Search Results (107)

Organic amendments can alter soil structure, root development, and carbon cycling, yet their coordinated effects remain unclear. Based on a long-term field microplot experiment established in 2009, four amendment systems with equivalent annual N, P, and K inputs but differing in amendment properties and nominal annual organic-material C inputs were compared: maize straw with NPK (CS), pig manure compost with NPK (PMC), biochar with NPK (BIO), and biochar-based fertilizer (BF). After 15 years, dry-sieved aggregate distribution, CT-resolved air-filled pores (>30 μm), peanut root morphology, and easily oxidizable organic carbon (EOC), microbial biomass carbon (MBC), and dissolved organic carbon (DOC) were determined. PMC had the highest CT-resolved total and connected porosities (19.01% and 10.86%), a greater proportion of small macroaggregates, and the largest root surface area. CS produced a greater proportion and mean size of large dry-sieved aggregates and the highest bulk-soil MBC content. BIO and BF showed lower CT-resolved total porosity but greater isolated porosity, anisotropy, mean pore diameter, and pore fractal dimension (collectively termed CT-resolved macropore heterogeneity); these treatments were also associated with greater root volume or length and increased EOC and DOC contents in small macroaggregate- and microaggregate-sized fractions. Root length correlated more strongly with macropore heterogeneity than with total porosity. Because measurements were obtained once from 12 microplots, these relationships and SEM results represent exploratory associations rather than causal pathways. Overall, traditional amendments were associated with aggregation or macropore connectivity, whereas carbonized amendments were associated with greater macropore heterogeneity. BF had the highest percentage of EOC in TOC (52.45%), indicating a greater relative contribution of labile carbon, not increased stable carbon stock. Full article

Frozen soil on alpine slopes is influenced by inclination and aspect-induced differential solar radiation effects, resulting in non-uniform temperature fields and inclined layered ice lenses that enhance anisotropy and degrade mechanical properties. This study investigates the deformation and strength responses of frozen soil under different temperature-gradient magnitudes and orientations and ice-lens conditions. A stress–strain constitutive model incorporating the magnitude and orientation of the temperature gradient is established. In addition, an equal-scale discrete element model based on the parallel-bond contact model is developed and calibrated against the laboratory results. The numerical specimen is divided into 13 layers, and temperature-dependent interparticle bond properties are assigned layer by layer to reproduce the prescribed magnitude and orientation of the temperature gradient. Results show that the orientation of the temperature gradient significantly alters the mechanical response and failure mode. As the inclination angle increases, the failure mode transitions from compressive dilatancy to combined dilatancy–shear failure and ultimately to shear-dominated failure. At −10 °C, increasing the inclination angle from 0° to 30° reduces the compressive strength by 44.48%. The elastic modulus also decreases with increasing inclination, with a maximum inclination-induced difference of 111.98 kPa. Moreover, the presence of an ice lens further reduces specimen stiffness, and the elastic-modulus difference between ice-lens-bearing and ice-lens-free specimens increases from 5.57 kPa at −1 °C to 75.72 kPa at −10 °C. The DEM results show that particles at the top and bottom of the specimen primarily undergo vertical displacement, whereas particles in the middle region exhibit dominant horizontal displacement, forming an X-shaped shear band. The inclined temperature gradient produces a heterogeneous distribution of interparticle bond strength within each horizontal layer. As inclination increases, the shear band evolves from symmetric to asymmetric; particle displacements on the side toward which the temperature gradient points are larger than those on the opposite side, revealing the microscopic origins of macroscopic mechanical behavior. Full article

The reciprocating cutterbar is evolving from a conventional harvesting mechanism into an intelligent end-effector for crop harvesting, mechanical weeding, and selective cutting. However, plant anisotropy, moisture-dependent fracture, root-soil constraints, vibration, and wear still hinder low-energy cutting, long service life, and robust control. This review integrates harvesting and mechanical weeding within a unified analysis of reciprocating cutterbar technologies. It first links plant tissue structure and dynamic fracture to blade penetration, fiber stretching, crack propagation, and energy dissipation. It then examines how cutting speed, sliding-cut angle, blade clearance, and root-soil anchorage jointly affect performance. Advanced testing, response surface methodology, discrete element method, finite element method, and multiphysics simulations are compared for failure analysis, parameter optimization, and contact modeling. The review further assesses bionic blade design, surface strengthening, composite coatings, novel transmissions, multisource perception, and adaptive control. Key barriers include inconsistent plant-mechanics datasets, computationally intensive models, limited field robustness, and conflicts among performance objectives. We therefore identify digital twins, modular electric cutterbars, and closed-loop control as priorities for translating mechanistic insight into reliable field performance. Full article

Accurate estimation of soil surface moisture (SSM) is essential for various applications, including hydrological modeling, precision agriculture, and drought monitoring. With advancements in SAR data acquisition and modeling techniques, accurate retrieval of SSM has become increasingly feasible. The sensitivity of C-band (5.36 GHz) SAR data to the orientation of surface roughness with respect to the sensor look angle significantly influences surface soil moisture estimation results. Hence, to address this research gap, a modified eigen-space transformation was employed to obtain optimized surface roughness estimates, known as synthetic surface roughness (SSR). The results of the proposed SSR showed adequate statistical significance with the field-scale surface roughness values (r = 0.77, RMSE = 0.08) for all orientation angles, compared with the cross-polarization ratio (CPR) (r = 0.70, RMSE = 0.35) and Inverse of Anisotropy (A_I) (r = 0.59, RMSE = 0.49) measures. The modified Dubois model was inverted to retrieve the dielectric constant (ε_SSR) using SSR as a roughness proxy, demonstrating reliable performance for surface roughness conditions up to 4 cm and in situ dielectric constant values up to 8.5 (~29% volumetric soil moisture). However, exceeding this threshold leads to an underestimation of ε_SSR (Bias= −0.43), and hence a new framework, the optimized dielectric model (ε_ODM), was introduced using a piecewise-constrained angular projection correction. The volumetric moisture content (mv_ODM) retrieved from ε_ODM was promising (r = 0.86, RMSE = 0.04, Bias = 0.02) across a wide range of soil moisture conditions when compared with widely adopted backscattering models, namely Mod. Dubois, Calibrated IEM, Oh, and Mod. Oh. Full article

Biomimetic snake-scale interfaces exhibit pronounced shear anisotropy, demonstrating promising application potential in the optimal design of soil–structure interfaces. To elucidate the underlying mechanisms of this anisotropy, this study employs the discrete element method (DEM) to develop a ring shear model of the glass bead–biomimetic snake-scale interface. Based on the simulation results, the shear response and its micromechanical evolution under constant normal stress are analyzed, and the effect of normalized scale height H/d and its underlying mechanism are discussed. The results indicate that the biomimetic snake-scale interface exhibits significant directional shear differences, with cranial shearing yielding a higher peak shear stress than caudal shearing. Moreover, cranial shearing forms a thicker shear band, where particles adjacent to the interface are more prone to interlocking at the steep slopes of the scales, thereby establishing a stronger force chain structure. Furthermore, the scale height exerts a nonlinear influence on the interfacial strength. For the particle-size and scale-length conditions considered in this study, cranial shear strength exhibits an apparent threshold response with increasing H/d, which is associated with particle climbing and trapping mechanisms, whereas caudal shear strength increases gradually. These findings may provide a useful reference for the design and potential engineering application of biomimetic snake-scale interfaces. Full article

During wet–dry cycles, cracks in expansive soil evolve continuously, resulting in remarkable changes in the structural and textural characteristics of the soil mass. In this study, wet–dry cycle tests combined with CT scanning were carried out on undisturbed expansive soil collected from Hefei, and the gray-level co-occurrence matrix (GLCM) method was introduced to quantitatively extract the internal texture features of cracks from sequential CT images. Four GLCM parameters—angular second moment (ASM), contrast (CON), entropy (ENT), and correlation (COR)—were extracted at four directions (0°, 45°, 90°, and 135°) to investigate the texture evolution and directional anisotropy. The results indicate that cracks first initiate at weak positions near the top of the specimen and then extend downward, gradually developing into strip-shaped fractures and ultimately forming a three-dimensional crack network. With progressive crack development, the average gray value of CT images decreases from 198.06 to 137.38, and the distribution characteristics of gray values change significantly. To further quantify the spatial heterogeneity and directional anisotropy of the crack network, four GLCM texture parameters were extracted. Quantitatively, ENT and CON increase sharply with the number of wet–dry cycles: after the 5th cycle, ENT rises by 231–249% and CON by 317–335% across the four directions. Conversely, ASM and COR gradually decrease, with ASM declining by 25–29% and COR by 68–74%. All four parameters follow a logistic function with respect to the number of cycles (R² > 0.99). Furthermore, CON and ENT exhibit statistically significant directional differences, enabling the identification of dominant crack development directions, whereas ASM shows a consistent but non-significant directional trend and COR is insensitive to directional variations. These findings demonstrate that GLCM parameters possess good applicability for the quantitative characterization of internal crack texture in expansive soil. This study provides an effective method for investigating crack evolution and offers a new perspective for CT image analysis of rock and soil mass. Full article

The mechanical response of unstabilized rammed earth (URE) depends on a chain of factors spanning from soil composition to compaction conditions and specimen geometry and manufacturing conditions. This paper proposes a multiscale experimental framework for the physical and mechanical characterization of URE, structured around three hierarchical scales—soil, fabric and specimen—and demonstrates it on a single soil sample used consistently across more than a decade of experimental campaigns. At the soil scale, mineralogical composition, particle size distribution, Atterberg limits and linear shrinkage are determined. At the fabric scale, Proctor compaction tests establish the optimum moisture content and maximum dry density, and cohesion tests quantify the tensile cohesion of the material. At the specimen scale, monotonic and cyclic uniaxial compression tests reveal that compressive strength is essentially isotropic with respect to loading direction, while stiffness exhibits a pronounced anisotropy, with an anisotropy coefficient of 2.6. A Proctor-based specimen manufacturing procedure is used to reduce the coefficient of variation of compressive strength from 11.8% to 1.8%, demonstrating the critical role of compaction control in result reproducibility. Diagonal compression tests yield a shear strength of approximately 10% of the compressive strength, consistent with the tensile-to-compressive strength ratio commonly reported for URE. The proposed framework highlights the limitations of single-parameter characterization and provides methodological guidance applicable from soil evaluation to full mechanical characterization of URE. Full article

Metal accumulation in cacao (Theobroma cacao L.) cultivation represents an important agronomic and food-safety concern, particularly in acidic tropical soils where cadmium (Cd) and other trace metals can become bioavailable and translocate to plant tissues. Green magnetic nanomaterials offer a potential strategy for reducing metal mobility in agricultural substrates, but their performance depends on surface chemistry, dose, and plant genotype. In this study, we synthesized and evaluated MCRES, defined here as a maghemite–Citrus reticulata extract system, a biofunctionalized γ-Fe₂O₃-based nanosystem prepared by coupling iron oxide nanoparticles (NPs) with a 3% (w/v) Citrus reticulata peel extract. The objective was to determine whether citrus-mediated biofunctionalization could produce a scalable magnetic nanoamendment capable of modifying Cd and naturally occurring Ni partitioning in cacao seedlings. MCRES was recovered magnetically and dried, yielding 8.44 g of product from 10 g of precursor. Rietveld analysis performed in X ray diffractograms confirmed phase-pure cubic γ-Fe₂O₃ with a lattice parameter of 0.8332 nm, a crystallite size of 11.3(1) nm, and satisfactory refinement quality (χ² ≈ 1.34). Transmission electron microscope images showed quasi-spherical NPs with a log-normal size distribution centered at 7.5 nm. Magnetic measurements showed superparamagnetic-like behavior at 300 K, high saturation magnetization values of 62 emu g⁻¹ at 300 K and 71 emu g⁻¹ at 5 K, and elevated effective anisotropy values obtained from the Law of Approach to Saturation fitting. MCRES was applied at 0, 1, 2, 4, and 6 g pot⁻¹ to cacao seedlings containing Cd-amended Ultisol with naturally occurring Ni. Plant responses were genotype and dose dependent: TSH-1188 genotype showed limited dose sensitivity for most biometric variables, whereas ICS-95 genotype showed significant dose effects, with maximum growth at the 2 g pot⁻¹ treatment. Metal-partitioning results indicated that Cd remained comparatively mobile toward shoots, whereas Ni was preferentially retained in roots. In TSH-1188 genotype, the Ni translocation factor decreased from 3.07 in the control to 0.85–1.00 at higher MCRES doses. Compared with previous work on non-biofunctionalized nanomaghemite, these results suggest that citrus-mediated biofunctionalization produces a distinct Cd/Ni partitioning response. Overall, MCRES is recommended as a promising nursery-scale green nanoamendment for reducing metal mobility in cacao cultivation, but its agronomic use should be optimized according to genotype and dose. Future work should include side-by-side comparisons with unfunctionalized γ-Fe₂O₃, Citrus reticulata extract alone, and non-contaminated controls under field conditions to validate its long-term effectiveness and environmental safety. Full article

Accurate prediction of natural gas dispersion from buried pipelines is critical for risk assessment and emergency response. However, conventional numerical simulations often simplify soil as a homogeneous isotropic porous medium, which deviates significantly from real-world conditions characterized by stratification, anisotropy, and spatial heterogeneity. This study systematically investigates the effects of these non-ideal soil characteristics on methane diffusion behavior using computational fluid dynamics (CFD). Four distinct soil models—a baseline homogeneous model, a layered model, an anisotropic model, and a spatially heterogeneous model—were constructed and compared under identical leakage scenarios. Key risk indicators, including First Danger Time (FDT), Farthest Danger Range (FDR), Ground Danger Range (GDR), and leakage mass flow rate, were quantitatively evaluated. Results indicate that soil layering enhances vertical migration and expands horizontal hazard ranges, reducing FDT by approximately 8%. Anisotropy introduces a pronounced directional dependence in gas migration, with horizontal-preferred permeability leading to severe underestimation of lateral risk by homogeneous assumptions. The spatially heterogeneous model exhibits reduced hazard ranges compared to the homogeneous case but accelerates early breakthrough. Comprehensive evaluation reveals that the homogeneous model systematically underestimates lateral diffusion distances and delays alarm times. This study provides a quantitative basis for selecting appropriate soil modeling strategies, emphasizing that incorporating soil heterogeneity is essential for reliable safety assessments of buried gas pipelines. Full article

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

Defining the near-surface signal reflecting the deep sub-surface leakage is a critical challenge in the risk assessment of geologic carbon storage (GCS) projects, often exacerbated by decoupled deep-to-shallow modeling. This study quantifies the mass distribution and phase evolution of leaked CO₂ through deep reservoir-caprocks, intermediate aquifer, and near-surface soil, thereby showing the sub-surface retention characteristics and the detectability of near-surface signals. A geological model from the deep reservoir to the soil layer was constructed to simulate CO₂ leakage through the caprock and migration into overlying strata in 1000 years. Using the simulator of GPSFLOW, this study evaluates the evolution of fluid phases and the mass distribution during the injection for 100 years and the post-injection periods. The results indicate that (1) at the moment the injection ceases, 87.43–99.06% of the CO₂ remaining within the system is retained within the reservoirs, with less than 8.42% reaching the intermediate aquifer. Remarkably, although the CO₂ ultimately reaching the near-surface soil is less than 0.00073% of the total mass retained within the system, this mass accumulation translates to a concentration anomaly with a signal-to-noise ratio of 368 relative to the background baseline. (2) Sensitivity analysis reveals that the injection rate affects the timing of fluid transport—a tenfold increase in injection rate (from 3.17 to 31.7 kg/s) accelerates the upward movement of CO₂, advancing its arrival at the near-surface by 15 years without changing the overall mass partitioning. The permeability anisotropy ratio affects CO₂ migration and phase distribution—decreasing the vertical to horizontal permeability ratio (1, 0.5, 0.25, 0.125) reduces connectivity, which delays the upward transfer and increases the amount of the aqueous CO₂. However, specifically in the soil layer, the aqueous CO₂ accumulation reveals a non-monotonic trend that peaks at an intermediate ratio of 0.25. (3) CO₂ shows a cascading distribution across formations where reservoirs provide the primary storage, and the intermediate aquifer reduces the mass available for near-surface accumulation. This attenuation effect significantly reduces the CO₂ mass that reaches the soil layer, thereby controlling the strength and duration of near-surface environmental signals. This work offers a theoretical reference for formulating near-surface monitoring strategies for CO₂ leakage in GCS. Full article

The long-term stability of embankments is directly influenced by the stress paths associated with river water level fluctuations. To investigate the anisotropic characteristics of slope soil in embankments under such drainage-induced gradual loading conditions, a series of drained directional shear tests was conducted on slope soil to investigate the coupled effects of the principal stress direction angle α and the intermediate principal stress coefficient b on its strength, deformation, and non-coaxial characteristics. Results showed that radial strain exhibited minimal sensitivity to variations in the principal stress direction angle α at the constant principal stress coefficient b. The circumferential and axial strain directions demonstrated symmetry. Specimens initially contracted then dilated during shearing. Octahedral shear strain anisotropy was more significant at b = 0.5 and 1 than at b = 0. For a constant α, the normalized strength at b = 0.5 exceeded that at b = 0 and 1. Strength showed significant anisotropy across angles α at a constant b. Specimens exhibited significant non-coaxial behavior under axial-torsional shear loading. This study offers theoretical insight into embankment slope behavior under anisotropic stress paths. Full article

Soil pore architecture and hydraulic functioning strongly regulate water flow and retention. However, despite the growing application of X-ray computed tomography (X-ray CT) in soil science, its application in characterizing the pore system and hydraulic functioning of native forest soils converted to sugarcane production systems in northeast Brazil is still poorly known. This study therefore quantified the soil structure, pore system, and hydraulic functioning of a native forest (NF) and an adjacent sugarcane field receiving vinasse and managed without intercropping (sole sugarcane (SG)) and with Brachiaria ruziziensis intercropping (SG + Bra intercrop) in northeastern Brazil, using conventional soil physical measurements and X-ray CT, in three soil layers (0–10, 10–20, and 20–40 cm). Soil physical and hydraulic properties, as well as soil water retention, were quantified. The native forest soil exhibited a uniformly sandy texture across all depths, whereas sugarcane systems ranged from loam to sandy textures in surface layers due to long-term management. Soil organic matter and total nitrogen in the 0–10 cm layer were approximately 75 and 65% higher, respectively, in sole Sole SG and SG + Bra intercrop than in NF. Soil bulk density increased with depth under sugarcane, reaching values about 10%–13% higher than NF in the 20–40 cm layer. Saturated hydraulic conductivity in the surface layer was higher in the NF, approximately five to nine times greater than in sole SG and SG + Bra intercrop, respectively. Conventional water retention analysis showed that sole SG and SG + Bra intercrop had greater total porosity (0.49–0.55 m³ m⁻³), microporosity (0.26–0.36 m³ m⁻³), field capacity (0.19–0.33 m³ m⁻³), and plant available water (0.09–0.15 m³ m⁻³) in the upper 20 cm compared with the NF (≤0.10 m³ m⁻³ available water). In contrast, X-ray CT revealed higher macroporosity (0.20–0.23 mm³ mm⁻³) and pore connectivity in the NF across all depths, with predominantly complex, inclined to near-horizontal pores and low anisotropy. Intercropping sugarcane with Brachiaria did not significantly alter (p > 0.05) bulk density, hydraulic conductivity, or CT-derived pore connectivity relative to sole sugarcane. The degree of anisotropy and fractal dimension derived from X-ray CT were significantly correlated (p < 0.05) with conventionally measured hydraulic properties. The X-ray computed tomography proved effective in linking pore-scale architecture to soil hydraulic functioning, providing insights beyond conventional measurements. The short-term inclusion of Brachiaria as a cover crop at 10 kg seed ha⁻¹ did not result in significant improvements in soil pore structure, indicating that longer-term adoption and/or higher planting densities may be required to induce measurable changes in pore system architecture and soil hydraulic functioning. Full article

Topography regulates vegetation functioning by controlling water redistribution, microclimate, and solar exposure. In Mediterranean ecosystems, where water availability constitutes a fundamental limiting factor, vegetation functioning is also influenced by environmental drivers such as temperature, climatic seasonality, drought recurrence, and soil properties that interact with terrain heterogeneity. Understanding how these elements operate at the micro-scale is essential for interpreting the spatial variability of photosynthetic vigor and canopy water condition. This study evaluates the relationships between the topographic metrics Topographic Position Index (TPI), Terrain Ruggedness Index (TRI), and Diurnal Anisotropic Heat Index (DAH) and two spectral proxies of vegetation condition, the Normalized Difference Vegetation Index (NDVI) and the Normalized Difference Moisture Index (NDMI), in Los Nogales Nature Sanctuary (central Chile). Multitemporal Sentinel-2 time series (2017–2025) were analyzed using Generalized Additive Models (GAMs) with Gaussian distribution and cubic splines to detect non-linear topographic responses. All topographic predictors were statistically significant (p < 0.001). NDVI and NDMI values were higher in concave and less rugged areas, decreasing toward convex and thermally exposed slopes. NDMI exhibited greater sensitivity to topographic position and thermal anisotropy, indicating the strong dependence of vegetation water condition on topographically driven water redistribution. These results highlight the role of terrain in modulating vegetation vigor and moisture in Mediterranean ecosystems. Full article

This technical note presents a quantitative image-based framework for evaluating the packing and compressibility of granular soils, specifically applied to building foundation design in civil infrastructure projects. The Sedimaging system replicates hydraulic sedimentation in a controlled column, equipped with a high-resolution camera, to visualize particle orientation after deposition. Grayscale images of the settled bed are analyzed using Haar Wavelet Transform (HWT) decomposition to quantify directional intensity gradients. A new descriptor, termed the sediment index (B), is defined as the ratio of vertical to horizontal wavelet energy at the dominant scale, representing the preferential alignment and anisotropy of particles during sedimentation. Experimental investigations were conducted on fifteen granular materials that include natural sands, tailings, glass beads and rice grains with different shapes. The results demonstrate strong correlations between B and both microscopic shape ratios (d₁/d₂ and d₁/d₃) and macroscopic properties. Linear relationships predict the limiting void ratios (e_max, e_min) with mean absolute differences of 0.04 and 0.03, respectively. A power-law function relates B to the compression index (C_c) with an average deviation of 0.02. These findings confirm that the sediment index effectively captures the morphological influence of particle shape on soil packing and compressibility. Compared with conventional physical testing, the Sedimaging-based approach offers a rapid, non-destructive, and high-throughput solution for estimating soil packing and compressibility of cohesionless, sand-sized granular soils directly from post-settlement imagery, making it particularly valuable for preliminary site assessments, geotechnical screening, and intelligent monitoring of granular materials in building foundation design and other infrastructure applications, such as earth–rock dams. Full article