Soil Particles Research Articles

Use of Wheat Fiber and Nanobentonite to Stabilize Clay Subgrades

Since clayey soils naturally present low mechanical strength, they pose direct challenges for engineering applications. Finding appropriate soil stabilizers to address the challenges posed by clayey soils is crucial for ensuring that the soil meets the necessary geotechnical requirements and fulfills economic and environmental issues. To this end, this research uses several stabilizers and techniques in clayey soils to improve their suitability for construction. The main objective of this study is to assess the use of wheat fiber and nanobentonite (NB) in soil stabilization, estimate their behavior in practices, outline their obstacles and potential for soil improvement, and consider their ecological and financial effects. This research also evaluates the behavior of the soil by incorporating NB (0.4, 0.8, and 1.2%) as a stabilizing agent. For this purpose, the randomly dispersed wheat fibers as a reinforcing agent at different dosages and lengths (0.3, 0.6, 0.9%, and 5, 10, and 15 mm) were combined to the soil matrix. The soil was characterized by conducting compaction, unconfined compressive strength (UCS), direct shear (DS), California bearing ratio (CBR), indirect tensile strength (ITS), freezing-thawing (F-T) tests, and microstructural analysis. The data were used to assess the effect of wheat fiber and NB on the soil’s geotechnical properties. The results revealed that incorporating 0.8% NB into the soil led to the best enhancement in compressive strength. This improvement is attributed to the dehydration and formation of a viscous-like film between the soil particles. In addition, 0.6% fibers with a length of 15mm increased the interaction and bonding forces between the particles of soil, resulting in a maximum increase in compressive strength. Combining fibers and NB improved the shear strength, tensile strength, and bearing capacity. Besides, the stabilized soil exhibited superior resistance to freezing-thawing cycles compared to the unreinforced clay. Overall, the results indicate that using wheat fibers and NB is a cost-effective and eco-friendly solution for stabilizing clay subgrades.

Relationship between soil structure and hydrological properties of the active layer in the permafrost region of the Qinghai–Tibet Plateau based on fractal theory

Soil structure and hydrological properties influence ecosystem stability and hydrological cycles. Fractal theory has been widely used in the quantitative analysis of soil particle-size distribution (PSD), aggregate and pore distribution, and evaluation of soil degradation, desertification, and wind erosion. However, the complex relationships between soil physiochemical properties and soil hydrological processes based on fractal theory have not been thoroughly investigated. This study focused on the correlation among soil structure, physicochemical properties, and hydrological properties in the active layers of various soil types and vegetation coverages in the permafrost region of the Qinghai–Tibet Plateau (QTP) using the principles of fractal theory. The results showed that the fractal dimension of soil PSD (DPSD) in the active layer of the QTP was predominantly within the range of 2.13–2.70, which is notably smaller than the fractal dimension of the soil water retention curve (DWRC: 2.72–2.93). With decreased vegetation coverage, the alpine soil particles exhibit gradual fineness, increasing the DPSD. Soil physicochemical properties were affected by the interactions among internal factors and the external environment, such as geographical locations, slope orientations, vegetation coverages, and soil freeze–thaw cycles. The results of correlation analysis indicated that the fractal dimension of PSD and the soil water retention curve (WRC) were significantly correlated with soil textural, physicochemical, and hydraulic properties, particularly in clay, silt, and very fine sand content. Finally, a fractal model of WRC in the permafrost region was established based on DPSD and WRC parameters of the Gardner and van Genuchten models. The study provides an improved perspective for revealing the transport process and influencing mechanism of soil water and salt in the active layer of the QTP and a more accurate prediction of soil physiochemical and hydrological properties for climate warming and wetting.

The synchronized dynamic release behavior of microplastics during farmland soil erosion process

Microplastics (MPs) are widespread in farmland soil. However, the risks associated with their loss through soil erosion remain unknown. This study investigates the occurrence and behavior of MPs in farmland soil in a southeastern coastal area of China, focusing on their synchronized dynamic release during soil erosion scenarios. The results showed that the abundance of MPs in the tested farmland soil ranged from 2.40×104 to 1.04×105 items·kg-1. MPs predominantly appear as fragments and particles, with sizes concentrated between 30-100 μm. During the process of soil erosion, characterized by rapid soil subsidence, the amount of MPs released into water bodies initially decreases, averaging a reduction of 1.08×104 items·kg-1. This is followed by an average increase of 1.89×104 items·kg-1. The competition between the adsorption, collision, and sedimentation of soil particles and the desorption and release of settled particles, determines this behavior. This pattern is strongly related to the physicochemical properties and mechanical composition of the soil. Deep learning predictions revealed that, without external influences, 49.42% of MPs in farmland soil could be synchronously released into water bodies during erosion. The analysis shows that MPs exhibit dynamic behavior in time and space, posing serious threats to aquatic ecosystems. Controlling soil erosion in farmland is crucial for the source management of MP migration.

Mechanical Characteristics and Microstructural Changes in Phosphogypsum-Cement-Lime Composite Modified Loess

Loess is widely distributed in China but suffers from inherent deficiencies limiting its direct use as a subbase material in road construction without modifications. This study investigated the utilization of Phosphogypsum (PG), an industrial waste, in a composite stabilizer containing cement, lime and slag powder for modifying loess in the subbase application. An orthogonal test design was employed to optimize the composite proportions. Laboratory tests evaluated the mechanical properties including unconfined compressive strength (UCS), splitting tensile strength, resilient modulus and water stability of modified loess over curing periods up to 90 days. Microstructural evolution was analyzed using X-ray diffraction (XRD) and scanning electron microscopy (SEM). Results showed the composite containing 25% PG, a cement-slag ratio of 4:6 and 5% lime imparted the highest strengths. Mechanical performances increased with curing time and stabilizer content. Water stability and heavy metal immobilization were satisfactory. Microstructural results revealed microstructural densification occurred through hydration product development binding soil particles. This work demonstrated the technical and environmental viability of recycling PG through loess improvement, offering a sustainable solution for problematic soil stabilization and industrial waste utilization.

A machine learning framework to measure Water Drop Penetration Time (WDPT) for soil water repellency analysis

The heat from wildfires volatilizes soil’s organic compounds which form a waxy layer when condensed on cooler soil particles causing soil to repel water. Timely assessment of soil water repellency (SWR) is critical for prediction and prevention of detrimental impacts of hydrophobic soils such as soil erosion, reduced availability of water to plants, and water runoff after rainfalls leading to floods. The Water Drop Penetration Time (WDPT), i.e., the time elapsed from a drop landing on the soil surface to its complete absorption is commonly used to assess the SWR level. Its manual measurements have variability based on the used instruments and subjective observations. The goal of this work is to design an automated system to perform standardized WDPT tests and assess the SWR levels. It consists of an electronically controlled mechanism to release a water drop, and a video camera to record the water penetration process. The latter is modeled as an “action” in video and Temporal Action Localization (TAL) analytics is used for predicting the WDPT and assessing the SWR level.

Modeling and Parameter Selection of the Corn Straw–Soil Composite Model Based on the DEM

During corn harvesting operations, machine–straw–soil contact often occurs, but there is a lack of research related to the role of straw–soil contact. Therefore, in this study, a composite contact model of corn straw‒soil particles was established based on the discrete element method (DEM). First, the discrete element Hertz‒Mindlin method with bonding particle contact was used to establish a numerical model of the double-bonded bimodal distribution of corn straw, and bonding particle models of the outer skin‒outer skin, inner pulp‒inner pulp, and outer skin‒inner pulp were developed. The nonhomogeneous and deformable material properties were accurately expressed. The straw compression test combined with simulation calibration was used to determine some of the bonding contact parameters by means of the PB (Plackett–Burman) test, the steepest ascent test, and the BB (Box–Behnken) test. Additionally, Additionally, the Hertz-Mindlin with JKR (Johnson-Kendall-Roberts) + bonding key model was used to establish the numerical model of the soil particles, which was used to describe the irregularity and adhesion properties of the soil particles. The geometric model of the soil particles was established using the multisphere filling method. Finally, a composite contact model of corn straw‒soil particles was established, the contact parameters between straw and soil were calibrated via collision tests, inclined tests and inclined rolling tests, and the established composite contact model was further verified through direct shear tests between straw and soil. A theoretical foundation for the optimal design of equipment linked to maize harvesting is provided by this work.

Impact of Agricultural Activities on Soil Particle Size, pH, and Organic Matter in the Dimonika Biosphere Reserve, Mayombe (Republic of Congo)

Land-use change disrupts several soil physico-chemical parameters. This study aimed to analyze the influence of agricultural activities, topography, and localities on soil texture, pH, and organic matter in the Dimonika Biosphere Reserve. To achieve this, 90 soil samples were collected using an auger based on land use types, topography, and localities. Analyses of soil texture, pH, total organic carbon (TOC), and total nitrogen (TN) were conducted at the IRSEN laboratory in Pointe-Noire. The results showed that clay texture predominates in the studied area, which is related to the nature of the soils. The Kruskal-Wallis ANOVA test highlighted a significant effect of agricultural activities on soil acidity, with an acidic pH ranging from 4.2 to 5 in cultivated areas, compared to a very acidic pH (3.5 to 4.2) in mature forests. However, neither topography nor localities affected pH. Total organic carbon significantly decreased in old plantations (1.3±0.3%) and fallows (1.5±0.5%) compared to mature forests (1.9±0.5%) and savannahs (2.3±0.6%), while total nitrogen showed no notable variations. Topography also had no influence on organic status (TOC, TN). However, at the local level, the Makaba area stood out with significantly higher TOC (2±0.5%) and TN (0.2±0.03%) compared to Les Saras (0.14±0.03%) and Kayes (0.16±0.2%). The C/N ratio, influenced only by agricultural activities, was below 15, indicating rapid organic matter mineralization and a low TOC content. Several potential solutions were proposed for sustainable soil management.

Insights into pupal development of Bactrocera dorsalis: factors influencing eclosion.

In the life cycle of the oriental fruit fly where larvae reside within fruits and adults exhibit high activity, the pupal stage occurs in the soil, closely tied to agricultural soil management. This study investigates the impact of four variables (body orientation, burial depth, soil particle size, and pH) on Bactrocera dorsalis' physiological preferences, eclosion rates, and pupal stage duration. Notably, body orientation, burial depth, soil texture (particle size), and pH affect eclosion rates. The fruit fly demonstrates a preference for a supine position during eclosion, with average eclosion rates of 97.33%, contrasting with decreases to 78.00% in a head-down position. Soil with mixed particle sizes is detrimental to pupal eclosion, reducing the eclosion rate to 56.67%. And at a pH of 9.98, eclosion rates decrease to 16.67%. These factors significantly influence eclosion rates However, these factors do not significantly alter the duration of the pupal stage, with mean changes not exceeding one day when experimental conditions are modified. These findings suggests that soil manipulations affecting these variables could reduce eclosion rates without compromising the uniformity of adult emergence. This study provides a foundation for environmentally friendly pest control practices and addresses gaps in the pupal stage research of the oriental fruit fly.

Relationship Between Salt Accumulation and Soil Structure Fractals in Cotton Fields in an Arid Inland Basin

The relationship between soil structure and salt accumulation is unclear; thus, experiments on salt accumulation under different soil structures were conducted in cotton fields in arid areas of northwest China. Thirty-nine sets of soil samples were collected from the 0 to 180 cm profile of three experimental areas. The total salt content of the soil extracts and the particle size distribution of the soil samples were determined using a JENCO TDS and a laser particle size analyzer, respectively, and the fractal dimension of the soil structure was obtained using fractal theory. Pearson’s correlation analysis and Tukey’s test (p < 0.01) were used to analyze the correlation between soil salinity, soil particle size distribution, and fractal dimensions in the three profiles. The results showed soil salinity accumulation was affected mutually by soil texture and soil structure, and soil salinity tended to accumulate in fine-grained soil. The soil fractal dimension (D) could indicate soil texture and quantify soil salinity content. When the sand content was more than 50%, there was a significant positive correlation between the soil fractal dimension and soil salinity (correlation coefficient R = 0.943). The results provide valuable insights into cotton production in arid areas.

CO₂ sequestration and soil improvement in enhanced rock weathering: A review from an experimental perspective

AbstractEnhanced rock weathering (ERW) is an emerging negative emission technology (NET) with significant potential for mitigating climate change and improving soil health through the accelerated chemical weathering of silicate minerals. This study adopts a critical research approach to review existing ERW experiments, focusing on the mechanisms of soil improvement and CO₂ sequestration, as well as the economic costs and environmental risks associated with its large‐scale implementation. The results demonstrate that while ERW effectively enhances soil pH and provides essential nutrients for crops, its CO₂ sequestration capacity is highly dependent on variables such as soil type, rock type, application rate, and particle size. Furthermore, the economic feasibility of ERW is challenged by high costs related to mining, grinding, and transportation, and environmental risks posed by the release of heavy metals like Ni and Cr during the weathering process. Notably, significant discrepancies exist between laboratory experiments and field applications, highlighting the need for extensive in‐situ monitoring and adjustment of ERW practices. This study underscores the importance of optimizing ERW strategies to maximize CO₂ sequestration while minimizing environmental impacts. Future research should focus on long‐term field experiments, understanding secondary mineral formation, and refining the application techniques to enhance the overall efficiency and sustainability of ERW. © 2024 Society of Chemical Industry and John Wiley & Sons, Ltd.

Acidified biochar one-off application for saline-alkali soil improvement: A three-year field trial evaluating the persistence of effects

Salinization is a global soil degradation issue threatening agricultural productivity and environmental sustainability. Native biochar is a promising soil amendment, but its high alkalinity limits its use in saline-alkali lands. Acidified biochar, with a lower pH, is theoretically more suitable. This study aims to evaluate the persistence of effects of acidified biochar one-off application on soil particle size distribution, physicochemical properties, water retention, temperature regulation, and evaporation conditions of saline-alkali soil, thereby verifying its feasibility and exploring the optimal application range. We conducted a three-year cotton field experiment using palm fruit branch biochar as the raw material, acidified with ferrous sulfate, which involved four biochar applications (0, 10, 20, and 30 t ha−1) and four irrigation quotas (60 %, 80 %, 100 % and 120 % ETc). The results indicated that the initial acidified biochar application slightly increased surface soil (0–20 cm) pH by 0.1 %–3.9 %, this negative effect was nearly eliminated by the third year. Biochar application significantly altered surface soil particle size distribution, increasing sand content by 1.6 %–8.4 %, and persistently improved soil hydraulic properties, with water holding capacity still showing a 6.5 %–16.7 % increase in the third year. Biochar enhanced soil thermal insulation and suppressed soil evaporation, but these benefits gradually diminished with increasing cultivation years. Acidified biochar effectiveness was closely linked to irrigation quota. Significant differences in soil water and heat indicators were observed between the 20 and 30 t ha⁻¹ biochar treatments only under low irrigation quotas. Under sufficient irrigation (100 % and 120 % ETc), the optimal biochar application range was 15–20 t ha⁻¹, while under low irrigation (60 % and 80 % ETc), the optimal range was 20–25 t ha⁻¹. This study demonstrated that acidified biochar one-off application has significant multi-year benefits in improving soil structure and hydrothermal properties, providing a scientific basis for the improvement and sustainable utilization of saline-alkali soil.

Viscosity Reduction and Drag Reduction Performance Analysis of Bionic Excavator Buckets Based on Discrete Element Method

With the aiming of solving problems with the existing ordinary excavator buckets used in the process of operations (such as heavy digging resistance, ease of adhesion, and others), seven types of bionic buckets and a prototype bucket were designed, based on the contractile-state curve of the earthworm head and the contour curve of the pangolin claw toe. The digging processes of the buckets were simulated using the discrete element method. The results show that, compared with the prototype buckets, all seven types of bionic buckets have significant drag reduction effects at the same digging depth, and the drag reduction effects increase with the decrease of digging speed. Among them, the composite bionic bucket-3 has the highest drag reduction rate, of 14.469% when the digging speed is 2 rad/s. At the same digging speed, different buckets disturb the soil particles to different degrees, and the bionic buckets disturb the soil more significantly compared with the prototype buckets. By conducting contact force field analysis for the buckets, it was shown that the bionic corrugated structure brings the bucket surface into incomplete contact with the soil particles, where the contact is on small areas or even on points, so that the relative velocity between the soil and the shovel body increases under the same driving force, which reduces the excavation resistance. This study provides a theoretical and design basis.

Simulation of landslide dam failure due to overtopping considering wide-graded soil erosion

Landslide dams, as a particular type of secondary geological disaster, can cause serious flood disasters. Therefore, accurately predicting potential dam failure processes is crucial for developing reasonable emergency response plans. Currently, several landslide dam failure models have been proposed, but most of these models do not appropriately consider the wide gradation of landslide dam materials, which is essential for accurate erosion calculations. Therefore, this research proposes a relative exposure formula under three-dimensional conditions to account for the concealment and exposure effects between large and small particles in wide-graded soil. Based on this, the incipient velocity of wide-graded soil is derived, and a mathematical model of overtopping failure of landslide dams is established. As part of the model, a numerical solution process is also developed to ensure convergence. To evaluate the performance of this new mathematical model, the discharge process of Tangjiashan landslide dam was used as a real-world case for dam failure calculation. The calculated results of key dam failure outcomes were compared with actual measurements, showing that the results of this model are largely consistent with actual measurements, with the error controlled within 10%. Additionally, the mathematical model proposed in this article was compared with two other existing dam failure models, revealing that the model proposed here has advantages in controlling the error of key dam failure outcomes, mainly due to the comprehensive consideration of erosion calculation in wide-graded soil. To further evaluate the stability of the model, the breach processes of the “11.3” Baige landslide dam and the Yigong landslide dam were also calculated, and the results showed reasonable consistency. Based on the model presented in this article, the influence of the grading width of landslide dam materials on key dam failure outcomes was discussed. It was found that grading width significantly affects the development process of breach flow. Specifically, wider grading width leads to smaller peak values of breach flow and later peak times. Additionally, the final size of the breach is affected by grading width, as it has a significant impact on erosion strength, although the sensitivity of this parameter is relatively weak. Given the significant impact of grading width on the dam failure process, especially for landslide dams containing wide-graded soil, it is essential to fully consider the wide grading of materials for accurate dam failure calculations.

Wear and Damage Study of Straw Chopper Knives in Combine Harvesters

Most of the biomass of cereal straw is chopped and left on the field as organic fertilizer, but its conversion into fertilizer depends on the quality of chopping, which is influenced by the wear of the chopping blades. The aim of the study was to determine the influence of the contamination of the cereal straw on the wear of the combine chopper blades. The study was conducted during the harvest in 2022, when 30 ± 1% of the grain was lodged and contaminated with abrasive soil particles (poor conditions), and in 2023, when the straw was unlodged and clean (excellent conditions). Six sets of blades with different mechanical and geometric properties were selected. The results showed that the wear ranges were very different: 1.47–2.99 g/100 ha in 2022 and 0.72–2.14 g/100 ha in 2023. For micro-abrasive wear, the hardness of the blades (349–568 HV) and the cutting edge angle (20°–29°) were important factors of their wear resistance. When the clean straw was chopped, the influence of the blade hardness and cutting edge angle on wear was not significant, and the wear was less. The wear of the blades had a sinusoidal character, which was related to the position of the blades on the chopping drum. This character depends on the design of the chopper and not on the straw quality.

TXNIP regulates pulmonary inflammation induced by Asian sand dust

Asian sand dust (ASD), a seasonal dust storm originating from the deserts of China and Mongolia, affects Korea and Japan during the spring, carrying soil particles and a variety of biochemical components. Exposure to ASD has been associated with the onset and exacerbation of respiratory disorders, although the underlying mechanisms remain unclear. This study investigates ASD-induced pulmonary toxicity and its mechanistic pathways, focusing on the role of thioredoxin-interacting protein (TXNIP). Using TXNIP knock-out (KO) mice and adeno-associated virus (AAV)-mediated TXNIP overexpression transgenic mice, we explored how TXNIP modulates ASD-induced pulmonary inflammation. Mice were exposed to ASD via intranasal administration on days 1, 3, and 5 to induce inflammation. ASD exposure led to significant pulmonary inflammation, evidenced by increased inflammatory cell counts and elevated cytokine levels in bronchoalveolar lavage fluid, as well as heightened protein expression of the TXNIP/NOD-like receptor pyrin domain-containing 3 (NLRP3) inflammasome. TXNIP KO mice exhibited attenuated airway inflammation and downregulation of the NLRP3 inflammasome compared to wild-type controls, while AAV-mediated TXNIP overexpression mice showed exacerbated inflammatory responses, including elevated NLRP3 inflammasome expression, compared to AAV-GFP controls. These findings suggest that TXNIP is a key regulator of ASD-induced pulmonary inflammation.

Variability of Soil Aggregate Disintegration During Splash Erosion Under Different Circumstances

ABSTRACTThe duration of rainfall is a significant factor in the process of splash erosion. Nevertheless, there is a lack of comprehensive documentation regarding the extent and characteristic of soil aggregate disintegration resulting from raindrop impact during splash erosion. To examine the properties of the aggregate disintegration mechanism during various of splash erosion, three soil samples (S‐1, S‐2, and S‐3 labeled as the organic matter was 19.77, 31.70, and 26.83 g kg−1) were employed to simulated splash erosion under six durations of rainfall (5, 10, 15, 20, 30, and 40 min). Aggregates ranging in size from 1 to 5 mm were utilized in the preparation of test soils for different antecedent moisture contents (3%, 5%, 10%, and 15%). The result demonstrated that the slaking effect, as observed in the fast wetting of the Le Bissonnais method, is attributed to the sudden release of air entering the water, irrespective of the water immersion duration. Upon increasing moisture content, under fast wetting conditions, the mean weight diameter (MWD) values for S‐2 and S‐3 samples increased from 1.25 and 1.31 to 1.85 and 1.61, respectively. Subsequently, at a moisture content of 10%, the MWD decreased to 1.84 and 1.49 for S‐2 and S‐3 samples, respectively. In contrast, S‐1 sample exhibited an increasing trend from 0.34 to 0.93. The sensitivity of aggregates to disintegration from slaking (RSI) decreased by 0.58, 0.43, and 0.29, while mechanical impact (RMI) decreased by 0.23, 0.11, and 0.08 with increasing moisture content, respectively. The rate of splash erosion for the S‐1 sample exhibited an initial increase followed by a subsequent decrease as the duration of rainfall increased. The S‐1 sample, with the lowest organic matter content, exhibited the highest content of microaggregate content (< 0.25 mm) of splashed particles (referring to soil particles transported out of the splash area by raindrops), ranging from 31.62% to 65.57%. The content of macroaggregate (> 0.25 mm) in the residual soil (indicating soil particles that were left in the area affected by splashing) exhibited a gradual reduction as the duration of rainfall increased. As the soil reached saturation, the influence of physicochemical dispersion became more pronounced with the prolonged duration of rainfall. The forces of slaking and physicochemical dispersion predominantly disrupted > 1 mm aggregates, while the destruction of aggregates within the 0.25–1 mm range was insufficient. This study is valuable for understanding the splash erosion process and provides a scientific foundation for the improvement of soil erosion prediction models.

Research on adhesion properties of tidal flat soil on metal surface and discrete element simulation

The adhesion property of soil on the metal surface was tested by the orthogonal experiment with 4 factors and 3 levels based on piston pull out method. A regression model of adhesion stress and the factors including moisture content(X1), pressing time(X2), settling time(X3) and separation velocity (X4) was established. The experiment results show that the influence of each factor on adhesion stress is ranked as X1≈X2≈X3>X4>X3X4, and the adhesion stress shows an ‘S’ curve with the increase of separation velocity. The DEM parameters of the soil were calibrated based on the test results, and the contact and disturbance state of soil particles during the test were studied by discrete element method (DEM) using JKR model. The simulation tests show that the maximum adhesion stress occurs when the particles are about to separate from the probe surface, and the soil disturbance state is hierarchical.

Source identification and human health risk to polychlorinated biphenyls in public parks and playground surface soils, southern zone of Ghana.

Polychlorinated biphenyls (PCBs) constitute a typical example of persistent organic pollutants (POPs) that have been detected globally in most environmental media. Soil serves as a critical reservoir for PCBs. This research is aimed at evaluating the potential exposure and associated health risks posed by soil-laden PCBs to humans during outdoor activities on public playgrounds and parks within the southern zone of Ghana where limited studies have been undertaken. Surface soils collected from 56 sites were processed and analyzed for seven indicator PCBs in soil particle sizes less than 63µm. A multi-residual analytical approach for the simultaneous analysis of PCBs and polycyclic aromatic hydrocarbons (PAHs) via gas chromatography tandem mass spectrometry was utilized. The results indicated that the concentration of PCBs ranged from 0.26 to 24.00µg/kg with an average total concentration of 1.86 ± 3.23µg/kg which is below the environment guideline threshold of 1.3mg/kg stipulated by the Canadian Council of Ministers for residential playgrounds/parkland soils. Multivariate analysis showed that the sources of the PCBs could be attributed predominantly to historical release, atmospheric transfer, and deposition. The excess lifetime cancer risks posed to children and adults are less than 10-6 thereby implying the existence of low carcinogenic health risk to the human populace within the southern zone of Ghana. Thus, the conduct of outdoor activities at the public playgrounds/parks within these highly populated areas poses no significant risk to human health.

Experimental investigation on treatment of high-water-content dredged slurry with vacuum preloading-airbag pressurization

This paper offers valuable insights for advancing the consolidation of dredged slurry, alleviating blockage, and the application of vacuum preloading-airbag pressurization (VP-AP) technology in engineering practice. This study conducted laboratory model tests on the consolidation of sludge using prefabricated vertical drains-vacuum preloading, prefabricated horizontal drains-vacuum preloading, and VP-AP methods to further investigate the effectiveness of the VP-AP technique in strengthening the consolidation of dredged slurry. Comparative analysis was conducted on the macroscopic and microscopic differences in soil drainage characteristics, settlement, water content, shear strength, and soil particle morphology under the three treatment methods. The results show that the VP-AP method surpasses traditional vacuum preloading techniques in soil consolidation, effectively guaranteeing the consolidation of deep soil layers and enhancing the uniformity and stability of foundation strength. In addition, the microstructural analysis reveals that the VP-AP method can effectively mitigate the decrease in drainage efficiency caused by the clogging of the PVD and improve the structure of the soils, allowing a significant increase in the mechanical properties of the soils. In conclusion, the VP-AP technology demonstrates significant advantages in drainage efficiency, consolidation effectiveness, thus it has a widespread application potential in engineering practices for treating soft ground and deserves further in-depth study.

Strength and dilatancy of an unsaturated expansive soil at high suction levels

A series of suction-controlled triaxial tests was conducted on Nanyang expansive clay to investigate the effects of dry density and suction on dilatancy and strength. The suction of the soil samples was controlled using a vapour equilibrium technique, with four suction levels ranging from 3.29 MPa to 198.14 MPa, where water retention is dominated by adsorption. The experimental results show that the tested soil exhibits a brittle failure mode under high suction, significantly distinguishing the hydro-mechanical behaviour of the soil at high suction from that observed at low suction. This brittle failure mode significantly increases the contribution of suction to peak strength compared to residual strength, causes the soil to fail before reaching the critical state, a phenomenon not observed in soils under high suction, and results in dilatancy caused by damage to the soil particle aggregates rather than particle rearrangement. The dilatancy data obtained from the triaxial tests reveal that significant soil dilatancy occurs during shear after reaching peak strength, with the maximum dilatancy angle increasing with suction and decreasing with confining pressure. However, the initial dry density has a negligible impact on the soil's dilatancy under high suction levels. This observation further supports that, for unsaturated soils under high suction levels, dilatancy is attributed to damage to soil particle aggregates rather than the rearrangement of soil particles.