Search Results (712)

Seasonal freeze–thaw cycling progressively rearranges pores and propagates microcracks in silty clay, reducing the reliability of cold-region earthworks. This study evaluated a bio–polymer stabilization strategy combining microbially induced carbonate precipitation (MICP) with anionic polyacrylamide (APAM) to improve mechanical performance and freeze–thaw durability. Six groups were prepared at identical moisture and compaction conditions: water, APAM, and four MICP–APAM groups with bacterial optical densities (OD600) of 0.8, 1.0, 1.2, and 1.4. Unconfined compressive strength, unconsolidated-undrained triaxial compression, ultrasonic pulse velocity, and SEM, TG/DTG, XRD, and FTIR analyses were conducted before and after freeze–thaw cycling. The M1.0-APAM group showed the best overall performance, with UCS values of 1.35 MPa before cycling and 0.89 MPa after nine cycles, together with high shear resistance and ultrasonic velocity. Lower bacterial concentration provided insufficient cementation, whereas higher concentrations promoted non-uniform carbonate deposition, pore heterogeneity, and local stress concentration. Microstructural evidence indicated that OD600 ≈ 1.0 produced a relatively homogeneous network of fine carbonate clusters and polymer-associated films, with calcite formation supported by TG/DTG and XRD. The results show that MICP–APAM treatment enhances silty clay primarily through coordinated mineralization uniformity, pore refinement, and polymer bridging, providing a sustainable stabilization option for seasonally frozen soils. Full article

Freezing stress is one of the major abiotic factors limiting plant growth and productivity. This study evaluates the effects of diatomite (DTM) as a natural silicon-rich amendment on growth performance, physiological responses, and cold stress tolerance in barley (Hordeum vulgare L.). Seed priming and substrate application of DTM at different concentrations (5–20%) were used to assess morphological, biochemical, and ultrastructural changes under normal and low-temperature conditions. Results showed that DTM significantly enhanced root growth and biomass accumulation, with the most pronounced effect at 10% concentration. Treated plants exhibited improved survival under freezing stress, along with better preservation of leaf cellular structure and photosynthetic pigments. Biochemical analyses revealed reduced proline accumulation and decreased activity of key antioxidant enzymes, indicating alleviation of oxidative stress and improved redox balance. Electron microscopy confirmed the integration of diatomite particles into seed and tissue structures, providing physical reinforcement and thermal protection. Overall, diatomite acts as a multifunctional, environmentally safe soil amendment that enhances plant growth and improves tolerance to cold stress through combined physical and physiological mechanisms. Full article

Freeze–thaw cycles cause mechanical deterioration and instability of slope rock masses in open-pit coal mines located in the cold regions of Northwest China. In this study, the research object is fine-grained sandstone from the Yan’an Formation in the Tarangole mining area of the Ordos Basin. Here, indoor freeze–thaw cycling, uniaxial compression, and triaxial compression tests were conducted to systematically analyze the deformation behavior, strength evolution, and failure modes of the sandstone under varying numbers of freeze–thaw cycles, freezing temperatures, and confining pressures, thereby revealing its freeze–thaw damage mechanism. The results show that the number of freeze–thaw cycles is the dominant factor affecting the elastic modulus. Freezing temperatures (especially between −5 °C and −15 °C) and the number of freeze–thaw cycles (particularly the first 10 cycles) significantly reduce peak strength. In addition, confining pressure can significantly enhance the resistance to deformation (under 15 freeze–thaw cycles, the elastic modulus increases by 181.8% as confining pressure rises from 0 to 2 MPa). Within the low confining pressure range (0–1.5 MPa), peak strain decreases monotonically with increasing confining pressure and is independent of the number of freeze–thaw cycles. Finally, the increase in the number of freeze–thaw cycles and the decrease in temperature jointly promote crack development, and the failure mode shifts from pure shear to a shear-tension composite mode. The underlying cause lies in the evolution of interparticle cementation within the soil skeleton and in the associated pore–crack structure. In addition, based on fracture damage mechanics and the modified Weibull distribution, a damage evolution equation and a constitutive model for sandstone considering freeze–thaw cycles and temperature effects were established and validated. Therefore, the research findings can provide a theoretical basis for slope support, freeze–thaw disaster prevention and mitigation, and stability assessment in the Tarangole mining area and other cold regions. Full article

In the seasonally frozen area, slopes are exposed to freeze–thaw cycles; thus, water and heat are moved, and the foundation for the transportation infrastructure in cold regions may be weakened. Based on the relatively strong water-recharge effect and considerable fluctuations in shallow soil moisture during the spring thaw along the Naba section of the G218 Highway in Xinjiang, China, a coupled hydro-thermal model for frozen soil that considers snowmelt infiltration and rainfall recharge was developed, and it was numerically implemented in COMSOL. A one-dimensional unidirectional freezing test of a soil column was used to validate the model, and the relative errors of the simulated temperature and moisture fields were 3.8% and 4.3%, respectively; both are within the accuracy requirements for engineering-scale analysis. Then, a model was used to determine how the temperature, volumetric ice content and volumetric water content of a representative slope in the Naba section changed during a freeze–thaw cycle. Based on the above results, the annual temperature range at the surface of the topsoil on the slope is 37.61 °C, and this thermal effect extends to a depth of 0–3 m. In the spring thaw, the volumetric water content of the surface layer increased from 8.45% in February to 19.34% in May, and further to 20.65% in July; therefore, it can be inferred that the shallow soil is still being replenished by snowmelt and rain. Freezing-thaw phase change, freezing-front migration and external water infiltration work together to control hydro-thermal transport in the slope; thus, a redistribution and local accumulation of liquid water occur below the residual frozen layer and under the shallow surface. The above results can serve as a reference for drainage design and as a means to prevent or control freeze–thaw damage to the slope of a highway in Xinjiang’s seasonally frozen area during the spring thaw. Full article

To reveal the electromagnetic response characteristics and hydro-thermal evolution mechanism of frozen soil under microwave irradiation, we used remolded frozen soil prepared from undisturbed parent soil collected in Hegang, China, as the research object. We conducted dielectric parameter tests across the 715–1150 MHz and 2250–2650 MHz frequency bands and 1.5 kW microwave heating tests on specimens with three gravimetric water contents (15%, 20%, and 25%) paired with a coupled numerical simulation of electromagnetic field-heat transfer-moisture migration. The results show that water content is the dominant factor controlling the dielectric response of frozen soil. The dielectric loss and water content sensitivity of frozen soil in the low-frequency band (dominated by unfrozen water) are significantly higher than those in the high-frequency band (dominated by ice phase and soil matrix). Microwave-induced temperature rise exhibits a three-stage characteristic, as follows: slow temperature rise, isothermal plateau at the freezing point, and rapid temperature rise. Specimens with a lower initial water content show a higher temperature rise efficiency in the late heating stage, with a maximum rate of 1.112 °C·s⁻¹ for the 15% water content specimen. Mass loss is negatively correlated with initial water content, with a maximum value of 1.8 g after 120 s of irradiation. In addition, the non-uniformity of the electromagnetic field results in a temperature field pattern characterized by a high-temperature core at the specimen center and lower temperatures at the edges. This study provides fundamental theoretical support and technical guidance for the application of microwave thawing technology in geotechnical engineering, particularly for frozen soil foundation treatment in cold regions. Full article

The scarcity of natural aggregates and the accumulation of oil sludge in desert regions pose critical challenges for highway construction. Although aeolian sand and oil sludge pyrolysis residue have been studied individually as construction materials, their combined use in foamed lightweight soil remains unexplored. This study addresses this gap by developing a novel foamed lightweight soil termed SOFS, which is created through the synergistic modification of aeolian sand and oil sludge pyrolysis residue. A six-factor, five-level orthogonal array (L25) was employed to systematically investigate the effects of residue content, sand content, foam-to-slurry ratio, foaming agent dilution, water-to-solid ratio, and mixing time. The evaluated properties included physical properties (fluidity and wet density), mechanical properties (compressive, splitting tensile, and flexural strength), and durability (wet–dry and freeze–thaw resistance). Scanning electron microscopy was used to examine the microstructural mechanisms. Variance and range analysis identified the optimal mixture, designated H14, which achieved 28-day compressive, splitting tensile, and flexural strengths of 3.75 MPa, 2.21 MPa, and 0.9 MPa, respectively, thereby meeting desert roadbed requirements. Compared with conventional materials, H14 exhibited superior durability, with strength losses of only 16.3% in compressive strength and 19.1% in splitting tensile strength after 25 cycles. Microstructural analysis revealed a dense C-S-H gel network encapsulating the solid waste particles, with nanoscale Al- and Cl-rich crystalline phases observed at interfacial pores—a phenomenon that has rarely been documented in previous studies. These findings provide a theoretical and technical foundation for solid waste valorization and the development of sustainable desert infrastructure. Full article

This study presents a comprehensive analysis of a landslide that occurred in February 2024 in the Tau-Samal district of Almaty, Kazakhstan. Characterized by rapid onset and anthropogenic influence, this event resulted from a complex interaction of environmental and anthropogenic factors. Specifically, the landslide was triggered by seasonal temperature fluctuations leading to multiple freeze–thaw cycles, localized microseismicity (magnitude 3.5 on 4 February 2024), and a major water main break resulting in localized flooding of loess soils. The study utilizes an integrated landslide susceptibility index (LSI) model, which combines the analytic hierarchy process (AHP) for factor weighting. Validation was conducted by comparing the spatial distribution of high-susceptibility zones derived from the LSI model with the actual location of the landslide. Geotechnical studies highlight the susceptibility of Almaty loess, focusing on parameters such as cohesion, internal friction angle, and liquefaction potential. The findings highlight the need for climate-adapted urban policies and improved geotechnical monitoring in high-risk loess areas. This study contributes to a regional understanding of Tien Shan geohazards by placing the Tau-Samal event within the broader context of seismically and hydrologically driven slope processes. Full article

Dredging projects associated with China’s expanding maritime transportation and waterway regulation produce substantial volumes of dredged soil each year. This dredged soil, characterized by poor engineering properties, cannot be directly used for filling projects and requires improvement. On the other hand, the use of solid waste curing agents to replace traditional curing agents for semi-curing improved dredged soil can achieve the goal of treating waste with waste. This study employs a CGF curing agent composed of calcium carbide slag, blast furnace slag, and fly ash for the semi-curing improvement of dredged soil. The impact of the curing agent content on the compaction properties of semi-cured improved dredged soil is investigated. Additionally, through freeze–thaw cycle tests and microscopic experiments, the influence of the number of freeze–thaw cycles on the strength of semi-cured improved dredged soil and its microscopic mechanism are examined. The results indicate that as the curing agent content increases, the maximum dry density of the CGF semi-cured improved dredged soil decreases, while the optimal moisture content increases. Under freeze–thaw cycles, both the mass and unconfined compressive strength of the CGF semi-cured improved dredged soil decrease with an increasing number of cycles. Microscopic test results show that alkali-activated products (C-S-H, C-A-S-H, C-A-H) cement soil particles, fill soil pores, and enhance the internal stability of the soil. However, as freeze–thaw cycles progress, the structure of the CGF semi-cured improved dredged soil is gradually damaged. The enlargement of pores and the formation of penetrating cracks and voids lead to a reduction in strength. Increasing the curing agent content can effectively improve the frost resistance of the CGF semi-cured improved dredged soil. Full article

Forest soils serve as critical terrestrial carbon sinks. While broad hydrothermal controls on soil respiration (R_s) are established, uncertainties persist regarding high-frequency temporal dynamics and moisture-dependent variations in temperature sensitivity (Q₁₀). Specifically, conventional reliance on discrete, clear-day sampling obscures how precipitation disrupts diurnal patterns. To address this, we continuously monitored R_s and environmental factors in two Northeast Chinese mixed forests (Korean pine, Pinus koraiensis (KP), and Dahurian larch, Larix gmelinii (DL)) to quantify weather-driven daily dynamics and carbon fluxes. Precipitation primarily drove daily variability, but more importantly, it reshaped day–night asymmetry. Under clear-day conditions, R_s exhibited a consistent daytime-dominant pattern, with daytime fluxes being significantly higher than nighttime fluxes (p < 0.05). However, precipitation events fundamentally neutralized this asymmetry, resulting in no significant day–night differences across most phenological stages. Annual R_s effluxes (759 and 965 g C m⁻² yr⁻¹ for KP and DL, respectively) lacked significant inter-stand or temporal variations. Seasonal emissions peaked unimodally in July, with the non-growing season contributing merely 5%–8%. Notably, spring freeze–thaw R_s in the KP stand surged interannually by 143%. While R_s correlated positively with temperature (p < 0.001), Q₁₀ was co-regulated by forest stand and moisture. Under moderate moisture, the KP stand’s Q₁₀ (2.72) was significantly lower than the DL stand’s (3.81); however, this divergence neutralized under low moisture. Consequently, soil moisture acts as both a direct R_s driver and a fundamental regulator of its temperature sensitivity. These empirical findings provide critical data to calibrate forest carbon models, improving predictions of soil carbon feedbacks under future climate scenarios. Full article

This study investigates the mechanical behavior and durability performance of kaolin clay stabilized using a hybrid system composed of Xanthan Gum biopolymer, polypropylene fibers, and Trivoltherm waste fibers. Experimental studies were designed according to the Taguchi L16 orthogonal array to evaluate the effects of different additive combinations. Unconfined compressive strength tests were performed after curing periods of 7, 28, and 90 days, while durability behavior was assessed through 5 and 10 freeze–thaw cycles. In addition, scanning electron microscopy analyses were conducted to investigate the microstructural characteristics of the stabilized soils. The results indicated that strength increased significantly with curing time, reaching a maximum value of 1186 kPa after 90 days. Statistical analyses showed that Xanthan Gum was the dominant parameter affecting strength development, contributing approximately 57–63% to the unconfined compressive strength behavior. Fiber additives also improved ductility, crack resistance, and freeze–thaw durability through reinforcement and crack-bridging mechanisms. The best-performing mixtures exhibited markedly lower strength losses under freeze–thaw conditions compared with untreated soil specimens. Analysis of variance results confirmed that the investigated parameters were statistically significant (p < 0.05), and the developed models showed high prediction accuracy (R² > 85%). Overall, the findings demonstrate that the synergistic interaction between the biopolymer matrix and fiber reinforcement system provides an effective and sustainable hybrid stabilization approach for improving the engineering performance of clay soils. Full article

The Ili River Valley is a typical seasonally frozen region in which slope instability frequently occurs during the warm frozen-soil stage, generally at temperatures ranging from approximately −1.5 to 0 °C. In this context, changes in unfrozen water content play an important role in controlling the pore structure and mechanical behavior of warm frozen soil, yet the links among these factors remain insufficiently understood. This study investigates warm frozen soil from the Ili River Valley, with particular emphasis on the role of unfrozen water content in regulating pore-structure characteristics and mechanical response under low-temperature conditions. Low-field nuclear magnetic resonance (NMR), low-temperature triaxial shear tests, scanning electron microscopy (SEM), and quantitative image analysis were employed to examine the relationships between unfrozen water content, pore structure, and macroscopic mechanical properties under different temperatures, initial water contents, and confining pressures. The results show that unfrozen water content decreases markedly with decreasing temperature, especially within the range of −1.5 to −5 °C, and increases with increasing initial water content. These changes are accompanied by significant variations in porosity, pore abundance, and pore fractal dimension, reflecting freezing-induced reorganization of the pore system. Lower temperatures and higher initial water contents promote ice-crystal growth and the formation of larger ice-cemented aggregates, thereby modifying the pore framework. Meanwhile, peak strength and cohesion increase with decreasing temperature and increasing initial water content, whereas the internal friction angle shows a decreasing trend. In addition, porosity, pore abundance, and pore fractal dimension are closely correlated with peak strength and cohesion. The results indicate that unfrozen water content governs the freezing-induced reorganization of pore structure, which in turn controls the strength evolution of warm frozen soil. These findings improve understanding of the role of unfrozen water in low-temperature soil structure and strength evolution and provide a basis for evaluating slope instability in the Ili River Valley. Full article

The pursuit of sustainable winter road maintenance has intensified the need for deicers that balance functional effectiveness, economic viability, and minimal environmental impact. However, the absence of a systematic, multi-dimensional evaluation framework has hindered informed product selection and green procurement. This study develops and validates the Comprehensive Deicer Multi-criteria Evaluation System (CDMES)—a structured assessment framework that integrates economic, functional, environmental, and infrastructural sustainability dimensions. The evaluation index system was constructed for deicers, consisting of 18 indicators including preparation cost, engineering maintenance cost, operability of agent preparation, application difficulty, asphalt binder adhesion loss, minimum application concentration, proportion of active ingredients, effective time, ambient temperature, freezing point, solid dissolution rate, relative snow/ice-melting capacity, seed damage rate, chlorophyll attenuation, soil pH, aqueous solution pH, steel–carbon corrosion rate, and pavement friction attenuation rate. Subsequently, the analytic hierarchy process (AHP) was employed to determine the weight of each indicator, and evaluation criteria were established in accordance with relevant standards and literature. Finally, this weight determination method, combined with the simple additive weighting (SAW) method for index aggregation, forms a quantitative evaluation model. These elements together constitute a comprehensive deicer evaluation system, designated as the Comprehensive Deicer Multi-criteria Evaluation System (CDMES). Validation using three representative deicers—sodium chloride, a composite chloride-based formulation, and an organic acetate-based product—demonstrated that the CDMES can effectively discriminate product performance across multiple sustainability dimensions and identify critical weaknesses that may be obscured by purely compensatory scoring. The framework offers a transparent and reproducible decision-support tool for winter maintenance managers seeking to align deicer selection with sustainability objectives. Full article

Soils in cold seasonally frozen regions undergo repeated freeze–thaw (F–T) cycles, during which soil moisture content, pore structure, and permeability can change substantially. Previous studies have mainly focused on the mechanical behavior of such soils, whereas few have clarified how moisture content fluctuation regulates pore-structure evolution and permeability response during F–T cycling. In this study, black soil specimens were prepared with initial moisture contents of 15%, 20%, 25%, and 30% on a dry-weight basis and were denoted as 15%-MC, 20%-MC, 25%-MC, and 30%-MC, respectively. The specimens were subjected to 0, 1, 3, 6, 9, and 12 F–T cycles. Mercury intrusion porosimetry, scanning electron microscopy image analysis, and variable-head permeability tests were used to characterize pore-structure parameters and hydraulic responses. The results showed that porosity and mean pore diameter generally increased with increasing F–T cycle number, and the magnitude of these increases depended on the initial moisture content. The 15%-MC group exhibited limited pore expansion, mainly characterized by a transition from micropores to small pores, whereas the 25%-MC and 30%-MC groups developed more mesopores and macropores. In the 30%-MC group, porosity reached its maximum after 9 F–T cycles and then decreased slightly after 12 cycles, indicating particle rearrangement or partial filling of larger pores. The permeability coefficient and cumulative infiltration also increased with increasing F–T cycle number, with more pronounced increases observed in the high-moisture groups. Tukey’s post hoc test showed that the permeability coefficients in the later F–T stages were higher than those in the early stages, particularly in the 25%-MC and 30%-MC groups. Correlation analysis and principal component regression indicated that the permeability coefficient and cumulative infiltration were positively correlated with porosity, mean pore diameter, mesopores, and macropores, but negatively correlated with micropores. Overall, the initial moisture content regulated pore-size redistribution and seepage-channel development, thereby shaping the hydraulic response of black soil under repeated F–T cycling. Full article

Freeze–thaw cycles are the main cause of subgrade damage in cold regions. To investigate how straw fibers affect the road performance of reinforced black soil in these areas, this study conducted unconfined compressive strength (UCS), California bearing ratio (CBR), and resilient modulus (RM) tests, supplemented by CT scanning. The novelty lies in comparing coarse and fine straw fibers and establishing a freeze–thaw damage prediction model. It analyzed the effects of straw fiber types (coarse and fine) and contents (0, 0.5%, 1.0%, 1.5%, 2.0%, 2.5%) on the soil’s mechanical properties and reinforcement mechanisms. Results showed that straw fibers enhance soil mechanics by distributing stress, limiting soil particle movement, inhibiting crack growth, and reducing porosity. Fiber content impacts the mechanical properties of reinforced soil more significantly than fiber type. The optimal fiber content for both coarse and fine straw fibers is 1%. At this content, the UCS of coarse fiber-reinforced soil (CFS) reached 1.11 MPa, a 32.14% increase compared to the reference group (B-0), and the RM reached 207.39 MPa, a 63.70% increase compared to B-0. Meanwhile, the UCS of fine fiber-reinforced soil (FFS) reached 1.01 MPa, a 20.24% increase, and the RM reached 150.33 MPa, an 18.66% increase. Freeze–thaw cycles degrade mechanical properties by weakening the bond between soil and straw fibers. As the number of freeze–thaw cycles increases, both the UCS loss rate and RM loss rate rise. FFS exhibits superior freeze–thaw resistance compared to CFS, due to its lower porosity and fewer cracks. The developed freeze–thaw damage evolution equation shows a strong fit (R² > 0.85) and applies to straw fiber-reinforced black soil under the conditions of this study. This research provides a theoretical basis for designing eco-friendly straw fiber-reinforced subgrades in cold regions. Full article

To elucidate the mechanisms by which the rhizosphere microbial community influences cold tolerance in maize, this study employed the metagenomic technology to systematically analyze the community composition, functional characteristics, and their association with host cold tolerance in the rhizosphere of maize genotypes with different cold tolerance (cold-tolerant material B144 and cold-sensitive material Q319, among others) (n = 3 biological replicates per genotype). The results revealed that the rhizosphere microbial community of the cold-tolerant genotype B144 exhibited higher species diversity and more complex genomic features. LEfSe analysis indicated that the rhizosphere soil microbiota of B144 was significantly enriched in two major phyla, Firmicutes and Actinobacteria, as well as microbial taxa with stress tolerance potential, such as the Bacillus and Streptomyces. Further functional analysis revealed that the microbial community was specifically enriched in metabolic pathways related to glycan biosynthesis and metabolism, as well as coenzyme and vitamin metabolism. We hypothesize that the physiological stability of maize under low temperatures can be enhanced through mechanisms such as the synthesis of extracellular polysaccharides to reduce the freezing point and the provision of vitamins and antioxidant substances. In contrast, the rhizosphere microorganisms of the cold-sensitive material Q319 were more enriched in basic metabolic functions. The present study elucidates the pivotal mechanisms by which rhizosphere microorganisms facilitate maize resistance to low-temperature stress from a functional perspective. This provides theoretical support and new strategies for enhancing crop stress resistance by regulating the rhizosphere microbiome. Full article