Soil Stabilization Research Articles

Three-Dimensional Spectral Element Method Implementation for Evaluating Rooted Soil Behavior in Slope Stability Analysis

Bioengineering techniques are being increasingly adopted as a sustainable solution to soil slope instability. Despite their recognized benefits, however, the mechanistic contribution of vegetation to slope stability remains inadequately understood due to the intricate nature of soil–root interactions and the complexity of root architectures. Most existing research predominantly offers qualitative assessments of vegetation effectiveness. This study aims to numerically substantiate the role of vegetation as a bioengineering technique for soil slope stabilization. Various plant species used commonly for soil stabilization were identified, and undisturbed soil samples were collected to quantify the shear strength parameters of the soils from both barren and vegetated slopes, along with root tensile strengths. A comprehensive topographic survey was conducted to capture the precise topography of the study area. Utilizing these primary data, in this work we develop 3D models for five representative plants within each species category and employ the Spectral Element Method (SEM), an advanced higher-order formulation of the finite element method (FEM), within the 3D domain to evaluate the factor of safety for the soil slopes. The SEM offers superior accuracy and stability in numerical computations. The results obtained through the SEM were corroborated through the FEM modeling and were found to be consistent with other established methodologies. This innovative approach of 3D SEM aims to quantitatively assess the impact of vegetation on soil slope stability and provide a more rigorous understanding of bioengineering applications in geotechnical engineering.

Effects of electrokinetic stabilization combined with addition of calcium ions on soil shear strength characteristics in the hilly granitic region of southern China

Enhancing soil shear strength is of great importance in preventing soil collapse and erosion in the hilly granitic region of southern China. However, limited studies have been conducted on improving soil shear strength in collapsing gullies. Electrokinetic stabilization (EKS) involves applying an electrical current through a soil mass to promote the migration of chemicals from injection points, thereby altering the chemical composition of the treated soil to improve its physical properties. In this study, the effects of calcium chloride (CaCl 2 ) addition and EKS techniques on the soil shear characteristics (shear strength, and its two components: cohesion and internal friction angle) of three different soil layers in collapsing gullies were investigated. The results showed that the EKS techniques significantly increased the migration of calcium ions from the anode to the cathode region of the power supply device used in the soils. Using EKS process alone did not increase or even decrease the soil shear strength, but combining EKS with CaCl 2 injection (Ca-EKS) increased the soil shear strength, and this increase was mainly due to the increasing the soil cohesion. The soil cohesion after Ca-EKS treatment increased on average by 49.84%, 83.11%, and 100.36% compared with the soil without treatments (CK) for the red soil, sandy soil, and detritus, respectively. However, soil amended by sole CaCl 2 addition, Water-EKS or Ca-EKS all can not increase soil internal friction angles compared with the CK. These results demonstrated that the application of Ca-EKS can be applied to improve the soil shear strength and stability of gully walls in hilly granitic regions.

Effects of Terracing on Soil Aggregate Stability and Erodibility in Sloped Farmland in Black Soil (Mollisols) Region of China

Soil aggregates are important indicators of soil structure stability and quality. The black soil region of northeast China, known for its high agricultural productivity, faces significant challenges due to soil erosion. This study investigates the impact of terracing on the stability and erodibility characteristics of soil aggregates in sloped farmlands, which is crucial for this important agricultural area. Three research sites with the same basic management modes were selected along a latitudinal gradient, from the mid-temperate zone to the cold temperate zone, in the black soil region of northeast China. The Savinov method was used to analyze the differences in soil aggregate size distribution, stability characteristics, and soil erodibility between terraced and non-terraced slopes at each research site. The results showed that terracing increased the content of large soil aggregates (>0.25 mm) by 5.38–6.35%, with the increase becoming more pronounced from north to south. The improvement in soil structure varied by location and slope position, with the most significant improvement at the middle slope position. Terracing enhanced soil aggregate stability, reduced soil erodibility, and improved soil structure by increasing clay and soil organic matter (SOM) content and reducing soil bulk density (BD), promoting the conversion of small aggregates to large aggregates. Soil stability indicators such as water-stable aggregates (WSAs), mean weight diameter (MWD), and geometric mean diameter (GMD) were dominated by aggregates > 5 mm, while erodibility indicators such as fractal dimensions (Ds) and the soil erodibility factor (K values) were mainly influenced by aggregates < 0.25 mm. Terraces can improve the soil structure and stability of sloping farmland by increasing the content of large soil aggregates and enhancing overall soil quality. The benefits of these improvements increase with latitude. These findings provide critical insights for determining effective management practices for sloped farmlands in the black soil region under various site conditions. They offer scientific evidence for preventing soil erosion and improving soil quality, thus supporting the sustainable development strategy for protecting black soil and ensuring long-term agricultural productivity.

Environmental Sustainability of Pile Construction Activities in Nigeria; Strategies and Best Practices

: Pile construction activities is a multifaceted activity among the construction activities that are performed by heavy machines, materials and energy sources generating environmental impacts associated with pilling activities such as carbon emissions, noise, heavy vibration, soil instability and groundwater pollution. Sustainable piling construction guarantees that the whole piling process meets environmental sustainability and ultimately human health and wellbeing. Data were gathered through a questionnaire survey administered to construction professionals including engineers, project managers, surveyors, and builders. Out of the 50 questionnaires distributed, 41 responses were analyzed. The study employed the Relative Importance Index (RII) to rank the effectiveness of various strategies in mitigating environmental impacts. The findings underscore the critical role of introducing low-emission machinery and optimizing operational hours in reducing carbon emissions. Noise management was most effectively achieved through alternative pile installation methods combined with regular equipment maintenance. Maintaining adequate setbacks from structures and employing controlled installation techniques were identified as essential strategies to mitigate vibration. Addressing soil instability was found to rely heavily on thorough site investigations and the implementation of effective ground stabilization techniques and preventing groundwater pollution requires the proper use of drilling fluids and diligent site management. These findings contributed to the development of environmentally sustainable practices in pile construction, emphasizing the importance of comprehensive strategies to mitigate the adverse environmental impacts of such activities in Nigeria.

GENETIC DIVERSITY AND POPULATION STRUCTURE OF JUNIPERUS SERAVSCHANICA KOM. IN CENTRAL ASIA REVEALED BY MICROSATELLITE MARKERS

Juniperus seravschanica Kom. is a widely distributed and significant tree species in Central Asia, thriving in the mountain ranges from Oman to Uzbekistan, Kyrgyzstan, and Kazakhstan. It plays a vital role in forming shrub-forest massifs in mountainous regions, contributing to soil drainage and stabilization at medium to high altitudes. To gain a detailed understanding of the current status of J. seravschanica and to develop effective conservation strategies, a comprehensive study of the species' genetic diversity and population structure was conducted. Leaf samples were collected from 15 J. seravschanica populations across Uzbekistan, Kyrgyzstan, and Kazakhstan to assess genetic diversity and population structure. Using 11 polymorphic simple sequence repeat (SSR) markers, genetic diversity parameters such as the number of alleles, the number of effective alleles, the percentage of polymorphic loci, and Nei's genetic diversity index were evaluated. Nei's genetic diversity index for J. seravschanica populations averaged 0.450, ranging from 0.407 to 0.566. The AMOVA revealed that 90.3% of the total genetic variation was within populations, indicating a high level of genetic diversity within each population. Gene flow, calculated using alleles from all populations, was estimated at 4.654. Population structure analysis showed weak clustering among the studied populations, supporting the AMOVA findings. This study provides valuable insights into the genetic diversity and population structure of J. seravschanica in Central Asia. The high genetic diversity within populations suggests a strong adaptive capacity to environmental changes. These findings can be effectively utilized to develop conservation strategies for J. seravschanica, ensuring the long-term sustainability of this important tree species in Central Asia. This work was supported by Grant No.AP09259027 of the Science Committee of the Ministry of Science and Higher Education of the Republic of Kazakhstan.

Tiny Architects of Fertile Soils: Understanding the Role of Soil Arthropods

Soil Arthropods are a vitally important component of the ecosystem, as their diversity, abundance, and distribution pattern play a vital role in ecosystem sustainability. Soil arthropods are critical to maintaining soil fertility and ecosystem health by driving essential ecological processes such as nutrient cycling, decomposition, and soil structure formation. As decomposers, these organisms, including mites, springtails, isopods, termites, and others, break down organic matter, aiding in the recycling of key nutrients like nitrogen and phosphorus, vital for plant growth. By burrowing and tunnelling, arthropods improve soil aeration, water infiltration, and aggregation, contributing to soil stability and resistance to erosion. Despite their small size, soil arthropods are essential ecosystem engineers, influencing the dynamics of microbial communities and facilitating the conversion of organic material into accessible forms for other organisms. However, their populations face threats from land-use changes, unsustainable agricultural practices, and the introduction of invasive species, all of which degrade soil health. Conservation strategies focused on habitat restoration, sustainable farming, and public awareness are crucial to protecting these vital organisms and ensuring the long-term sustainability of soils. A greater understanding of the roles played by these often-overlooked organisms can enhance conservation efforts and foster more sustainable agricultural practices, thereby supporting global ecosystem health.

The effect of mosses on the relocation of SOC and total N due to soil erosion and percolation in a disturbed temperate forest

Forests cover one-third of the global land and are important components of carbon and nitrogen cycling. Anthropogenic disturbances, such as forest road systems or skid trails for timber harvesting, can dramatically change the nutrient cycling in these ecosystems. Skid trails increase soil erosion and thus the displacement of soil organic carbon (SOC) and total nitrogen (Nt). Additionally, runoff transports high amounts of dissolved organic carbon (DOC), which can have a negative impact on aquatic ecosystems. One of the most important countermeasures against soil erosion is the quick recolonization of vegetation. To date, the extent to which natural vegetation succession influences the relocation of SOC and Nt, and in particular the role of mosses in this context, has not been well investigated. This study investigates the influence of natural vegetation succession and in particular of mosses on the displacement process of SOC and Nt as well as DOC caused by soil erosion. To this end, we combine the results of a field study using in-situ rainfall simulations with small-scale runoff plots in skid trails of the Schönbuch Nature Park in southwestern Germany with the results of ex-situ rainfall simulation experiments with infiltration boxes containing the substrate from the respective skid trails. The eroded sediments of skid trails were on average enriched in SOC by 16% and in Nt by 35% compared to the original soil, which lead to a decrease of the C/N ratio in sediments. As vegetation succession progressed, the displacement of SOC and Nt was reduced, confirmed by a negative correlation between the enrichment ratios of SOC (ERSOC), Nt and total vegetation cover. However, mosses tended to reduce ERSOC more than vascular plants. Additionally, mosses significantly decreased DOC concentration in surface runoff compared to bare soils, while no difference in DOC concentration in percolated water could be observed. Future research should explore the role of mosses in the storage of SOC and Nt in the soil and their impact on soil stability. Thus, utilizing mosses could potentially minimize environmental impacts from soil disturbances in forests.

Effect of Calcium Carbide Residue on Shrinkage Mechanism of Clayey Subgrade Soil

ABSTRACT Calcium carbide residue (CCR) has been identified as an effective replacement for traditional lime for the stabilization of expansive soils. The shrinkage of expansive clay severely threatens the foundation layers’ long-term stability. The efficacy of CCR stabilization in reducing compressibility and enhancing the strength and stiffness of clay has been widely reported; however, the calcium-based additive stabilized soil tends to lose its engineered integrity under field-exposed seasonal moisture variation, specifically, shrinkage induced by prolonged drying. In this study, the shrinkage characteristic of CCR-treated clay (6%, 9%, and 12%) slurry was investigated by digital image analysis and mercury displacement method to quantify volumetric shrinkage strain. The results were compared with those of 4% and 6% lime-treated clay, which revealed the higher efficacy of CCR in reducing shrinkage strain by 47–57%. A characteristic shrinkage curve that depicted the significant variation of shrinkage phases in CCR-treated clay samples is developed. The dominance of the proportional shrinkage phase is observed in both untreated and treated clay samples. The shrinkage caused by evaporation, hydration, and decalcification is postulated in treated clays. This study is expected to contribute to the understanding of shrinkage mechanisms of CCR-treated clay and assist in the future design of stabilized embankment sections or subgrade for unpaved roads.

Evaluating the strength characteristics of mixtures of municipal solid waste incineration bottom ash and reddish laterite clay for sustainable construction

This study examines effects of mixing municipal solid waste incineration bottom ash (MSWI-BA) with reddish laterite clay (RLC), evaluating factors such as vertical stress, mixing ratio, curing period, and the addition of lime. A total of 153 direct shear tests were conducted to thoroughly assess the mixture's strength characteristics. Vertical stress levels of 85.5 kPa, 172.4 kPa, and 259.3 kPa were used to simulate varying stress conditions, while mixing ratios of 40 %, 80 %, 100 %, and 120 % were applied to explore potential applications of recycled MSWI-BA with clayey soils. A fast-curing approach was employed, with curing periods of 24, 48, and 72 h, to investigate the time-dependent strength development under controlled conditions. A three-way ANOVA analysis confirmed that mixing ratio, curing period, and vertical stress significantly impacted both peak and residual shear strength. The 100 % MSWI-BA mixture, with or without 1 % lime, exhibited optimal performance, providing the pronounced shear strengths and dilative behavior. The study found that MSWI-BA significantly improved shear strength ratios compared to the RLC, with improvement ratios ranging from 1.439 to 2.460 across stress levels. Additionally, upper and lower bound equations for peak and residual strength ratios were developed, providing predictive tools for mixture design. Cohesion values in the range of 8.3–128.9 kPa and friction angles from 40.6° to 44.1° were achieved, surpassing or matching those reported in similar research. The study employed Bolton's (1986) dilatancy model, finding α values between 0.61 and 0.71, comparable to those in studies of granular materials. These results highlight the effectiveness of adding MSWI-BA and lime in enhancing reddish laterite soil stabilization through both chemical and mechanical means, making it a sustainable and cost-effective approach for civil engineering projects by improving material strength, reusing local soils, recycling waste, and reducing carbon footprints.

Old-growth Ficus trees provide soil water and carbon storage to urban greenspaces in a Brazilian metropolis

Urban flooding has been considered one of the most severe natural disasters around the world, and urban greenspaces can provide important flood regulation ecosystem services. In Belo Horizonte (Brazil), the woody vegetation, especially the old-growth Ficus trees, appears to protect an urban park against the flooding of the Arrudas river. Thus, we compared the soil water content, soil water-holding capacity, soil aggregation and porosity among a highly permeable urban park planted with herbaceous and woody species, including Ficus, a semi-permeable parking lot with only Ficus and an impermeable site without trees (Disturbed Site-DS). The soil water content and water holding capacity of the urban park did not differ from that of the Ficus site, but it was lower than DS. These results were correlated with soil organic matter (SOM) content, soil aggregation and porosity, suggesting that Ficus trees play an important role in the hydrological cycle. To understand how the Fiscus species provide such soil permeability, we compared the aboveground plant biomass, soil fertility and soil carbon sequestration (total soil carbon, soil organic matter, humic and fulvic acids and soil isotopic δ13 C) in plots with Ficus and without this species within the park as well as in a preserved urban forest and a disturbed square. The outstanding plant biomass produced by Ficus species explained the high soil carbon sequestration, particularly in humic organic matter, favouring soil aggregation, porosity and water retention. Therefore, Ficus species may be considered an exceptional C-sequestering species, contributing for soil stabilization and the hydrological cycle in urban greenspaces.

Review of Quantifying Slope Stability and Assessing Landslide Susceptibility in Sabah, Malaysia

Landslides affect 3.7 million square kilometers of land and affect around 5% of the global population. In Malaysia, 21,000 locations are prone to landslides, with 16,000 in Peninsular Malaysia, 3,000 in Sabah, and 2,000 in Sarawak. Factors contributing to landslides include geological factors, weather conditions, slope steepness, vegetation, and human activities. Rainfall and geological conditions are significant external and internal causes. Landslides can be mitigated using various construction techniques, such as contagious bored pile, guniting, and rock anchoring. Rainfall and landslides are closely related, with rainfall affecting soil stability and causing slope failure. Prolonged rainfall can decrease slope stability due to increased water infiltration, leading to landslides. Analysis of slope stability is crucial in geotechnical engineering, assessing the stability of natural and man-made slopes. It involves assessing soil properties and identifying potential failure surfaces. Limit Equilibrium (LEM) and finite element (FE) methods are commonly used for slope stability assessments. LEM divides failure mass into slices, while FEM maintains global equilibrium until failure occurs. Both methods offer advantages, such as revealing working stress deformations with realistic soil compressibility data and tracking progressive failure to shear failure.

Remediation of Arsenic and Heavy Metals and Soil Stabilization by Waste Chitosan based Biochar

Objectives : This study aims to evaluate the feasibility of converting waste chitosan adsorbents, laden with microalgae, into biochar for application as a stabilizing agent to remediate heavy metal-contaminated soil and improve soil quality.Methods : Waste chitosan adsorbents were converted into biochar through two processes: dry thermal carbonization at 400°C to produce pyrochar and hydrothermal carbonization at 200°C to produce hydrochar. The elemental compositions, surface functional groups, morphologies of the biochars were evaluated by elemental analyzer, FT-IR spectrometer, and SEM analysis. The arsenic and heavy metal adsorption characteristics of the produced biochars were assessed. Additionally, the produced biochars were applied as stabilizing agents to arsenic and heavy metal-contaminated soil with varying mixing ratios of 2, 5 and 10 wt%. After a one-week soil stabilization experiment, soil properties and TCLP(Toxicity Characteristic Leaching Procedure) leaching tests were conducted.Results and Discussion : The pyrochar produced from waste chitosan exhibited a porous structure with high pH (pH 10) and minimal surface functional groups. The hydrochar consisted of spherical particles with functional groups such as hydroxyl and amine groups on the surface, exhibiting a slightly acidic pH of 5.8. Pyrochar has a higher adsorption capacity for cationic heavy metals compared to hydrochar due to its porous structure and high pH. On the other hand, when applied to soil, hydrochar demonstrated superior stabilization efficiency for arsenic and heavy metals. This is attributed to the diverse surface functional groups containing oxygen on the hydrochar. The stabilization efficiency was influenced by the biochar mixing ratio, with a 5% hydrochar application resulting in 10-64% stabilization efficiency for all elements.Conclusion : This study confirmed that biochar produced from waste chitosan effectively stabilizes arsenic and heavy metals in soils. Additionally, the quantity of biochar used can impact its effectiveness in stabilization.

Assessment of urbanization impacts on soil erosion and groundwater recharge in Enugu, Southeastern Nigeria

The study of Land Use and Land Cover (LULC) in Enugu, southeastern Nigeria, is crucial for understanding its effects on erosion and groundwater recharge. Different LULC types, coupled with varying slope gradients and soil types, create a complex interaction that influences soil stability and water infiltration in the region. This research aims to assess the distribution of LULC types, slope gradients, and soil types in Enugu, and to evaluate their impacts on erosion rates and groundwater recharge potential. Data for LULC, slope gradients, and soil types were collected and analyzed to determine their spatial distribution and characteristics. The study employed GIS techniques to map these variables and assess their interactions. Erosion potential and groundwater recharge capacity were evaluated based on the characteristics of the LULC types, slopes, and soils. The analysis revealed that trees cover the largest area (3709.74 km²), playing a significant role in stabilizing the soil and reducing erosion through their extensive root systems and canopy cover. Rangeland (2631.81 km²) also contributes to soil stability, although less effectively than forested areas. Crops (192.40 km²) have mixed impacts on erosion depending on agricultural practices. Built areas (1162.69 km²) present challenges due to impervious surfaces, which increase surface runoff and reduce groundwater recharge. Slope gradients were found to correlate with erosion processes and groundwater dynamics. Gentle slopes (0 - 1.81 degrees) cover 1870.15 km² and facilitate infiltration, enhancing groundwater recharge. Moderate slopes (1.81 - 4.06 degrees), covering 3275.46 km², are more prone to erosion, while steeper slopes (4.06 - 11.73 degrees) covering 2176.54 km² experience accelerated runoff and increased erosion rates. The steepest slopes (11.73 - 44.06 degrees) are the most erosion-prone areas, requiring significant intervention. The soil analysis showed that Dystric Nitosols (4052.80 km²) with the lowest K-factor (0.0178) are least prone to erosion and have high infiltration capacity, making them beneficial for groundwater recharge. Plinthic Acrisols (2732.53 km²) and Ferric Acrisols (102.36 km²) exhibit moderate erosion susceptibility. Dystric Fluvisols (793.92 km²) with the highest K-factor (0.0223) are highly erosion-prone. Gleysols (20.69 km²) have low to moderate erosion susceptibility. The interplay between LULC types, slope gradients, and soil types significantly influences erosion and groundwater recharge in Enugu. The study highlights the need for targeted land management practices, such as afforestation, contour farming, terracing, and the use of cover crops to mitigate erosion and enhance groundwater recharge. This research provides a comprehensive analysis of the relationships between LULC, slope gradients, and soil types in Enugu, offering valuable insights for developing effective land management strategies to address erosion and groundwater recharge challenges.

The Role of a New Stabilizer in Enhancing the Mechanical Performance of Construction Residue Soils.

Urban construction generates significant amounts of construction residue soil. This paper introduces a novel soil stabilizer based on industrial waste to improve its utilization. This stabilizer is primarily composed of blast furnace slag (BFS), steel slag (SS), phosphogypsum (PG), and other additives, which enhance soil strength through physical and chemical processes. This study investigated the mechanical properties of construction residue soil cured with this stabilizer, focusing on the effects of organic matter content (Oo), stabilizer dosage (Oc), and curing age (T) on unconfined compressive strength (UCS). Additionally, water stability and wet-dry cycle tests of the stabilized soil were conducted to assess long-term performance. According to the findings, the UCS increased with the higher stabilizer dosage and longer curing periods but reduced with the higher organic matter content. A stabilizer content of 15-20% is recommended for optimal stabilization efficacy and cost-efficiency in engineering applications. The samples lost their strength when immersed in water. However, adding more stabilizers to the soil can effectively enhance its water stability. Under wet-dry cycle conditions, the UCS initially increased and then decreased, remaining lower than that of samples cured under standard conditions. The findings can provide valuable data for the practical application in construction residual soil stabilization.

Sustainable soil stabilization of expansive soil subgrades through lime-fly ash admixture

Expansive soils, known for their significant volume changes with moisture variation, pose severe challenges for construction and pavement integrity. This study investigates the stabilization of expansive subgrade soils using a lime-fly ash mixture, aiming to enhance engineering properties and reduce associated risks. Soil samples from Nashik, Maharashtra, India, were analyzed for their geotechnical properties, revealing high plasticity and expansive nature. The study utilized different proportions of lime-fly ash mixtures to assess improvements in the stabilized soils' Unconfined Compressive Strength (UCS) and California Bearing Ratio (CBR). Laboratory tests, including granulometry, SEM, and XRF, indicated significant changes in the soil's physical and chemical composition. The stabilization process showed a marked reduction in the Free Swell Index (FSI) and swelling pressure attributed to flocculation. The optimum mix ratio of 1:4 (lime: fly ash) demonstrated the most substantial improvement, with UCS increasing to 224 kPa and CBR values reaching 8%. Additionally, the elastic modulus of the stabilized subgrade showed considerable enhancement, indicating better load-bearing capacity and durability. A flexible pavement design was implemented on both untreated and treated subgrades, demonstrating a 28% cost reduction for the stabilized section. This research underscores the effectiveness of using a sustainable lime-fly ash blend in mitigating the challenges posed by expansive soils, offering a cost-effective and environmentally friendly solution for road construction. The findings provide a robust framework for engineers to improve the stability and longevity of pavements on expansive soils.

Long-term vegetation succession enhances the network complexity and stability of soil protozoan communities

Long-term vegetation succession is critical for the improvement of environmental quality and the restoration of ecosystem functions. As key links in the micro-food web, protozoa are widespread in the soil and are important participants in nutrient cycling and energy transfer. However, the effects of vegetation succession on soil protozoan communities compared to those on other soil microbial communities, such as bacteria and fungi, remain largely unknown. Here, a long-term vegetation succession sequence of approximately 160 years was selected to investigate the evolutionary characteristics and drivers of soil protozoan diversity, network stability, and community assembly processes. Soil protozoan alpha diversity increased significantly with vegetation succession, and beta diversity differed significantly between early and late successional stages. Microbial biomass is a key driver of soil protozoan diversity. In addition, the network robustness and complexity of soil protozoa increased significantly and stabilized during late successional stages. Soil microbes played a direct role in protozoan network stability, whereas abiotic factors played an indirect role, reflecting the trophic cascade in soil micro-food webs. The relative contributions of deterministic processes to the community assembly of soil protozoa increased progressively with vegetation succession, owing to multiple eco-selective mechanisms arising from environmental changes. Our results highlight the bottom-up effects of soil microbes on secondary consumer communities during natural restoration, providing new insights into the mechanisms underlying the maintenance of soil micro-food web diversity and stability across environmental gradients.

Poly-γ-glutamic acid enhanced the yield and photosynthesis of soybeans by adjusting soil aggregates and water distribution.

Poly-γ-glutamic acid (γ-PGA) is employed extensively in agriculture to enhance soil water retention; however, the underlying mechanism by which γ-PGA improves soil structure and soybean productivity in arid regions remains poorly understood. A micro-scale field experiment was conducted in the arid region of northwest China, employing five concentrations of γ-PGA to investigate its impacts on soybean yield, photosynthesis, and water-use efficiency, as well as soil aggregates and water distribution. The five levels of γ-PGA were 0 (CK), 10 (P1), 20 (P2), 40 (P3), and 80 kg ha-1 (P4). The results demonstrated that the application of γ-PGA significantly improved soybean yield, photosynthesis, and chlorophyll content. It resulted in a decrease in soil aggregate content with a maximumdiameter of less than 0.053 mm and an increase in the stability of soil aggregates in the uppermost layer of the soil (0-30 cm). The application of γ-PGA significantly increased soil water content, particularly in the uppermost layer of the soil, and effectively reduced water consumption and improving water use efficiency in soybeans. Overall, the P3 treatment exhibited the most pronounced improvement of soybean yield, photosynthesis, water-use efficiency, as well as distribution of soil aggregates and water. The correlation matrix heatmap also revealed a strong correlation between improvement of soybean yield or photosynthesis at various γ-PGA application levels and the enhancement of soil stability or soil water content. The multivariate regression analysis revealed that an optimal application level of 46 kg ha-1 γ-PGA could enhance effectively both yield and water use efficiency of soybean in the arid region of northwest China. © 2024 Society of Chemical Industry.

Treatment of Marine Clay Strength Behavior by Demolished Tile Materials and Cement

Known as a problematic soil in the civil engineering field, a sustainable solution to marine clay soil strength behaviour is needed. Another major concern in the engineering field is the solid waste management. Demolished Tile Material (DTM) is one of the largest contributors to construction waste. By utilizing DTM as a stabilizer product to treat marine clay soil, both problems can be minimized. The primary objective of this study is to assess the improvement in marine clay soil's strength characteristics through the addition of DTM and cement. Various proportions of DTM (4%, 8%, 12%, 16%, and 20%) were incorporated into the soil, with a constant 10% cement content. Unconfined Compressive Strength (UCS) measurements were taken at different curing times (0, 7, 14, 28, and 60 days). Results indicate a significant increase in UCS after treating marine clay with DTM and cement, with the most substantial improvement observed at 16% DTM content. The study also emphasizes the role of curing time in enhancing soil strength. The research findings shows that the potential of repurposing DTM for soil stabilization, reducing construction waste, and promoting environmentally responsible construction practices. This study also contributes to the sustainable development of marine clay areas in Malaysia and offers valuable insights for soil engineering and waste management in construction projects.

Characterization of Phosphogypsum for Potential Uses in Soil Stabilization

This research investigated the influence of phosphogypsum (PG) addition to mortar mixture and determined the possibility of utilizing PG in soil stabilization. Originally, the chemical composition and mineralogy of the PG were determined using X-ray fluorescence (XRF) and X-ray diffraction (XRD) tests. The principal constituent of PG becomes calcium sulfate hemihydrate with the presence of some impurities. A total of 9 mixes have been developed: A plain mortar mix is a comparative base, and the other 4 mixes are with 5, 10, 15, and 20 % cement replacement with PG for each type (fresh and stockpiled PG called PGF and PGS, respectively). The experimental program focuses on analyzing the effects of PG on setting time, hardened density, compressive strength, and water expansion of mortar mixtures before its soil stabilization application. Test results indicate that with higher PG, the setting time of the mortar mix is delayed except for the mixture with 20% PG, which experienced an early false set. The results of the compressive strength tests revealed that the 5% PG mixes exhibited higher values compared to the control mix, starting from the 28-day curing period, regardless of PG type. Although the higher PG content and compressive strength lowered, the expansion levels were very low based on the ASTM C 1260 limits for all mixtures, excluding heaving risks.

Potential of Limestone Calcined Clay Cement (LC3) in soil stabilization for application in roads and pavements construction

Clay soil is associated with geotechnical problems of swelling and shrinkage, which causes deformations on structures. Ordinary Portland Cement (OPC) which is the most common stabilizing agent for clay soils, remains unaffordable in most developing countries, and its production also contributes about 8 % of global anthropogenic CO2 emissions. The present study aimed to investigate the effect of Limestone Calcined Clay Cement (LC3) on the stabilization of clay soils for applications in road construction. Clay soil was mixed with quarry dust to reduce the clay content and save cement. The mixture was stabilized using LC3 and OPC separately in proportions of 1 %, 3 % and 5 %. The effect of stabilizer dosage on the performance of clay soil was studied by monitoring the changes in Atterberg limits, Proctor test and soaked California Bearing Ratio (CBR). The mineralogical and microstructural investigation was carried out using X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM) and Thermogravimetric Analysis (TGA). Plasticity index (PI), linear shrinkage (LS), and optimal moisture content (OMC) of stabilized soil was found to decrease with increase in the dosage of LC3 and OPC. The Maximum Dry Density (MDD) and soaked CBR increased with addition of both LC3 and OPC. Formation of calcium silicate hydrate (C-S-H) in both LC3 and OPC stabilized clay soil, as well as formation of Hemi-carboaluminate in LC3 stabilized clay soil was responsible for improved properties of the stabilized soil. The performance of LC3 was found to be comparable to that of OPC, at optimum cement ratio of 5 %.