The large-scale generation and improper disposal of Iron Ore Tailings (IOT) pose significant environmental and geotechnical challenges, necessitating sustainable reuse strategies. This study investigates the geopolymer-based stabilization of IOT using alkali-activated binders composed of Ground Granulated Blast Furnace Slag (GGBS) and Fly Ash (FA). The IOT content was fixed at 90%, while FA and GGBS (10% total) were varied in three proportions: 90:2.5:7.5, 90:5:5, and 90:7.5:2.5 (IOT: FA: GGBS). Sodium hydroxide (NaOH) solutions of 2.5 M and 5 M were combined with sodium silicate (Na2SiO3) at NaOH: Na2SiO3 ratios of 1:1 and 2:1. Mechanical testing revealed that the 90:2.5:7.5 mix activated with 5 M NaOH at a 1:1 ratio achieved the highest 28-day strengths of 11.14 MPa (UCS) and 0.93 MPa (STS). Statistical analysis (ANOVA) confirmed curing duration and NaOH molarity as the dominant parameters governing strength development. Microstructural investigations (XRD, SEM, EDS) demonstrated that enhanced performance is associated with the formation of hybrid C-A-S-H and N-A-S-H gel networks, resulting in matrix densification and improved interparticle bonding. Toxicity Characteristic Leaching Procedure (TCLP) results verified reduced heavy metal leachability within regulatory limits. The findings establish that geopolymerization enables effective transformation of IOT into a high-performance, cement-free geomaterial, offering a sustainable pathway for large-scale tailings valorization and construction applications.

Accurate characterization of soil thermal conductivity is important for understanding heat transfer in geotechnical and environmental applications. This study investigates the effect of biochar amendments on the thermal conductivity of soils under controlled laboratory conditions and develops a machine learning-based predictive framework to improve estimation accuracy. Experiments were conducted on kaolin and silty sand mixed with 10

Accurate evaluation of undrained shear strength (Su) is crucial for the safe design of foundations and slopes in marine alluvial clays, including those commonly found in Bangkok. In this study, we assembled an automated machine learning (AutoML) workflow using open-source Python libraries to explore suitable predictive models for Su based on 152 undisturbed clay samples. The input variables considered include depth, moisture content, liquid limit, plastic limit, vane shear strength (PP), and total unit weight. Across the models evaluated, ridge regression offered a stable balance between accuracy and computational efficiency, with a mean absolute error of 0.550 t/m2, a root mean square error of 0.710 t/m2,, and an R² of 0.809, while requiring less than 0.05s of training time. The AutoML process facilitated a more transparent comparison of candidate algorithms, providing insight into variable relevance. Specifically, PP, depth, and unit weight emerged as the most influential predictors. Traditional index properties showed comparatively lower contributions. Five-fold cross-validation suggested that the selected model maintained consistent performance (mean R² = 0.810; standard deviation = 0.025). These results suggest that a streamlined AutoML workflow can aid in identifying reliable and easy-to-interpret models for Su estimation in Bangkok clays. Such an approach may complement laboratory testing and help reduce some of the uncertainty associated with empirical correlations, especially in preliminary design stages.

Existing studies have demonstrated that cracking is a fundamental cause of soil slope instability, while uneven water evaporation is the primary factor contributing to crack development. Appropriate moisture management measures can effectively reduce cracking risks. Therefore, investigating the mechanisms by which drip irrigation technology and vegetation influence expansive soil slopes holds significant theoretical and engineering importance. This study established four slope models: Biochar-Amended Expansive Soil Slope (BAES), Drip-Irrigated Biochar-Amended Expansive Soil Slope (DI-BAES), Vegetated Biochar-Amended Expansive Soil Slope (V-BAES), and Drip-Irrigated Vegetated Biochar-Amended Expansive Soil Slope (DI-V-BAES). An outdoor slope model box test was conducted over an entire summer season (100 days) to examine the effects of drip irrigation and vegetation on shallow stability of biochar-amended expansive soil slopes. Results show that drip irrigation and vegetation significantly impact the shallow stability. The drip irrigation system effectively maintains slope soil moisture through continuous water supply, thereby reducing soil drying and crack formation. Vegetation substantially improves soil shear strength, reduces soil scouring, and enhances erosion resistance through root reinforcement and canopy coverage. The combination of both measures further optimizes slope stability, with the DI-V-BAES model demonstrating the best performance in maintaining temperature stability, moisture content stability, reducing fissure rates, and improving scour resistance. This approach significantly enhances the overall stability and erosion resistance of expansive soil slopes, representing an effective measure for long-term slope stability. Additionally, drip irrigation promotes vegetation growth, increasing root density and slope-holding capacity, while vegetation improves soil cohesion and internal friction angle through root system development. In conclusion, the synergistic management model of drip irrigation and vegetation provides theoretical foundations and practical guidance for expansive soil slope protection.

Abstract Soil reinforcement is a potential solution to mitigate wind‐induced sand erosion. Previously, microbiologically induced calcite precipitation (MICP) has been used to control sand erosion and enhance the strength of soil particles. However, it has limitations. The present study explores the effectiveness of an alternative biologically inspired method, enzyme‐induced carbonate precipitation (EICP), in enhancing the stability and strength of aeolian sand. The novelty of this study lies in the identification of an optimal dosage through a multiscale evaluation of EICP performance, specifically targeting high‐velocity erosion resistance (up to 30 m/s), surface strength uniformity, penetration depth, mechanical reinforcement and the explicit characterization of calcite thermal stability. Plant‐based Jack bean urease was used at varying concentrations with a 1‐M cementation solution. To mitigate wind‐induced sand erosion, surface treatment was performed using the spray method. The treated specimens were subjected to a wind tunnel test, a surface strength test, a calcite test, scanning electron microscopy (SEM) analysis and energy‐dispersive X‐ray spectroscopy (EDX) analysis. To evaluate the strength of soil particles, unconfined compressive strength (UCS) and split tensile strength (STS) samples were treated using the stopped and gravity flow methods and were tested for UCS, STS, ultrasonic pulse velocity (UPV) and calcite formation. Additionally, to assess the thermal behaviour of the formed calcite, thermogravimetric analysis (TGA) was performed. The study demonstrated that the EICP method effectively mitigates erosion up to a wind speed of 30 m/s and achieves optimal soil strength, with a maximum UCS value of 756 kPa and 5% calcite formation. However, practical implementation considerations, including extended treatment duration and long‐term durability under field conditions, require further investigation before large‐scale application.

The frequent occurrence of dry spells, heatwaves, and water scarcity takes a toll on green infrastructure, particularly in arid and semi-arid regions. Water-absorbing polymers (WAPs) have the potential to minimise the effects of water stress on plant growth. It can absorb and store large amounts of water and release it when water is unavailable in the soil matrix. This study conducted experimental and numerical research on a novel water-absorbing polymer derived from waste-generated fly ash, aiming to improve the drought resistance of vegetated soils, with a focus on root water uptake () dynamics. The fundamental goal of this research is (1) to establish the efficacy of WAP-amended soil on grass species under water stress conditions and (2) to estimate the from soil under the effect of . The results demonstrate that the improved water retention behaviour by altering water storage in the soil matrix. The water retention characteristics, such as plant-available water content and wilting time, were improved by more than 2 times and 1.2 times, respectively, compared to the control soil. Furthermore, it is observed that WAP-amended soil has higher from the soil matrix. This study suggests that can be utilised for a variety of applications, including green infrastructure and agricultural practices.

Biochar has been widely incorporated into landfill cover soils to enhance moisture regulation due to its porous structure and strong water retention capacity. Plant fibers, as abundant and renewable materials, also offer potential as soil amendments. However, little research has addressed the coupled effects of biochar-fiber composites on soil hydraulic and mechanical behavior under unsaturated conditions. This study investigates their influence on CO2 permeability (ka), hydraulic conductivity (kw), and shear strength in sandy loam. Laboratory experiments examined the effects of reed straw biochar (5

This study evaluates the thermal regulation performance and energy-saving potential of extensive green roof (GR) systems in a subtropical less-developed region. A yearlong field experiment on a nine-story building in Guangxi, China, compared the thermal dynamics of a GR against a conventional roof (CR). Measurements showed the GR significantly attenuated temperature fluctuations, reducing summer peak roof surface and indoor temperatures by up to 8.6 °C and 5.35 °C, respectively. Results indicated exceptional thermal stability, with the GR damping diurnal surface temperature fluctuations by approximately 50%. Furthermore, validated energy simulations across four building typologies reveal that actualized energy benefits are strictly dictated by operational schedules. A substrate thickness benchmark analysis demonstrates that while continuous-operation facilities (e.g., hospitals) benefit monotonically from thicker substrates, intermittently operated buildings suffer from distinct “thermal lag” and “weekend thermal storage” effects, making lightweight configurations dynamically optimal. Ultimately, a practical four-step decision-making flow is proposed to guide urban planners in screening retrofit priorities. These findings elucidate the dynamic thermal buffering mechanisms, providing actionable guidelines for sustainable urban development in subtropical regions.

Current research suggests that excessive surface moisture loss in expansive soil slopes promotes cracks and may trigger slope instability. Appropriate drip irrigation replenishes near-surface water, minimizing or delaying crack formation. The objective of this study was to clarify the moisture migration mechanisms under a newly designed drip-irrigation scheme, to guide system optimization and water-use efficiency. Three slope-model tests were conducted with systematically varied emitter flow rates. Furthermore, the influence of biochar on moisture migration was further analysed. The test results demonstrate that drip emitter flow rate significantly affects soil moisture migration. Specifically, higher drip emitter flow rate lengthens the response time of volumetric water content at the same sensor location. At the same drip irrigation time, the wetting front migration distance increases with drip emitter flow rate. The horizontal-to-vertical infiltration ratio of the wetting front decreases with drip emitter flow rate. During redistribution, the wetting front displacement shows negative growth in the downslope horizontal direction, with its magnitude increasing as drip emitter flow rate increase, while other directions show positive growth. The drip emitter flow rate should not be excessively high or low; otherwise, it reduces the uniformity of soil moisture movement. This study identified 0.4 L/h as the optimal drip emitter flow rate. At 0.4 L/h, wetting-front migration in all directions decelerates with infiltration time. The profile shape of the wetted body and the slope-surface footprint are approximately elliptical and an elliptical function can therefore estimate wetted volume, thereby providing a theoretical foundation for slope drip-irrigation design.

Rapid urbanization and climate change intensify water stress, threatening urban green infrastructure (UGI). Water-absorbing polymers (WAPs) are a promising solution to enhance soil water retention and plant drought resilience. This review applies the Soil–WAP–Plant–Atmosphere (SWPA) framework as an analytical tool to conduct an in-depth assessment of the mechanisms among soil hydraulic behavior, WAP properties, plant physiological responses and atmospheric factors. This comprehensive analysis reveals previously unrecognized mechanistic gaps and provides a roadmap for interdisciplinary research and development of water-efficient urban green infrastructure strategies. The synthesis examines studies on WAP applications, analyzing soil hydraulic properties, plant growth parameters, and environmental interactions. Emphasis is placed on the integrated soil–WAP–plant–atmosphere framework to evaluate system-scale impacts. WAPs significantly improve soil water-holding capacity and modify the soil–water characteristic curve, enhancing plant water availability. The presence of WAP can promote better root development, stomatal conductance and photosynthetic efficiency under abiotic stress condition in plants. In addition, by maintaining soil moisture availability, WAPs can regulate evapotranspiration (ET) dynamics for better plant growth. However, key uncertainties remain regarding optimal application rates, long-term stability, salinity tolerance, environmental impacts, and large-scale economic feasibility. The findings confirm WAPs' potential to boost drought resilience and water efficiency in UGI. They also highlight the necessity for further interdisciplinary research integrating soil physics, plant biotechnology, and urban climatology. This review offers practical insights for developing sustainable strategies while noting unresolved challenges in environmental impact and scalability.

Iron ore tailings (IOT), a by-product of mining, present significant environmental challenges due to their disposal. Previous studies have explored the use of IOT in construction and geotechnical applications, but limitations such as inadequate strength development and environmental concerns have restricted its widespread adoption. The motivation for this study stems from the need for a sustainable and effective solution to repurpose IOT while addressing these challenges. This study investigated a sustainable approach to utilizing IOT as a backfill material by incorporating fly ash (FA) to enhance its mechanical properties. The mix proportions of FA to IOT were 3

Shallow soil desiccation in expansive soil slopes can induce cracking, triggering slope failure. Previous studies have demonstrated that incorporating 5% corn stover biochar into expansive soil can effectively enhance the soil's water retention capacity and inhibit crack development. To investigate the impact of adding 5% corn stover biochar on the stability of expansive soil slopes under vegetation-covered conditions, this study establishes two groups of expansive soil slope models overlaid with Manila grass, one modified with biochar and the other without. Over 60 days under natural conditions, vegetation growth, shallow soil temperature variations, and moisture content changes were monitored. Results indicate that biochar-amended slopes exhibited a higher leaf area index compared with untreated slopes, demonstrating that biochar promotes plant growth. In addition, biochar application reduced soil temperature and minimised thermal fluctuations, thereby lessening atmospheric weathering effects on shallow soil layers. The volumetric water content in biochar-treated slopes showed more stable behaviour, limiting crack propagation and improving slope stability. These findings highlight biochar's potential as a sustainable solution for stabilising expansive soil slopes by enhancing vegetation performance, regulating soil temperature, and maintaining moisture equilibrium, thus reducing environmental degradation risks.

Plant microbial fuel cell (PMFC) is a promising technology that could be applied in green infrastructures such as green roofs for bioelectricity generation. While previous research has explored the influence of soil water characteristics on PMFCs in laboratory settings, this investigation extends to understanding natural ambient environmental conditions. A series of PMFCs was deployed for three months to examine bioelectricity generation, soil water characteristics, and ambient environmental conditions, employing three vegetation types, providing an intricate understanding of the coupled bio-hydrological behaviors in the field. PMFC performance was further enhanced by heightened solar radiation and precipitation, amplifying bio-electrical output. However, a 72 %-89 % decline in electrical current and potential occurred at the air entry value due to disrupted ion transport which caused increased soil electrical resistance. This phenomenon underscores the intricate balance between ambient conditions and PMFC performance, laying a foundation for optimizing PMFCs for specific ecological and hydrological contexts. These findings emphasize the potential of PMFCs in real-time, in-situ reflecting of hydrological soil characteristics, offering an innovative approach to ecosystem management and hazard mitigation efforts.

This study investigates the effect of peach shell biochar on the unsaturated soil water retention characteristics, electrical conductivity (EC), and its correlation with the compressibility of poorly graded Fujian soil, thereby addressing a critical gap in biochar research for geotechnical applications. The study aims to explore an economical approach to accessing geotechnical properties using EC. Biochar (produced at 600 °C) was mixed with sand at 0

Soil salinity in Central Asia negatively impacts soil structure, leading to degradation and reduced water infiltration. This not only hampers agricultural productivity but also makes the land less suitable for construction due to its high susceptibility to deformation. Environmentally friendly materials like biochar, a carbon-rich substance, show promise in reducing the deformation of saline soils. However, the mechanisms behind its effectiveness are not yet fully understood. This study aims to analyse saline clays’ dispersion and sedimentation behaviour under varying pore water salinity levels (0 % to 10%). A biochar content of 5 % was selected as it is found to be optimum for plant growth and erosion resistance. It was found from the study that the biochar increases the aggregation of soil particles and enhances flocculation, improving soil dispersion characteristics. Biochar facilitates soil particle aggregation by increasing the cation exchange capacity. At higher pore water salinity levels (5% and 10%), the sedimentation behaviour of biochar-treated soil particles deviates from expectations, showing slower sedimentation rates and lower sedimentation heights. This is because the sodium ions are adsorbed by biochar, reducing salt’s effect on dispersion and sedimentation. The results demonstrate that biochar effectively enhances the stability of saline soils and, hence, has a potential use for ground improvement in the Central Asian region.

Water deficiency caused by climate change is a global challenge for food security. Viable sustainable alternatives for enhancing water storage in the soil is a necessity for arid and drought prone regions. Water-absorbing polymer (WAP) is capable of improving the water storage in soil pores, and its efficacy can be ascertained by evaluating the resilience of plants towards wilting. The main objective of this study was field demonstration on the usefulness of fly ash-based WAP (FA-WAP) in prolonging wilting and plant survival time of beans (Phaseolus vulgaris) and radish (Raphanus sativus) in a silt loam. This was achieved by following a novel methodology for determining plant permanent wilting point (PWP) by integrating both soil response (suction) and plant response (stomatal conductance and photosynthetic yield), as against the common practice of considering a reference negative water potential (or soil suction) value of 1500 kPa. Using the proposed methodology, the PWP was 1300 kPa and 1150 kPa for beans and radish, respectively. The measured soil water retention curves (SWRC) demonstrated higher water availability in the WAP-amended soil compared to the control soil for both plant species, thereby prolonging plant survival time. The presence of WAP positively influenced the plant biochemical parameters (such as H2O2, MDA, proline, CHL A+B) under water deficit conditions. The WAP amendment resulted in 2.3 and 1.4 times crop yield for beans and radish, respectively, compared to the unamended soil. The use of FA-WAP has a high potential to reduce the irrigation water demand without compromising the yield of two vegetable species considered in this study.

This study investigates the effects of three biochars-corn straw biochar (CSB), reed straw biochar (RSB), and applewood biochar (AWB)-on microbial communities and bioelectricity generation in plant microbial fuel cells (PMFCs) under unsaturated soil conditions. Biochars were incorporated at 5% mass ratio into silty lean clay soil planted with Hydrocotyle vulgaris, with bioelectricity, soil moisture, and microbial diversity monitored during drought simulation. Key results revealed that RSB-amended PMFCs achieved the highest power density (1608 mW/m2), surpassing AWB (730 mW/m2), CSB (63 mW/m2), and the control (52 mW/m2). RSB enhanced bioelectric potential and current by 4.5x and 23x, respectively, compared to the control, attributed to its high porosity (29.198 m2/g surface area) and microbial diversity (Chao1 = 888.09; Shannon = 8.09). AWB, despite lower microbial richness (Chao1 = 333.40), sustained bioelectricity via hydrophilic functional groups (& horbar;OH, & horbar;NH2), favoring Aeromonas dominance (45.87% abundance). Microbial analysis identified Proteobacteria (60.41%-74.66%) and Firmicutes (1.29%-12.89%) as key electroactive phyla, with genera Pseudomonas (up to 24.08%) and Aeromonas driving electron transfer. CSB exhibited intermediate performance, limited by lamellar pore structure and reduced microbial diversity (Shannon = 6.83). The findings demonstrate that biochar feedstock critically influences PMFC performance: RSB optimizes microbial diversity and electroactivity, while AWB leverages hydrophilicity for drought resilience. This study advances sustainable bioenergy strategies by linking biochar properties to microbial-electrogenic synergies, offering pathways to enhance PMFC efficiency in water-stressed environments.