Search Results (760)

Freshwater prawns are important components of freshwater ecosystems, yet their diversity and genetic structure in northeastern Thailand remain insufficiently documented, particularly across habitats differing in soil salinity. This study assessed freshwater prawn diversity and phylogenetic relationships in saline and non-saline habitats using an integrative taxonomic approach combining morphological examination with mitochondrial and nuclear DNA barcoding. A total of 225 mature specimens were collected from 15 sampling sites in Maha Sarakham province (saline habitats) and Mukdahan province (non-saline habitats). Representative specimens were examined morphologically and characterized using four barcode loci: cytochrome c oxidase subunit I (COI), 16S ribosomal RNA (16S rRNA), 18S ribosomal RNA (18S rRNA), and the internal transcribed spacer (ITS). Morphological assessment identified three taxa, Macrobrachium lanchesteri, Macrobrachium niphanae and Caridina sp. Molecular analyses recovered three principal lineages broadly corresponding to these taxonomic groups, although the resolution varied among loci. COI provided consistent species-level discrimination, while 16S rRNA revealed additional genetic variation within Macrobrachium. The conserved 18S rRNA marker supported separation of the major taxonomic lineages, whereas ITS contributed complementary sequence variation for lineage assessment. The concatenated multilocus dataset provided the most stable phylogenetic reconstruction, with strong support for the principal lineages. Samples from saline and non-saline habitats were not consistently separated, suggesting that salinity was not the primary factor underlying the observed genetic structure. Overall, integrating morphological and multilocus molecular evidence provided a robust framework for assessing freshwater prawn diversity and phylogenetic relationships and establishes a baseline for future taxonomic, phylogeographic, and conservation studies in the Mekong region. Full article

Cicer grande (Popov) Korotkova is a rare, subendemic species within the flora of Uzbekistan, primarily inhabiting mountainous landscapes. As a wild progenitor of nutritionally significant cultivated crops, it holds considerable potential for enhancing food security and mitigating hunger through applications in sustainable agriculture and the conservation of plant genetic resources. This study employed species distribution modeling to examine the ecological niche, geographic distribution, and potential habitat suitability of C. grande across Uzbekistan. Data from herbarium specimens and field surveys were integrated with a comprehensive suite of environmental variables encompassing climatic, edaphic, topographic, hydrological, and anthropogenic factors. From an initial set of 45 predictor variables, highly correlated ones were removed using Pearson correlation analysis and variance inflation factor (VIF) assessment to reduce multicollinearity. Habitat suitability was subsequently modeled using the BIOCLIM algorithm. The results show that C. grande is predominantly found at elevations between 1000 and 2500 m, where it is strongly associated with shallow Lithosols and carbonate-rich Calcic Xerosols (FAO soil classification). Phytocoenotic assessments indicate that the species occurs mainly within plant communities dominated by perennial species. Among the environmental drivers analyzed, elevation, temperature-related variables, and slope aspect were identified as the most influential factors shaping its distribution. BIOCLIM projections reveal that highly suitable habitats are spatially limited and largely confined to the Nurata and Kuhitang mountain ranges. Overall, these findings demonstrate that C. grande occupies a narrow and specialized ecological niche, which likely accounts for its restricted distribution and subendemic status. This study provides a robust scientific foundation for developing conservation strategies and habitat management plans for this rare species in Central Asia. Full article

Slope stability in vegetated hillslopes depends on groundwater, geometry, external loading, soil properties, and root reinforcement. This study evaluated a low-plasticity clayey silt (CL–ML) from Loja, Ecuador, under bare soil, Eucalyptus, Pine, Vetiver, and Kikuyu covers. Direct shear tests on root-containing specimens provided equivalent Mohr–Coulomb parameters for limit-equilibrium and PLAXIS 2D strength-reduction analyses considering three slope geometries and three loading conditions: elevated groundwater, groundwater plus an 8 kN m⁻² surcharge, and groundwater, surcharge, and pseudo-static loading. The resulting 90 factor-of-safety values were assessed using scenario-based factorial ANOVA and MANOVA. Geometry and loading explained 41.4% and 35.0% of total variance, respectively, whereas numerical method explained 1.1%. Limit-equilibrium factors of safety were 5.4% higher on average than PLAXIS 2D values. The vegetation-cover main effect was small and marginal (η² = 1.5%, p = 0.051), while significant cover–loading and cover–method interactions indicated a scenario- and method-dependent response. Under pseudo-static loading, Vetiver and Kikuyu showed the highest PLAXIS 2D factors of safety, whereas LEM results remained narrowly grouped, precluding a general ranking of vegetation effectiveness. These findings support scenario-specific evaluation of equivalent root reinforcement in slope-stabilization design. Full article

Problematic fine-grained soils exhibit low strength and inadequate durability, highlighting the need for sustainable stabilization using eco-friendly binders. This study examined the strength development and durability of a natural CH soil (NSs) stabilized with fly ash (FA) based geopolymer exposed to sulfate attack and freeze–thaw (F–T) cycles. The effects of FA content (0–40%) and NaOH molarity (0–10 M) on unconfined compressive strength (UCS) were evaluated after 1, 7, 28 and 56 days of curing. Durability was assessed separately under accelerated laboratory conditions after 1, 3, 5, 7 and 11 F–T cycles and 7, 28 and 56 days of sulfate exposure. In non-activated specimens, FA contents of up to 30% enhanced the UCS primarily through the microfiller effect and possible time-dependent pozzolanic reactions. Alkali activation promoted the development of a compact binding matrix through the dissolution and polycondensation of aluminosilicate precursors, with the microstructural and chemical observations being consistent with the possible formation of C-(A)-S-H and/or N-A-S-H-type reaction products. F30M8 exhibited the highest strength, reaching a 56-day UCS of 1488.58 kPa compared with 282.46 kPa for untreated NSs. F30M8 retained approximately 94% of its UCS after 11 F–T cycles and 92% after 56 days of sulfate exposure. XRD, FTIR, and SEM-EDX analyses provided evidence of aluminosilicate restructuring and the development of a dense microstructure under alkaline activation. This refined matrix may have contributed to limiting sulfate- and ice-crystal-induced deterioration, thereby helping to preserve the structural integrity of the FA-based geopolymer-stabilized NS specimens, whereas untreated and non-activated FA-stabilized specimens disintegrated under sulfate exposure. These findings indicate that FA-based geopolymer stabilization has considerable potential for natural CH soil under the laboratory exposure conditions investigated in this study. Full article

The laboratory fall-cone (FC) test method is widely adopted for liquid limit LL_FC determination, and in undrained shear strength s_u measurement of very soft to firm fine-grained soils. Additionally, it is used to establish the PL₁₀₀ parameter (i.e., the water content w mobilizing a 100-fold s_u increase relative to the LL_FC strength), typically determined using LL_FC data extrapolation approaches. This paper presents a theoretical and data-reanalysis investigation into the application of drop-cone (DC) methods for s_u measurement of firm to stiff fine-grained soils, and their PL₁₀₀ determination. Here, a 30° or 60° cone of modest mass M, released from a drop height h_d, contacts the test-specimen surface with an impact velocity, and penetrates into the soil, before coming to its rest position for a cone penetration depth d. Based on previously reported experimental FC and DC d:w data for ten different fine-grained soils, the authors examined the effects of (i) frictional resistance between the stem of the falling DC and its guide bearing, and (ii) the DC’s higher soil deformation rate, on the deduced PL₁₀₀ water content. An adjusted cone-factor framework for DC s_u testing, which considers the h_d/d ratio, and higher soil deformation rate, is presented. Bearing friction has the effect of deducing slightly higher s_u and PL₁₀₀ values. Small calibration adjustments to the DC setup, namely marginally increasing (i) the cone mass M, (ii) the drop height h_d, or (iii) both M and h_d, can eliminate systematic overpredictions. Theoretical 30° and 60° DC M:h_d combinations are identified for PL₁₀₀ determination. Finally, LL_FC data extrapolation for PL₁₀₀ determination, employing the bi-logarithmic log₁₀d:log₁₀w model, was found to achieve moderate levels of agreement between predicted PL₁₀₀ values and those directly measured using an 8 kg/30°–0 mm contacting cone for d = 20 mm, raising possible concerns about the generalizability of the extrapolation approach. Full article

Dispersive soils are widely distributed in the seasonally frozen regions of northeastern China, where hydrothermal dynamics driven by seasonal freeze–thaw (FT) cycles dominate the hydrological evolution and mechanical deterioration of soil masses, posing a serious threat to the long-term stability of hydraulic engineering in cold regions. However, the hydro–thermo–mechanical (HTM) coupled degradation mechanisms of dispersive clay from the South Nenjiang Main Canal remain poorly understood, particularly the linkage between FT-induced microstructural evolution and macroscopic mechanical behavior. In this study, low-plasticity dispersive clay specimens were subjected to 0–12 FT cycles. Unconsolidated undrained (UU) triaxial tests were conducted to evaluate mechanical behavior, while scanning electron microscopy (SEM) combined with the Pore and Crack Analysis System (PCAS) was used to quantify microstructural evolution. Results indicated that increasing FT cycles transformed the stress–strain response from mild strain-softening to strain-hardening, with the failure mode evolving toward bulging-type ductile failure. Cohesion exhibited a pronounced exponential decay, with the most significant degradation occurring within the first three FT cycles and stabilizing after approximately six FT cycles, whereas the internal friction angle showed only minor variation. At the microscale, porosity and total pore area increased continuously through micropore coalescence and macropore development, with a slight decrease in fractal dimension indicating reduced pore boundary complexity and smoothed pore interfaces due to frost heave-induced pore merging. The FT-induced hydrothermal disturbance promoted pore-water phase transition and redistribution, resulting in progressive pore enlargement and loss of structural integrity. Because the specimens were tested in sealed, closed-system conditions with a nearly constant total water content, this degradation chain is attributable specifically to in situ ice–water phase transitions and internal pore-water redistribution, i.e., water-phase-change-driven processes, rather than to external water supply. It is demonstrated that interparticle bond breakage and pore expansion–coalescence driven by ice–water phase transitions dominate strength degradation, promoting a transition from structure-dominated to friction-dominated strength behavior. A normalized cohesion reduction factor and a cohesion degradation index are further proposed to quantify the progressive loss of structural integrity and to provide a design-oriented tool for cold-region geotechnical practice. These findings provide a basis for stability assessment and hazard mitigation of dispersive soils in cold-region engineering. Full article

A sustainable controlled low-strength material (CLSM) was developed using ground granulated blast-furnace slag, steel slag, and flue gas desulfurization gypsum in combination with cement to synergistically utilize engineering excavated soil and industrial solid wastes for stabilizing low liquid limit clay. However, the long-term durability evolution of this material under harsh and coupled environmental conditions—particularly freeze–thaw cycles, wet–dry cycles, and prolonged drying—has not been systematically investigated. In this study, systematic freeze–thaw cycling (up to 11 cycles), wet–dry cycling (up to 11 cycles), and natural drying (until mass stabilization) tests were conducted on specimens with binder contents ranging from 8% to 16%. The evolution of mechanical performance was evaluated via unconfined compressive strength (UCS) tests, while microstructural changes were characterized using scanning electron microscopy (SEM) and X-ray diffraction (XRD). The results revealed a distinctive “S-shaped” fluctuation in UCS under freeze–thaw cycles. High-binder (16%) specimens maintained strengths of 1783–2395 kPa with intact surfaces and no visible cracking—significantly outperforming low-binder specimens. Under wet–dry cycles, strength initially increased after the first cycle and then declined progressively, with the lowest strength loss observed at 10% binder content. During drying, both water loss rate and drying shrinkage strain decreased with increasing binder content: from 8% to 16% binder, the water loss rate dropped from 34.16% to 29.03%. Microstructural analysis revealed that higher binder content promoted the formation of a dense, interwoven network of C–S–H gel and ettringite, which effectively filled intergranular pores and encapsulated soil particles, thereby enhancing macroscopic durability. This study provides a sustainable material solution for utilizing industrial solid wastes in the stabilization of low liquid limit clay for CLSM applications under severe environmental conditions, supporting the broader adoption of waste-to-resource strategies in construction engineering. Full article

Two paradigms dominate the literature on resilient strain behaviour of unbound granular materials (UGMs): empirical formulations, often lacking theoretical grounding, and machine learning (ML) models, operating as black boxes. This study proposes a hyperelastic strain energy potential—the KHP (Karasahin Hyperelastic Potential) model—deriving its volumetric component from the logarithmic compression relationship of critical-state soil mechanics and its shear component from a power-law distortional term. Analytical differentiation yields strains that inherently satisfy Maxwell’s symmetry, guaranteeing thermodynamic consistency. The model was calibrated to repeated-load triaxial data from sand-and-gravel and crushed limestone specimens and evaluated using Leave-One-Out Cross-Validation against three empirical models and two ML algorithms (Gaussian Process Regression, GPR, and a Neural Network). For axial strain, KHP ranked second only to GPR; for radial strain, it achieved the highest accuracy across both materials, outperforming all ML models. Its practical value was shown through a nonlinear finite element analysis of a flexible pavement section, reproducing the stress-dependent resilient behaviour of the base layer as a numerical demonstration of engineering usability, rather than a validation against measured field response. These findings show that a physical hyperelastic framework can match or exceed machine learning accuracy while preserving thermodynamic consistency, interpretability, and generalisability. Full article

The presence of antimicrobial-resistant bacteria in fresh produce constitutes a significant public health concern, particularly in rural areas where untreated water is commonly used for irrigation. Certain Enterobacter species have been reported as causal agents of onion bulb rot, with Enterobacter cloacae experimentally demonstrated to cause bulb rot in onions. However, there is poor documentation of its effects in the Vhembe District, South Africa. This study investigated the detection and identification of enteric bacteria in onions, soil, and irrigation water, as well as the characterisation of the identified isolates. Thirty-six samples were analysed, comprising 13 onion samples, 4 irrigation water samples, and 9 soil specimens collected from three farms using selective and differential agar. Identification and enumeration in water and onion samples were performed with the Colilert Quanti-Tray. Physicochemical analysis of irrigation water indicated that Farm 3 had the highest electrical conductivity (EC) and total dissolved solids (TDS), as well as the lowest pH, while Farm 2 exhibited the greatest diversity of pathogenic Escherichia coli pathotypes, including enteroinvasive E. coli (EIEC), which was absent in Farm 3. Culture-based methods yielded 72 presumptive bacterial isolates, which were characterized using the VITEK 2 system. Identified species included Pseudomonas aeruginosa, Klebsiella pneumoniae, Klebsiella oxytoca, Citrobacter amalonaticus, Raoultella ornithinolytica, and members of the Enterobacter cloacae complex. Phylogenetic analysis revealed that most Enterobacter isolates closely matched reference strains of Enterobacter ludwigii. Antimicrobial susceptibility testing against 19 antibiotics demonstrated varied resistance patterns among the isolates. The Enterobacter cloacae complex exhibited the highest resistance (10/19 antibiotics), followed by Klebsiella pneumoniae (9/19) and Citrobacter amalonaticus (7/19). All isolates were resistant to colistin but remained susceptible to ciprofloxacin, with most also sensitive to gentamicin and amikacin. Future research should include additional farms and investigate antibiotic resistance at the genetic level to elucidate its origins. Full article

Monthly dynamics of ground-dwelling beetles remain poorly resolved in agro-pastoral ecotones. From June to September 2025, beetles were sampled monthly with pitfall traps in 81 permanent 1 m × 1 m quadrats across nine plots representing temperate steppe, temperate desert steppe, and lowland meadow in the Tacheng Basin, Xinjiang, China. Specimens were identified to family, and analyses used family-level data. Assemblage composition varied significantly among months, whereas neither the overall habitat effect nor the habitat × month interaction was significant. Habitat × month interactions were significant for total beetle activity-density and for Tenebrionidae, Scarabaeidae, and Carabidae activity-density. Tenebrionidae dominated catches in July and August, whereas Scarabaeidae contributed the largest proportions in June and September. Significant within-month habitat contrasts in diversity metrics were detected only for Margalef richness in June. Neither distance class nor the distance class × month interaction was significantly associated with activity-density, diversity metrics, or assemblage composition. After conditioning on plot identity and month, measured vegetation and soil variables did not significantly explain residual assemblage variation. These findings highlight pronounced monthly turnover and the value of repeated sampling across months during the June–September period. Full article

Rainfall-induced seepage instability is a major concern for internal waste dump slopes in cold-region open-pit coal mines, where slope performance is influenced by groundwater conditions, moisture state, and seasonal temperature variations. This study investigates the internal waste dump slope of the Chaoyang open-pit coal mine and evaluates its seepage and stability responses under prescribed moisture and temperature states before and after rainfall, together with the effectiveness of drainage control. Soil specimens with moisture contents of 14%, 17.6% (natural), 23%, and 26% were tested at ambient temperature, −5 °C, and −15 °C by uniaxial compression and direct shear tests. The mechanical parameters measured under the prescribed moisture and temperature states were assigned to a GTS NX seepage–stability model. Twenty-four parametric cases, comprising four moisture contents, three temperature states, and pre- and post-rainfall conditions, were evaluated using the strength-reduction method, and an HDPE perforated drainage scheme was subsequently assessed. Under the ambient-temperature parameter state, increasing specimen moisture content from 14% to 26% reduced the pre-rainfall factor of safety from 1.41 to 1.18 and the post-rainfall value from 1.38 to 1.17. Parameter sets obtained from low-temperature-conditioned specimens produced higher calculated factors of safety; however, these cases represent prescribed mechanical states rather than the actual winter condition of the full-scale slope. Under the idealized drainage boundary, the pre- and post-rainfall factors of safety increased from 1.22 and 1.18 to 1.40 and 1.39, respectively. The results demonstrate the relative effects of laboratory-derived mechanical parameters, rainfall-induced seepage, and idealized drainage under the prescribed scenarios. Full article

When red-bed mudstone is directly used as fill material for building foundations, road subgrades, and similar applications, it is prone to seepage-induced deformation and instability. Amending it with montmorillonite bentonite can effectively regulate its permeability characteristics. Meanwhile, rapid and accurate prediction of the permeability coefficient is crucial for building foundations and road subgrade seepage analysis and stability assessment. This study investigated red-bed mudstone fill material modified with montmorillonite bentonite at different blending ratios. Soil–water characteristic curve tests, saturated/unsaturated permeability tests, and nuclear magnetic resonance (NMR) tests were conducted on the specimens to examine the pore evolution patterns and permeability characteristics of the modified red-bed mudstone, and a predictive model for coefficients was proposed. The results indicate that the incorporation of montmorillonite-based bentonite markedly affects the permeability properties of modified red-bed mudstone fillers. The NMR T₂ spectrum exhibits a bimodal distribution; the incorporation of bentonite and the saturation process result in a marked reduction in large pores and an increase in microporosity. The predictive model achieves higher accuracy when the montmorillonite bentonite content is high. Sensitivity analysis revealed that the maximum pore radius has a far greater influence on permeability than the pore fractal dimension and tortuosity. The research findings provide experimental evidence and theoretical models for the rapid estimation of permeability and seepage stability analysis of modified red-bed mudstone fill materials. Full article

This study evaluates the effectiveness of water-soluble epoxy resin for stabilising clay soils in the design of column-type reinforcement in soft ground. To evaluate the influence of varying mix proportions of epoxy resin on the strength of a stabilised silty clay soil, specimens were subjected to a series of unconfined compression tests at various curing ages. In addition, undrained unconsolidated, isotropically consolidated undrained, and isotropically consolidated drained triaxial tests were conducted on specimens after 180 days of curing. Finally, the dynamic behaviour of the treated soil was investigated via isotropically consolidated undrained cyclic triaxial testing. Furthermore, the effect of incorporating epoxy resin on the key physical properties was assessed via water permeability, porosity, and viscosity measurements. The experiments showed that the use of this resinous material resulted in an appreciable increase in all strength values. Moreover, all stabilised specimens exhibited a substantial improvement in cyclic properties, with failure occurring at significantly elevated stress levels and after enduring a larger number of loading cycles, compared to their untreated counterparts. The laboratory results presented here offer critical guidelines for future experimental studies aimed at improving the efficacy of this material in the chemical treatment of weak soils and deep soil mixing applications. Full article

A carbide-slag-activated slag-fly ash geopolymer (CSF) and waste gold tailings sand were used to co-stabilize mucky soil, aiming to promote the valorization of multiple industrial solid wastes and provide a low-carbon treatment approach for mucky soil in river and lake regions. Unconfined compression, direct shear, water stability, scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy (SEM-EDS), and heavy metal leaching tests were conducted to investigate the effects of CSF and gold tailings sand contents on the mechanical properties, water stability, microstructure, and environmental safety of the stabilized soil. The results showed that the unconfined compressive strength (UCS) and shear strength increased with increasing CSF content, whereas the strength gain became marginal when the CSF content exceeded 15%. With the CSF content fixed at 15%, both the strength and water stability initially increased and then decreased as the gold tailings sand content increased. The CSF15-G30 specimen exhibited favorable overall performance, with 7 d and 28 d UCS values of 0.65 and 1.53 MPa, respectively, representing increases of 25.0% and 12.5% relative to CSF15. Its cohesion and internal friction angle reached 88.21 kPa and 47.13°, corresponding to increases of 44.5% and 8.1%, respectively. The water stability coefficients at 7 d and 28 d were 76.9% and 87.6%, respectively. SEM-EDS observations indicated that the cementitious products generated by CSF, together with the filling and skeletal effects of gold tailings sand, enhanced interparticle bonding and matrix densification. Although the concentrations of leached heavy metals increased with increasing gold tailings sand content, all measured values remained below the relevant leaching-toxicity limits. These results demonstrate that an appropriate amount of gold tailings sand can effectively improve the mechanical properties and water stability of CSF-stabilized mucky soil while maintaining satisfactory environmental compatibility. Full article

Traditional cement-based foamed lightweight soils suffer from high construction costs, poor durability, and low solid waste utilization efficiency, which severely restrict their engineering application. A novel polyvinyl alcohol (PVA)-reinforced solid waste-based foamed lightweight soil is fabricated using Bayer red mud, mineral powder, and fly ash. To clarify the durability evolution mechanisms, systematic freeze–thaw cycling, long-term water immersion, and sodium sulfate erosion tests were conducted on PVA-reinforced solid waste-based, unreinforced solid waste-based, and pure cement-based specimens. The results demonstrate that the PVA-reinforced specimen achieves optimal freeze–thaw resistance with only 17.10% strength loss after 50 cycles, owing to the internal three-dimensional fiber network that restrains crack propagation and enhances matrix toughness. It also exhibits excellent long-term water immersion stability, with a mild strength increment of 4.04–10.33% after 120 days. In contrast, the CN exhibited a strength increase of 43.62%, attributed to its lower initial strength caused by incomplete hydration; however, its final strength remained between those of the other two groups. In sulfate environments, unreinforced solid waste-based specimens present superior corrosion resistance, while PVA fiber-induced interconnected pores slightly weaken sulfate erosion resistance. Microscopic analysis confirms that the generation of alunite and gypsum hydration products fundamentally causes performance discrepancies among different specimens. Different from previous studies focusing on single fiber modification or single solid waste partial replacement of cement, this study innovatively adopts a composite modification strategy of “multi-solid waste alkali-activated matrix + PVA fiber toughening”, and systematically reveals the durability evolution mechanism under multiple harsh environments. Full article