Search Results (3,486)

Permeability anisotropy, which is widely present in natural soil deposits, plays an important role in controlling groundwater flow patterns and ground deformation during deep excavation dewatering. However, isotropic assumptions are still commonly adopted in engineering practice, making it difficult to accurately capture realistic subsurface hydraulic conditions. In this study, a deep foundation pit of a metro station in Jinan, China, is taken as a case study. A three-dimensional excavation–dewatering model incorporating permeability anisotropy is established using PLAXIS 3D to systematically investigate the influence of the permeability ratio (Kx/Kz) ranging from 0.1 to 10 on the seepage field evolution, dewatering influence radius, ground surface settlement, and consolidation time history. The results indicate that increasing permeability anisotropy promotes a fundamental transition of the seepage regime from vertically concentrated recharge to laterally dominated radial flow. Correspondingly, the dewatering influence radius exhibits a pronounced non-monotonic response to Kx/Kz, decreasing significantly with increasing permeability ratio and reaching a minimum at approximately Kx/Kz ≈ 5, followed by a slight rebound. Meanwhile, surface settlement profiles evolve from a localized concentration pattern to a widely distributed form as permeability anisotropy increases, accompanied by a remarkable outward expansion of the settlement influence zone. Both the magnitude and spatial distribution of settlement show high sensitivity to variations in permeability anisotropy. Based on these findings, a three-stage conceptual seepage structure model accounting for permeability anisotropy is proposed, characterized by vertically dominated flow, a transitional competition regime, and horizontally dominated flow. The staged evolution of seepage structures is shown to govern the non-monotonic variation in the dewatering influence radius and the spatial–temporal response of ground settlement. The results indicate a dual-scale influence mechanism of permeability anisotropy on dewatering-induced hydro-mechanical behavior, providing a theoretical basis for refined dewatering design and environmental impact assessment in deep excavation projects. Full article

Biochar amendment holds promise for improving saline soils, yet its efficacy is often constrained by the uncertainty of application rates. In this study, a large field trial and associated statistical modeling were conducted to explore the mechanisms by which biochar affects wheat yield in coastal saline soils of northern China. Results showed that biochar application significantly increased soil organic carbon (SOC) content (R²= 0.615, p < 0.001) but induced marked spatial heterogeneity across the field, with the coefficient of variation (CV) reaching 30.2%. Given the difficulty of uniformly applying biochar in the field, subplot-level SOC was used as a proxy for effective biochar distribution. Stepwise regression identified soil electrical conductivity (EC) as the dominant yield constraint (standardized coefficient = −0.69), rather than water and nutrients, and a quadratic relationship was observed between SOC and EC. Structural equation modeling (SEM) further suggested a trade-off: SOC was associated with higher yield through reduced bulk density (BD) (path coefficient = −0.603), whereas high SOC levels were also associated with increased EC under this coastal saline field setting (path coefficient = 0.243), thereby indirectly constraining growth. Consequently, the agronomic response showed a threshold-like transition: the peak wheat yield occurred at an SOC threshold of 13.87 g kg⁻¹ (equivalent to 44.41 t ha⁻¹), which exceeded the point of minimum salinity (11.71 g kg⁻¹, equivalent to ~29.90 t ha⁻¹ biochar). These results suggest that the agronomic benefit of biochar in saline soils depends on maintaining application within an estimated beneficial buffering zone. Full article

This study investigates the influence of design factors and key process parameters—including explosive welding (EXW), rolling, and laser processing—on the formation, microstructure, and tribological properties of Ti–Cu–Ni intermetallic coatings. A combined manufacturing approach was employed, starting with the EXW of an MN19 cupronickel alloy to a VT1-0 titanium substrate, followed by multi-pass rolling to achieve a cladding thickness of approximately 0.3 mm. Subsequently, laser surface remelting was performed to facilitate controlled mass transfer and homogenization within the reaction zone. Numerical simulation using COMSOL Multiphysics v. 5.4 was utilized to optimize the thermal cycles and determine the ideal energy density (42 J/mm²) for phase formation. The results demonstrate that the primary structural components of the coatings produced under optimal conditions are solid solutions based on the ternary-modified titanium cuprides Ti₂Cu(Ni) and TiCu(Ni). The transition from a layered bimetal to a finely dispersed intermetallic structure significantly enhances the surface characteristics. This specific phase composition provides a sustained microhardness of ~5 GPa across the coating cross-section. Comparative wear tests against fixed abrasive revealed that the wear resistance of the Ti–Cu–Ni coatings is 2.5 times higher at room temperature and 1.5 times higher at 600 °C than that of the base VT1-0 titanium. Full article

Polyaniline-cadmium sulfide-gold (PANI-CdS-Au) nanocomposites were synthesized with varying Au loadings (0.023, 0.046, 0.092 wt%) to enhance antibacterial performance. Structural (FTIR, XRD) and morphological (FESEM) analyses confirmed successful formation, with nearly homogeneous nanoparticle distribution (27–53 nm) and slight XRD peak shifts indicating interfacial interactions between PANI, CdS, and Au. UV–Vis spectra revealed gold surface plasmon resonance and polaronic transitions consistent with PANI emeraldine base. XRD results showed the expected wurtzite CdS and fcc Au phases. Agar well diffusion tests against Escherichia coli (Gram-negative) and Staphylococcus aureus (Gram-positive) demonstrated that the 0.092 wt% of Au composite produced the largest inhibition zones at 100 µg mL⁻¹ (E. coli: 36 mm; S. aureus: 24 mm), with the same trend at 25 µg mL⁻¹. The results indicate that PANI–CdS/Au nanocomposites are promising antibacterial materials; however, the presence of CdS necessitates additional cytotoxicity assays to confirm their suitability for medical applications. Full article

Oceanfront relief varies along coastlines and serves as the first barrier to wave and surge damage. However, forecasted increases in storm frequency and sea levels are anticipated to enhance coastal erosion, potentially weakening this protection. The land–sea transition is variable along the New England coast, USA, and this variability has produced a range of coastal morphologies that can vary over short distances. It is important to track the beach transition zone to better understand transformations of the system and related hazard risks. A combination of field and computer-based methods was used to evaluate the beach transition zone of southwestern Rhode Island to determine alongshore variability and dynamics. More specifically, a decadal-scale study was conducted to examine changes in morphology from 2011 to 2022, and a short-term study at South Kingstown Town Beach examined changes from November 2023 to January 2024 using time-series drone-derived elevations. Classification of over 500 cross-shore transects illustrated the dominance of sedimentary shorelines, with smaller areas of rocky outcrops and hardening. Analysis of four different years (2011, 2014, 2018, and 2022) determined that beaches with dune morphology were the most common type of transition zone (41–47% of the transects) and transects with a high bank upland were the next most frequent class (34–41%). Following Hurricane Sandy in 2012, a 6% decrease in the number of dune-classified transects was measured; however, one-third of those recovered dune morphology by 2022. The greatest beach transformations over the short-term study occurred in response to strong storms in the 2023–2024 winter season, during which lateral beach movement (erosion) exceeded 15 m in portions of South Kingstown Town Beach. Dune erosion was accompanied by overwash flooding and deposition, and the area remained low-lying and thus vulnerable to future impacts. The beach transition zone classification and insights from this research will be informative for future planning by coastal communities by determining at-risk shorelines based on underlying geology and the stability of morphological features. Full article

Alpine treeline and shrubline ecotones are climatically sensitive transition zones where vegetation shifts strongly influence belowground microbial processes. Soil bacteria and fungi, as core component of the soil microbiome, play vital roles in nutrient cycling and plant–soil interactions within these fragile ecosystems. However, the structure and diversity of soil microbial communities across the treeline–shrubline transition remain poorly understood. Here, we investigated soil bacterial and fungal communities across treeline and shrubline ecotones in two mountain on the eastern Tibetan Plateau. We further examined how soil physicochemical properties shaped microbial community assembly. Our results demonstrated that the community composition of both bacteria and fungi differed significantly between the treeline and shrubline ecotones, while the Shannon index showed no significant variation. At the phylum level, Proteobacteria, Actinobacteriota, and Acidobacteriota dominated bacterial communities, while Ascomycota and Basidiomycota were the predominant fungal phyla. Both the network complexity of soil bacterial and fungal communities changed significantly across ecotones. Specifically, bacterial network complexity increased significantly toward the shrubline, whereas fungal network complexity declined. Bacterial community compositions were co-regulated by both environmental and vegetation factors, while fungal community compositions were only regulated by soil pH. Redundancy analysis revealed that soil organic carbon, pH, and moisture were the primary drivers of bacterial community (38.17%), whereas vegetation cover, soil organic carbon, and moisture explained the largest proportion of fungal community (44.79%). Our findings reveal the distribution patterns and underlying shift mechanisms of microbial communities between the treeline and shrubline ecotone. These insights are crucial for mountain biodiversity conservation and for improving predictions of forest responses to climate change. Full article

The Alborz Mountain range, serving as the strategic water tower of the Iranian Plateau, is experiencing the accelerating impacts of climate change. Given the critical role of snow reserves in this region for water security, understanding the mechanisms of snow degradation in response to warming is essential. Aiming to investigate the divergent responses of snow cover and snow depth to extreme temperature indices, this study analyzes a 23-year time series (2001–2023) of ERA5-Land data and MODIS imagery across 11 elevation bands. To this end, trends and correlations among the Warm Spell Duration Index (WSDI), the Percentage of Warm Days (TX90p), the Normalized Difference Snow Index (NDSI), and Average Snow Depth (ASD) were assessed using the Modified Mann–Kendall (MMK) test, Generalized Linear Modeling (GLM), and Spearman’s rank correlation. The findings reveal elevational heterogeneity in the snow regime of the Alborz. Notably, the decline in spatial snow cover (NDSI) is primarily concentrated in the mid-elevation transition zone (2000 to 3000 m), whereas the reduction in snow depth (ASD) is a widespread phenomenon, observed even at high altitudes above 4000 m. A key innovation of this research is demonstrating the dominant role of heat frequency over heat duration; GLM results indicate that the TX90p index (frequency of warm days) has a much stronger negative correlation with the degradation of snow resources than WSDI. These results confirm the transition of the Alborz hydrological system toward instability, the upward shift in the snowline in the transition zone, and the invisible thinning of the snowpack at higher elevations. Full article

In order to explore the outstanding problems, such as poor mechanical performance, of recycled aggregate from construction waste in the application of backfills, this study innovatively used accelerated carbonation treatment technology to pretreat the recycled aggregates, and systematically investigated the evolution of mechanical properties in carbonated recycled aggregate-based cemented paste backfill (CPB). By carbonizing the waste recycled concrete aggregate (RCA), carbonation recycled concrete aggregates (CRCA) were obtained, and coal gangue was replaced as the filling aggregate at 50% and 100% for mine paste filling. The mechanical properties of the CPB were measured, and the mechanism was analyzed in combination with the changes in the microstructure. The results showed that the physical properties of RCA were significantly improved by carbonation treatment compared with untreated raw RCA: the apparent density of C₆₀d-RCA increased by 2.88% relative to non-carbonated RCA, while its crushing value decreased by 51.45%, resulting in a more stable aggregate structure. In terms of mechanical properties, the compressive strengths of the 28day carbonated backfills with 50% and 100% CRCA contents (denoted as C₂₈d-RCA-50 and C₂₈d-RCA-100) reached 6.38 MPa and 5.32 MPa, representing increases of 61.52% and 46.33%, respectively, compared to the control group. Microstructure and phase composition analysis showed that the carbonation reaction not only produced calcium carbonate (CaCO₃) crystals to effectively fill the internal pores and reduce the total porosity of the matrix, but also promoted the generation of monocarboaluminate and provided abundant nucleation sites for calcium silicate hydrate (C-S-H) gel hydration, which significantly optimized the structure of the interfacial transition zone (ITZ) and improved its microhardness. Among all test groups, the CRCA-50 group showed the most optimized microstructure and the best mechanical properties. This study provides a theoretical reference for the resource utilization of this type of 30-year service life RCA in mine filling. Full article

Urban infrastructure works conducted under live traffic conditions often face a persistent gap between approved traffic management plans and their actual field implementation. This gap remains underexplored in longitudinal studies, particularly in utility projects from low- and middle-income urban contexts. This study evaluates a risk-based supervisory approach that integrates daily monitoring of the Traffic Management Plan (TMP) with a corporate risk management framework aligned with ISO 31000. The dataset includes 288 supervised workdays over 16 months (November 2023–February 2025), 99 non-conformity tickets, 96 signal-theft events (137 units), and seven traffic incidents. The analysis combines descriptive statistics, hypothesis testing, logistic regression, segmented longitudinal analysis, count models, response-time evaluation, and a composite risk index. TMP non-compliance decreased from 18.8% to 6.9% between the first and second halves of the study period ($p=0.0028$). The odds of non-compliance were significantly higher during the staff transition period in April–May 2024 (OR = 3.50; 95% CI: 1.24–9.82), while day and night shifts showed comparable rates. Monthly patterns indicate that staff instability and signal theft contributed to non-compliance levels, and ticket resolution remained slow (mean response time: 69.9 days). These findings highlight the importance of supervisory continuity, contractor stability, and timely corrective actions in improving work zone safety. Full article

The present paper addresses the experimental measurement of vibration frequencies using an earth pressure sensor embedded in a full-scale (1:1) test structure. The vibration frequencies within the tested structure were induced by static load tests carried out at different elevation levels (corresponding to varying thicknesses of the crushed aggregate layer) in accordance with the methodology applied on German railways (DIN 18 134). The aim of the research was to verify the stress state at individual partial levels of the tested structure on the basis of the measured vibration frequencies, and to determine the depth of influence and the load dispersion angle generated by the static load test (SLT). The measured parameters also serve as input data for parallel research focused on the assessment of transition zones between railway embankments and artificial structures along railway lines. The results presented in this paper indicate that the stress induced by the SLT decreases with increasing structural thickness of the tested construction. For a structural layer thickness of 150 mm, the resulting stress corresponds to approximately 63% of the stress value (force effect) induced on a rigid circular plate (σ = 0.50 MPa), whereas for a layer thickness of 900 mm, the stress corresponds to approximately 12% of that value. The force (stress) effects of the SLT cease to act at a depth between 900 and 950 mm (only stress due to the self-weight of the overlying material was recorded), and the load dispersion angle is approximately 40°. Full article

Understanding the long-term dynamics of cropland water use efficiency (WUE) and its underlying environmental drivers is essential for ensuring food and water security, particularly for regions facing intensified climate change. Here, we investigated the spatial patterns and long-term trends of gross primary productivity (GPP), evapotranspiration (ET), and WUE in cropland ecosystems across Northeast China during the past two decades as the nation’s primary commodity grain base using the time-series Breathing Earth System Simulator (BESS) products. Subsequently, the ridge regression method was used to quantitatively disentangle the relative contributions of key climatic variables to the observed WUE trends of cropland. Our results revealed a pronounced decreasing gradient in both GPP and ET along the southeast–northwest direction. A significant increase in GPP was observed over the 20-year period (p < 0.01), with 95.94% of the cropland area showing positive trends. ET showed a slight, non-significant increase (p > 0.05), though 82.77% of pixels exhibited positive trends, particularly in the northwest. Consequently, WUE showed a widespread and significant enhancement (p < 0.01), with approximately 98% of cropland pixels exhibiting increasing trends. Attribution analysis identified air temperature as the dominant environmental variable, accounting for 92.4% of the observed WUE increase, while solar radiation and precipitation contributed modestly (3.4% and 3.2%, respectively). Our findings underscore the predominant role of thermal conditions in shaping the carbon–water coupling efficiency of agroecosystems in semi-arid to semi-humid transition zones. This study provides quantitative evidence that warming climate, rather than changes in water availability or radiation, has been the primary climatic factor driving the improved cropland WUE over the past two decades. These insights have important implications for developing adaptive water management strategies to enhance agricultural climate resilience in Northeast China and similar regions worldwide. Full article

This study presents a risk assessment of asphaltene–resin–paraffin deposition (ARPD) in the producing formations of the XIII reservoir unit of the Uzen oil field at a late stage of development. The crude oil is characterized by an extremely high paraffin (wax) content of up to 29 wt.%. Long-term operation of the reservoir pressure maintenance (RPM) system with cold water injection has resulted in significant reservoir cooling, with temperatures declining from the initial 60–65 °C to 20–30 °C in zones of intensive waterflooding. To refine the critical phase transition temperatures of paraffin components, a dynamic laboratory approach was applied using a Wax Flow Loop system, which simulates wax deposition processes under flowing conditions. The results indicate that the wax appearance temperature (WAT) ranges from 41.0 to 44.0 °C, significantly exceeding the current bottomhole temperatures in the cooled zones of the reservoir. Intensive bulk crystallization of paraffins occurs within the temperature interval of 33.5–35.0 °C, while loss of oil flowability is observed at 25–34 °C, corresponding to the gelation and structural network formation of wax crystals under reduced thermal conditions. The obtained results confirm the inevitability of bulk oil structuring and solid wax phase precipitation directly within the reservoir porous medium. This process leads to blockage of low-permeability interlayers, deterioration of filtration properties, and a reduction in the displacement efficiency factor by 20–35%. Under the current thermal regime, ARPD should therefore be considered not merely as an operational flow assurance issue, but as a systemic factor limiting reservoir development efficiency. The research results substantiate the need to transition from reactive ARPD removal methods to proactive management of the thermal regime of the reservoir and wells, as well as to the differentiated application of thermal and chemical treatment methods. Full article

The urgent global need for sustainable infrastructure drives the demand for high-value buildings and waste removal. This paper studies the feasibility of using recycled foam concrete aggregate (FCA) as a substitute for natural coarse aggregate (NCA) in concrete and studies its impact on rheology, mechanical degradation, shear resistance, and the full-range replacement ratio (0–100). The experimental results show that the monotonic change in the workability of fresh concrete determines the lubrication threshold at 60% replacement, which is driven by the volume proportion effect. Beyond this value, capillary suction dominates, and the viscosity rises rapidly. From a mechanical perspective, the porous structure of FCA is conducive to “internal curing” so that moisture is released from the drying interface, but it also becomes a source of defects that change the fault topology. Specifically, the critical transition of the shear failure mode shifts from the debonding of the interface to the crushing of the cross-particle aggregate. At this time, the shear capacity decreases substantially, experiencing a reduction of 71.8% when completely replaced. There is a strong correlation between ultrasonic pulse velocity (UPV), rebound number, and compressive strength, and a multivariate nonlinear regression model (R² > 0.85) with non-destructive strength prediction is ultimately obtained. Based on the balance between mechanical capacity and resource cyclability, an optimal alternative zone of 20% to 40% is proposed. This work not only provides a mechanism for multi-scale coupling between pore structure and structural properties but also provides a data-driven method for the safety assessment of lightweight recycled aggregate concrete (RAC). Full article

The Dongchuan District in Kunming City is located in the transition zone between the Yunnan–Guizhou Plateau and the Sichuan Basin. As a region with a copper mining history of over 2000 years, the district has experienced frequent landslides that pose serious threats to human lives, property, and ecological sustainability. Therefore, it is essential to compile a comprehensive landslide inventory and analyze the relationships between landslide spatial distribution and influencing factors for geological hazard prevention. High-resolution remote sensing imagery was interpreted to establish a landslide inventory, based on which the spatial distribution and geometric characteristics of landslides were systematically analyzed. The results show that a total of 1623 landslides were identified, with a total area of 10.36 km². Landslides predominantly occur at elevations of 1000–2000 m, on slopes of 20–45°, with aspects of 255–285°, and relief between 150 and 400 m, in areas with annual rainfall below 825 mm, within 1000 m of rivers and 3000 m of fault lines, and 1000–5000 m of mines. Four landslide clusters were delineated along the Xiao River Fault, highlighting the significant influence of the fault on the spatial distribution of landslides. Most landslides are longitudinal in planform, with travel distances (L) of 50–450 m and heights (H) from 25 to 350 m, both exhibiting allometric scaling with volume. The mean H/L ratio is 0.56 (corresponding to a mean reach angle of 29°), significantly higher than that in Baoshan City (21°). The results provide insights into landslide initiation mechanisms and spatial distribution patterns on the northern margin of the Yunnan–Guizhou Plateau, offering valuable data for landslide hazard assessment and sustainable regional development. Full article

To identify the sources and driving mechanisms of nitrate contamination in pore water around Nansi Lake, 54 pore water samples were analyzed via hydrogeochemical analysis, Gibbs diagrams, ionic ratios, and principal component analysis (PCA). The pore water is predominantly slightly alkaline, with dominant cations Ca²⁺ and Na⁺, and anions HCO₃⁻ and SO₄²⁻. Nitrate-nitrogen (NO₃⁻-N) concentrations range from 0.82 to 54.31 mg·L⁻¹, with a coefficient of variation of 1.41 and an exceedance rate of 18.52%, indicating significant external inputs. A positive correlation between NO₂⁻ and NO₃⁻ suggests denitrification in some areas. Nitrate concentrations exhibit distinct spatial heterogeneity: high concentrations occur in agricultural/aquaculture lakeside plains and urban areas, low concentrations near coal mining subsidence zones, and transitional zones showing outward diffusion. Nitrate sources are predominantly anthropogenic. High Cl⁻ and low NO₃⁻/Cl⁻ ratios indicate domestic and aquaculture wastewater infiltration, whereas low Cl⁻ and high NO₃⁻/Cl⁻ ratios indicate agricultural fertilizer input. Industrial and natural sources are minor. PCA identified three controlling factors (cumulative variance 69.81%): coal mining and industrial/domestic pollution (39.82%), carbonate rock weathering (19.44%), and agricultural activities (10.55%). Health risk assessment shows no significant risk for adults (hazard quotient (HQ) < 1), but children face localized risks at nine sites (HQs of 1.25–2.26) in intensive farming, urban, and transitional zones. Excessive fertilizer application and sewage leakage are the primary causes, posing methemoglobinemia risks to infants. This study provides a scientific basis for nitrate pollution control and sustainable water management in the Nansi Lake Basin and offers methodological insights for similar lacustrine plain regions. Full article