress points during HDC compression are summarized, establish energy storage indicators Kel to evaluate the degree of internal damage of HDC. The results show that during the compression damage process of HDC after long-term soaking in sulfate solution under low temperature environment, Uds and Ues of HDC at characteristic stress points both increase first and then decrease, Kel are reduced first and then increased. The development trend of elastic strain energy and dissipative energy of HDC in 10 % sulfate solution is more drastic than that in 5 % sulfate solution. Compared with the other three groups, the D group energy storage level rises and falls more violently, and the HDC has a smaller ability to resist damage under this condition. Through the study of the correlation between macro and micro changes of HDC in cold saline soil areas and energy evolution, to provide a reference for the stable operation of highly ductile concrete in cold saline soil areas.

Red mud is a kind of solid waste, which can be used as engineering roadbed filler after proper treatment. Due to the special physical and chemical properties of red mud, such as high liquid limit and high plasticity index, it may affect the stability of soil. Therefore, red mud can be improved by adding traditional inorganic binders such as lime and fly ash to improve its road performance as roadbed filler. Red mud-based modified silty sand subgrade filler will be affected by dry-wet alternation caused by various factors in practical application, thus affecting the durability of the material. In order to study the strength degradation characteristics and microstructure changes of red mud, lime and fly ash modified silty sand subgrade filler after dry-wet cycle, the samples of different curing ages were subjected to 0 similar to 10 dry-wet cycles, and their compressive strength, microstructure and environmental control indexes were tested and analyzed. The results show that the sample cured for 90 days has the strongest toughness and the best ability to resist dry and wet deformation. With the increase of the number of dry-wet cycles, the mass loss rate of the sample is in the range of 6 similar to 7 %, and the unconfined compressive properties and tensile properties decrease first and then increase. There are continuous hydration reactions and pozzolanic reactions in the soil, but the degree of physical damage in the early stage of the dry-wet cycle is large, and the later cementitious products have a certain offsetting effect on the structural damage. The internal cracks of the sample without dry-wet cycle are less and the structure is dense. After the dry-wet cycle, the microstructure of the sample changed greatly, and the cracks increased and showed different forms. Through SEM image analysis, it was found that the pore structure of the sample changed during the dry-wet cycle, which corresponded to the change law of mechanical properties. After wetting-drying cycles, the leaching concentration of heavy metals in the modified soil increased slightly, but the overall concentration value was low, which was not a toxic substance and could be used as a roadbed material. The study reveals the influence of dry-wet cycle on the strength characteristics and microstructure of red mud, lime and fly ash synergistically improved silty sand, which provides a technical reference for the engineering application of red mud-based materials.

The infiltration and degradation of domestic contaminants have a substantial influence on the mechanical properties of soil. Sucrose is one of the oligosaccharide contaminants with high content and is prone to degradation in domestic-source contaminants. In this study, a series of tests were conducted to investigate the changes in the mechanical properties of clayey soil during the sucrose degradation process. First, in different concentrations of sucrose-contaminated soil, the organic matter content during the sucrose degradation process was measured to analyze its degradation characteristics. During the degradation process, the unconfined compressive strength and compression coefficient of the soil were measured to analyze the changes in its mechanical properties. Finally, the changes in the permeability coefficient and microstructure of the soil were analyzed in depth. The findings indicated that the degradation of sucrose and the associated alterations in the mechanical properties of contaminated soil were concentration-dependent. The effect mechanism involved the formation of organic-clay flocs during the early stages of degradation and the alkaline oxides' dissolution in the later stages. These findings contribute to a deeper understanding of the impact of domestic-source pollution on soil and provide references for the reinforcement of contaminated soil.

Lignin can significantly enhance the mechanical properties of loess, showing promising application prospects. For many geotechnical conditions, such as subgrade, fatigue caused by traffic vibration and softening due to rain infiltration are the main damage factors. However, the dynamic response of lignin-modified loess under combined water-load action remains unclear. To address this, studies on the dynamic characteristics and microscopic enhanced mechanisms of lignin-modified loess under combined water-load action were conducted by considering the effects of traffic vibration, water content, confining pressure, and compactness. The dynamic triaxial test results showed that the optimal lignin content is 1.5 %, consistent with the results based on the static test. The dynamic strength and maximum dynamic shear modulus increased by 60.05 %, and 12.39 %, respectively. The results indicate that lignin can effectively enhance the loess's resistance to combined water-load erosion. Additionally, as the amplitude increases, the deterioration rate of dynamic properties of the modified loess under combined water-load action significantly slows down. Furthermore, sensitivity analysis based on variance indicates that water and lignin content have the most significant effect on dynamic properties, followed by compactness and confining pressure. An empirical mechanical model for dynamic shear modulus and damping ratio under multi-factor influence was also established. Finally, combined with microscopic test analysis, the filling and bridging of lignin can effectively reduce the promoting infiltration and promoting cracking effects caused by water-load combined action, thereby enhancing its dynamic characteristics. The research results can provide a theoretical basis for road design and maintenance in loess regions.

This study developed all-solid-waste-based curing agents using industrial solid wastes-ground granulated blastfurnace slag (GGBS), carbide slag (CS), and sulfate solid wastes (electrolytic manganese residue (EMR), desulfurized-gypsum (DG), and phosphogypsum (PG))-to stabilize engineering sediment waste (ESW). Based on the simplex centroid design, three ternary curing agents (GGBS-EMR-CS (GEC), GGBS-DG-CS (GDC), and GGBSPG-CS (GPC)) were prepared. The optimal ratios for GEC, GDC, and GPC are 60:12:28, 70:27:3, and 70:21:9, respectively. Compared to ordinary Portland cement (OPC), the unconfined compressive strength (UCS) of ESW stabilized with these curing agents increased by 78 %, 178 %, and 98 %, respectively. Sulfate components synergistically activates GGBS and CS, promoting needle-like ettringite (AFt) formation, which fills pores and enhances strength. Meanwhile, COQ emissions and costs were reduced up to 99 % and 73 %, respectively. This study developed all-solid-waste-based curing agents with excellent mechanical performance, low costs, and near net-zero emissions, which provided a sustainable solution for ESW stabilization.