Search Results (5,532)

To address the safety assessment challenges associated with repeated and continuous excavation-induced vibrations in high-rise residential projects founded on hard rock, this study proposes a novel multi-scale dual-control evaluation framework bridging macroscopic ground peak particle velocity (PPV) with microscopic structural principal tensile stress. A geotechnical–structural decoupling approach was adopted. First, a two-dimensional dynamic finite element model of the ground was developed to simulate the propagation and attenuation characteristics of elastic waves under continuous excavation impact loading. Subsequently, the acceleration time histories extracted from the soil–structure interface were applied as base excitations in a three-dimensional structural finite element model to systematically investigate the dynamic response characteristics. The scientific novelty of this research lies in quantitatively decoupling the dynamic sensitivities between primary load-bearing shear walls and secondary non-load-bearing walls, thereby overcoming the inherent blind spots of conventional PPV-only macroscopic assessments. The results indicate that in hard-rock foundations, vibration energy is dominated by vertical attenuation characteristics. Compared with primary load-bearing structures mainly governed by static self-weight effects, secondary non-load-bearing components with lower stiffness exhibit significantly higher dynamic sensitivity and localized vulnerability to continuous impact loading. Parametric analysis further reveals that while the number of operating equipment shows a linear positive correlation with vibration amplitude, the impact frequency dictates the system’s dynamic response. Notably, when the excitation frequency approaches the dynamically sensitive frequency range of the foundation system, a pronounced divergence in response characteristics is observed—manifested as a sharp increase in local structural stress despite a reduction in ground macroscopic vibration intensity. These findings provide a rigorous theoretical foundation and a refined methodology for vibration impact assessment in urban hard-rock foundation construction. Full article

Three-dimensional numerical investigations into the synergistic mechanism of composite pile retaining systems consisting of large-diameter bored cast-in-place piles and small-diameter micro-grouted steel pipe piles remain limited. To address this gap, a refined three-dimensional finite element model was established using ABAQUS based on the Hutan Park Station excavation project of Dalian Metro Line 5. Five design cases were analyzed by varying pile diameter, pile spacing, and the presence or absence of micro piles. The main findings are as follows: (1) The maximum horizontal soil displacement in all cases remained below 8 mm, indicating satisfactory excavation stability. (2) The inclusion of micro piles promoted stress redistribution within the inter-pile soil and was associated with a more pronounced soil arching tendency, as indicated by the displacement contour patterns. (3) Based on the comparison between Case 3 and Case 5, where the spacing between bored cast-in-place piles increased from 2.0 m to 3.0 m while maintaining the composite support configuration, the maximum horizontal displacement and maximum bending moment decreased by approximately 12% and 9%, respectively. The inserted micro-grouted steel pipe piles participated in lateral load transfer, enhanced stress redistribution, and reduced local stress concentrations acting on the primary bored piles. Under the investigated geological and support conditions, the numerical results suggest that the introduction of micro steel pipe piles may improve deformation control and load-sharing performance in composite pile-supported excavations. The proposed support configuration shows potential for reducing the number of large-diameter bored piles while maintaining acceptable excavation performance and overall support stability. Full article

With the growing potential correlation between chromium (Cr), molybdenum (Mo), and human health, public attention to these elements has increased markedly. In Beijing, the capital of China, research on the concentration levels of Cr and Mo is urgently needed. In recent years, soil geochemical surveys have been conducted in the Beijing region, with a scale of 1:100,000 in mountainous areas (yielding 8575 data points) and 1:50,000 in plain areas (yielding 29,551 data points). These surveys provide a robust dataset for elucidating the concentrations and distribution patterns of soil elements. In surface soil samples from Beijing (n = 38,126), the mean concentrations of Cr and Mo were 55.7 µg/g and 0.67 µg/g, respectively. Recently, scholars have proposed a 19-level fixed-value method for Mo concentrations. Based on this, the 19-level fixed-value method for Cr concentrations is proposed to facilitate cross-element comparisons. This method classifies the elemental concentrations from its detection limit to its cut-off grade of mineralization into 19 levels on 18 fixed values. With this method, the concentration levels of Cr and Mo in Beijing soils are both at the fifth level on their mean values, which belong to the background level. To compare the Cr and Mo concentrations in soils with other capital cities, statistical parameters of Cr from 20 capital cities and Mo from 11 capital cities were collected. The results show that the mean Cr concentration levels in the 20 cities range from 2 to 10, while the mean Mo concentration levels in the 11 cities range from 5 to 10. In these capital cities, the Cr level of Beijing is at the middle level, and the Mo level is at the low level, which indicates the cross-element comparison on the 19-level fixed-value method. Full article

Surface dust samples were collected from bus stops and parking lots in different functional areas of Binzhou City, Shandong Province, China. This study investigated the contamination characteristics, source apportionment, and potential ecological and health risks of potentially toxic elements (PTEs) in these dust samples. Eight target PTEs, including As, Zn, Pb, Cu, Cd, Cr, Ni, and Mn, were quantitatively analyzed. The results revealed distinct concentration differences in these elements between bus stop dust and parking lot dust. Several PTEs exceeded the corresponding local soil background values, predominantly Zn, Pb, Cu, Cd and Cr. Principal component analysis (PCA) indicated that Zn, Pb, Cu, Cr, Ni, and Mn in bus stop dust were mainly sourced from traffic emissions, whereas As and Cd primarily originated from atmospheric deposition. For parking lot dust, Zn, Pb, Cu, Cd, Cr, and Mn were predominantly attributed to traffic sources, while As and Ni were mainly derived from natural background sources. The geo-accumulation index (I_geo) demonstrated that As, Cr, Ni, and Mn had negligible environmental impact, Pb, Cu, and Cd induced slight pollution, and Zn resulted in moderate pollution. Except for Cd, the average individual potential ecological risk index ($E_r^i$) values for all elements were below 40, suggesting a low ecological risk. Cd posed a moderate ecological hazard, whereas the comprehensive ecological risk index ($E_r^i$) values of all analyzed elements were at an extremely low level. The hazard index (HI) values via different exposure pathways and for all PTEs in both bus stops and parking lots were lower than 1, indicating no significant non-carcinogenic health risk. The carcinogenic risk ranking of elements was Cr > Cd > Ni > As, and their carcinogenic risk values (CR) via inhalation exposure were below 1 × 10⁻⁶, indicating no carcinogenic risk. This study provides a scientific basis for the environmental quality control and risk management of surface dust in urban bus stops and parking lots. Full article

Spaceborne imaging spectroscopy has created new opportunities for monitoring soil properties at regional scales. Its use for predicting soil heavy metal concentrations in mountainous environments, however, remains insufficiently tested, especially when EMIT hyperspectral data are used. In this study, EMIT Level-2A surface reflectance data were integrated with DEM-derived terrain variables to estimate soil arsenic (As), copper (Cu), and zinc (Zn) concentrations in Renhuai, Guizhou Province, Southwest China. Only soil samples falling within valid EMIT coverage were used for element-specific modeling, resulting in 139 samples for As, 136 for Cu, and 130 for Zn. To reduce redundancy among predictors, EMIT spectral variables and terrain factors were screened before model construction. Random forest and XGBoost models were then tested using repeated spatial cross-validation. The best-performing model for As combined EMIT predictors with elevation and achieved a validation R² of 0.460. Model performance was considerably weaker for Cu, with a validation R² of 0.188. For Zn, the model failed to outperform the mean-based benchmark, producing a negative validation R² of −0.028. The spatial prediction maps and residual patterns suggested that the EMIT-based prediction showed moderate potential for As, limited predictive value for Cu, and exploratory rather than reliable mapping capability for Zn under the current sample and predictor conditions. Full article

Aiming at the problem that strip surcharge in coastal soft soil foundations causes lateral squeezing and endangers the safety of adjacent existing bridge pile foundations, the traditional Boussinesq elastic theory cannot reflect the true elastoplastic characteristics of the soil and tends to underestimate the actual horizontal additional stress. This paper establishes a two-dimensional plane strain finite element model and, based on the calibration of pure elastic theoretical solutions, carries out extensive comparative analyses under elastoplastic foundation conditions. Through Pearson correlation and random forest sensitivity analyses, it is clarified that the internal friction angle, load ratio, and normalized distance ratio are the core control variables affecting the redistribution of horizontal additional stress, thereby demonstrating the limitations of the influence of elastic modulus and cohesion. The study reveals the nonlinear amplification mechanism of horizontal stress transfer caused by the penetration of the deep plastic zone within the foundation, as well as the physical evolution law of the stress correction factor, which initially exhibits a Gaussian peak enhancement and subsequently decays exponentially with spatial distance. Based on these mechanisms, a combined prediction formula for the horizontal additional stress correction factor is proposed, achieving an R² = 0.903, and a safety evaluation chart for the correction factor is constructed to quantify high-risk areas. The results indicate that when the normalized distance ratio is greater than or equal to 4, the elastoplastic squeezing effect essentially dissipates. The proposed modification method effectively delineates the applicable boundary of the elastic solution and provides a theoretical basis for the bearing capacity calculation and safety control of passively loaded pile foundations in soft soil regions. Full article

Machine learning (ML) is increasingly applied to geochemical baseline estimation and anomaly detection in soils and sediments, yet the methodological conditions under which machine learning outperforms traditional approaches—and which preprocessing and validation decisions most consequentially determine that advantage—remain incompletely characterized across environmental and mineral exploration domains. A structured systematic scoping review of 146 records from the Web of Science Core Collection applied sequential filtering to yield 78 thematically eligible studies, from which 20 were prioritized through a composite index integrating age-adjusted citation impact, platform usage, and semantic relevance. Four cross-cutting findings emerge. First, performance gains in environmental applications were driven primarily by spatial model structure rather than algorithm selection: incorporating a spatial covariate derived from geographically weighted regression raised test-set explained variance from $R^2=0.80$ to $R^2=0.96$ for cadmium mobility prediction in a geochemically heterogeneous karst setting, a gain the source study supported with a held-out test set and a Monte Carlo analysis of sensitivity to data size. Second, isometric or centered log-ratio preprocessing was applied in the majority of mineral exploration studies (three of five classical and hybrid studies and four of five deep-learning studies) but in none of the seven environmental studies, representing a systematic methodological gap with direct consequences for covariate importance estimates under compositional closure. Third, Shapley additive explanations and accumulated local effects functioned as instruments of operational value, enabling element-specific anomaly threshold derivation, training sample diagnosis, and grid-cell anomaly type classification; this evidence demonstrates that the accuracy–interpretability trade-off commonly assumed in the machine learning literature is not fundamental in geochemical applications but contingent on algorithm selection. Fourth, 90% of the 20 synthesized studies (18 of 20 by study-area location—13 in China and five in Iran) were evaluated under within-domain validation designs, and the consistently high performance metrics reported should be interpreted as interpolation estimates rather than evidence of transferable predictive capability. Geographic diversification of training datasets and spatially explicit cross-regional validation are identified as structural prerequisites for regulatory-grade applicability. Full article

The growth of circular economy concepts has resulted in the need to develop methods for assessing circularity in geotechnical infrastructure systems. This paper proposes, for the first time, an initial framework for assessing circularity of geotechnical infrastructure systems and then uses it to assess the GeoBarrier System (GBS) as a case study. The framework considers five domains: water, energy, material, waste, and site quality. It was formulated based on a literature review, stakeholder requirements, and the case-specific characteristics of the GBS. Laboratory characterisation and numerical analyses were performed to assess the engineering performance of the system and support the circularity assessment. The results show that water circularity was the highest at 50.0%, meaning that half of the water in the system was effectively reused or recirculated. In contrast, energy circularity was absent due to the lack of renewable energy integration. Material and waste circularity performed at a moderate level, lower than water circularity, reflecting partial use of recycled materials and reuse of excavated soil. The site quality evaluation resulted in a score of 2.250, which, together with the other indicators, suggests an intermediate overall level of circularity performance. The assessment identified opportunities to improve circularity through greater on-site reuse of excavated waste, renewable energy integration, and improved site planning. The proposed framework is the first circularity/sustainability system specific to geotechnical infrastructure systems; therefore, apart from GBS, it is intended for potential applicability for evaluating circularity in other geotechnical systems. Full article

Aiming at severe soil secondary salinization, poor water retention and insufficient salt tolerance of conventional acrylic-based modifiers in arid and semi-arid regions of China, a poly(ethylene glycol) maleate citrate (PEGMC) crosslinking monomer was synthesized through esterification, and a dual covalent–hydrogen crosslinked P(PEGMC/AA) hydrogel was fabricated via free radical copolymerization with acrylic acid (AA). The hydrogel was characterized by NMR, FTIR, SEM, TGA and elemental mapping, while its binding mechanism with saline–alkali ions was elucidated through DFT calculations and molecular dynamics simulations. Its amelioration performance was evaluated through swelling, soil water retention, desalination and pot germination experiments. The hydrogel exhibited outstanding water absorbency, salt resistance and dry–wet cycling stability, with swelling ratios of 712 g/g in deionized water and 285 g/g in 0.9% NaCl solution, and remained 200 g/g after four dry–wet cycles. It enhanced soil water retention remarkably (over 93% after 72 h). At 0.30% dosage, soil salt content declined from 7.1 g/kg to 1.3 g/kg with desalination efficiency exceeding 80%, owing to porous physical adsorption and chemical chelation toward Na⁺, Ca²⁺ and Mg²⁺, with a binding energy of −136.936 kJ/mol. Pot tests revealed that crop germination rate rose from 19% (blank) to 75% under severe saline–alkali stress. Meanwhile, the hydrogel inhibited nutrient leaching and favored soil-water conservation. This work first incorporated PEGMC monomer into agricultural hydrogels to construct a stable dual crosslinked network, clarifying its synergistic mechanisms for salt fixation and water retention macroscopically and microscopically. It provides a promising functional material and theoretical basis for green, efficient in situ amelioration of dryland saline–alkali soil. Full article

Deep excavations in composite “soft upper-hard lower” strata present significant deformation control challenges due to strong stiffness contrasts. This study investigates the deformation characteristics of a deep metro foundation pit in Jinan under zoned excavation conditions. A three-dimensional finite element model was developed to simulate the staged excavation process, and the spatiotemporal evolution of diaphragm wall deflection and ground settlement was analyzed, with particular focus on the influence of soft soil thickness. The results show clear spatial variation, with maximum lateral wall displacements exhibiting a typical “bulging” profile along the longer sides of the pit. The normalized maximum wall displacement (δ_hm/H_e) ranges from 0.051% to 0.090%, while the ratio of maximum ground settlement to wall displacement is 0.35–0.57, indicating lower deformation levels compared to homogeneous soft soils. As the soft soil thickness increases, the wall displacement increases and the location of maximum displacement migrates downward and outward. Under the investigated conditions, a transition toward a “kick-out” deformation mode occurs when the soft soil thickness reaches the transition range identified in the parametric analysis. These findings provide a quantitative basis for deformation prediction and support design in composite strata. Full article

Foamed concrete has been used to construct lightweight embankments as a substitute for conventional fills, aiming to promote its engineering application in soft-soil regions. However, the dynamic response and safety mechanism of foamed concrete embankments during vehicle collision are not yet fully understood. In this paper, the safety performance of lightweight foamed concrete embankments under vehicle–guardrail collision and the optimal design of the guardrail foundation are investigated from the perspectives of lateral displacement and stress distribution. Through static uniaxial compression tests, the stress–strain curves, compressive strength, elastic modulus, and statistical variability of foamed concrete with six different mix proportions were obtained. On this basis, a coupled finite element model of the vehicle–guardrail–lightweight embankment system was established (the guardrail and its foundation were modeled using a linear elastic constitutive model, the embankment using a crushable foam model, and the vehicle using a 1.5 t passenger car model validated by full-scale crash tests). According to the passenger car impact conditions specified in current Chinese regulations (velocity 100 km/h, angle 20°), the peak lateral displacement and peak principal stress of the lightweight embankment were analyzed for four foundation base slab lengths (L₀, 1.1 L₀, 1.2 L₀, 1.3 L₀). The results show that increasing the base slab length effectively reduces lateral displacement and stress concentration. Increasing the length by 10–20% reduces the peak lateral displacement by up to 68%, and the peak principal stress remains far below the material strength. From the perspectives of structural stability and cost-effectiveness, a 10–20% increase in the base slab length is recommended. The ratio of the peak principal stress to the material strength can serve as a criterion for evaluating the safety margin and assessing the rationality of the foundation design. This study provides quantitative evidence for optimizing the guardrail foundation base slab length to enhance the collision safety of lightweight foamed concrete embankments, and the proposed design range offers a cost-effective reference for practical engineering applications in soft-soil regions. Full article

Selenium is a trace element of vital importance for ecosystem functioning and human health mainly due to its antioxidant and protective properties. Since both selenium deficiency and excess can have harmful effects on living organisms, monitoring its distribution in biological systems and the environment is of significant scientific and public health interest. This study systematically assessed selenium concentrations in biological (urine, serum, and hair) and environmental (soil and dandelion) samples in eastern Croatia. Selenium concentrations were determined using the inductively coupled plasma mass spectrometry method. In biological samples, median selenium concentrations were from 15.02 to 37.15 μg·L⁻¹ in urine, from 80.76 to 114.05 μg·L⁻¹ in serum, and from 0.21 to 0.46 µg·g⁻¹ in hair. In environmental samples, median selenium concentrations varied depending on location, ranging from 0.32 to 0.51 mg·kg⁻¹ in soil and from 6.55 to 84.41 µg·kg⁻¹ in dandelion. PCA was applied to identify overall patterns and groupings among biological and environmental samples, showing that dandelion samples from urban locations exhibited the highest selenium concentrations, indicating the influences of urban environmental conditions on selenium accumulation. Full article

Perennial alfalfa roots form a composite with the soil, contributing to intensified grassland degradation and reduced yields. Soil-loosening and root-cutting tools are effective in disrupting root–soil composites and reducing soil compaction. However, loosening and root-cutting operations commonly face challenges, such as high tillage resistance and disturbance. This study developed a simulation model of the alfalfa root–soil composite based on the coupled Finite Element Method (FEM) and Smoothed Particle Hydrodynamics (SPH) method when considering the biomechanical properties of roots. The validity of the model was verified using direct shear and cutting tests. The errors in both simulation and test results were less than 8%. Additionally, a vibration root-cutting shovel was designed. The factors of tillage speed, vibration frequency, amplitude, and direction were analyzed for their impact on tillage resistance and root shear displacement. Results indicated that the incorporation of vibration enhanced soil breaking and reduced root-cutting displacement. The optimal combination of parameters determined using the Response Surface Method (RSM) for minimizing tillage resistance and shear displacement were a tillage speed of 0.86 m·s⁻¹, vibration amplitude of 3.79 mm, vibration frequency of 45.05 Hz, and vibration parallel to the tillage direction. Field tests confirmed the effectiveness of the vibratory root-cutting shovel. The addition of vibration parallel to the tillage direction can reduce tillage resistance by 16.68% and penetration resistance by 26.80%. This study provides a methodology for modeling root–soil composite and improving the root-cutting shovel for grassland degradation restoration. Full article

The Ningxia Yellow River Urban Agglomeration, located in the ecologically fragile arid and semi-arid zone of the upper Yellow River, serves as a critical spatial carrier for maintaining the ecological security of the Yellow River Basin and supporting the regional economy and population agglomeration in Ningxia. Driven by rapid urbanization, intensified human–land conflicts have induced widespread ecological degradation and unbalanced water–soil resource allocation across the region. Based on land use data from 2010, 2015, 2020 and 2023, we applied the land use transition matrix, land use dynamic degree and standard deviational ellipse to characterize the spatiotemporal patterns of spatial expansion of the Ningxia Yellow River Urban Agglomeration over the past decade. The Patch-generating Land Use Simulation (PLUS) model was further employed to predict the land use demand and spatial distribution of the study area under diverse scenarios in 2035. The research results reveal three key findings. First, grassland, cropland and unused land constitute the dominant land use types across the study region, jointly occupying more than 90% of the total territorial area. Over the past decade, regional land use has undergone noticeable changes: grassland area has continuously declined, cropland and built-up land have sustained steady expansion, and water areas have experienced a mild reduction. Land use conversions mainly occur among grassland, cropland and built-up land. Second, driving factors vary substantially in their spatial contributions to the expansion of different land use types. The spatial growth of cropland and built-up land is comprehensively shaped by terrain conditions, economic development and transportation location superiority. In comparison, the distribution and dynamic changes in forestland, grassland and water areas are predominantly restricted by natural elements, including precipitation, temperature and soil characteristics. Third, multi-scenario simulation results verify that differentiated territorial spatial planning and regulatory policies profoundly affect the evolutionary trajectory of regional territorial patterns. The natural development scenario experienced the most intensive expansion of built-up land, with a newly increased area of 181.11 km². The ecological protection scenario can effectively curb the loss of ecological land and minimize the shrinkage of grassland resources. The cropland protection scenario is conducive to stabilizing cropland scale to the greatest extent and restraining the disorderly sprawl of urban land. The sustainable development scenario realizes coordinated and balanced changes in all land use types and delivers mutually beneficial progress between regional ecological conservation and socioeconomic development. Full article

This study investigates the geochemical distribution, integrated contamination status, and human health risks of potentially toxic elements (PTEs) in 31 agricultural topsoil samples collected from Najran, southwestern Saudi Arabia. As, Co, Cr, Cu, Ni, Pb, and Zn were measured and interpreted using spatial distribution maps, the pollution load index (PLI), Nemerow integrated pollution index (PN), chronic daily intake (CDI), hazard quotient (HQ), hazard index (HI), cancer risk (CR), and lifetime cancer risk (LCR) for both children and adults. The measured concentrations (mg/kg) varied from 2–8 for As, 2–14 for Co, 11–50 for Cr, 5–50 for Cu, 9–50 for Ni, 2–28 for Pb, and 10–249 for Zn. Based on mean values (mg/kg), the PTEs followed the descending sequence Zn (52.94) > Cr (26.68) > Ni (24.55) > Cu (16.68) > Co (6.81) > Pb (6.65) > As (4.45). PLI values ranged between 0.117 and 0.642, with an average of 0.355, suggesting generally low combined pollution by multiple elements across all sampling locations. However, PN values extended from 0.137 to 1.930, classifying 27 locations as safe, 2 as warning-level sites, and 2 as slightly polluted, mainly due to elevated Zn and Pb levels. The assessment of non-carcinogenic risk indicated no exceedance of the level of concern, as total HI values ranged from 0.156 to 0.678 for children and from 0.017 to 0.075 for adults. On average, children had HI values about 9.1 times higher than adults, with soil ingestion representing the principal exposure route. The element-specific mean HI results indicated that As and Cr were the dominant contributors to non-carcinogenic risk. Carcinogenic risk was assessed for As, Cr, and Pb. Total LCR values ranged from 1.005 × 10⁻⁵ to 4.387 × 10⁻⁵ for children and from 4.460 × 10⁻⁶ to 1.950 × 10⁻⁵ for adults, remaining within the widely accepted or tolerable risk range. Among the carcinogenic elements, Cr accounted for the highest proportion of total LCR, contributing 68.67%–69.66%, followed by As with 30.09%–31.07%, while Pb made a very small contribution of only 0.25%–0.26%. In spatial terms, the greatest HI and LCR values were concentrated mainly in the western to central-western agricultural areas, where several elements relevant to health risk were present together. Full article