Dispersive soils, due to their high erodibility and cation exchange sensitivity, pose significant challenges in geotechnical applications. This study investigates the engineering behavior of such soils under a wide range of thermal regimes (25-900 degrees C), focusing on their mechanical, hydraulic, and physicochemical properties. Unlike previous studies that emphasized microstructure alone, this research integrates a broad range of analytical methodsmineralogical (XRD, SEM), chemical (CEC, SSA, carbonate content), and geotechnical (Atterberg limits, unconfined compressive strength, permeability, TGA) to capture a comprehensive understanding of thermal stabilization effects. Results reveal that thermal treatment significantly enhances soil performance: at 300 degrees C, dispersion decreased by 65% due to complete free water removal; at 500 degrees C, dehydroxylation induced structural rearrangement and mineral breakdown, improving both strength and permeability. At 700 degrees C and beyond, the formation of cementitious phases such as gehlenite and anorthite transforms the soil into a dense, non-dispersive medium, increasing UCS by 36.5 times and permeability by 12,000 times. These findings emphasize the effectiveness of high-temperature treatment as a sustainable and technically sound approach for stabilizing dispersive soils in geotechnical and environmental applications, including landfill liners, geothermal barriers, and contaminant containment zones.

The enzyme-induced calcium carbonate precipitation (EICP) method has been utilized for curing low-permeability clay by directly mixing the reaction solution with soil. The added reaction solution quantity is limited by the optimal water content, producing insufficient calcium carbonate. Herein, the high-activity urease and high-concentration cementation solution efficacy in treating dispersive soils was evaluated. Phase transitions and structural modifications in EICP-cured soils were investigated through oscillatory amplitude scanning. The soil gradation influence on the EICP treatment effectiveness was assessed. The fluidized EICP-cured soil cementation and rupture mechanisms were investigated by viscosity measurements, electron microscopy, and zeta potential evaluations. A 3 M cementation solution, coupled with 500g/L of soybean urease, significantly enhanced the soil shear resistance, increasing it by 339% to 1807%. The EICP-cured soil gradually transitioned from a fluid to a paste and eventually to a solid within 168 h. High-clay-particle-content soils exhibited pronounced increases in shear resistance after EICP treatment. Under dynamic loading, three shear crack types emerged in EICP-cured soils, emphasizing the importance of soybean protein viscosity and calcium carbonate crystal filling-bonding capability in enhancing soil structural stability. The fluid solidification effectiveness in treating fine-grained soils utilizing EICP was validated through erosion trenches in fluid-solidified check dams, validating its potential.

The low chemical reactivity of bauxite residue (BR) has significantly limited its effective utilization, leading to widespread disposal and severe environmental pollution. In semi-arid regions, dispersive soils threaten the stability of silt retention dams, which are vital for controlling erosion. To enhance the utilization of BR and mitigate the dispersibility of dispersive soil, this study employed thermal activated BR to treat both artificially prepared and natural dispersive soils. The stabilizing effects of thermal activated BR on dispersive soil were evaluated using dispersibility identification tests, mechanical tests, and particle size analyses. The stabilization mechanisms were further examined through chemical, microscopic, and mineralogical tests. Results indicate that incorporating 2 % thermal activated BR effectively controls the dispersibility of both dispersive soils, increasing their unconfined compressive strength (UCS) and Brazilian tensile strength (BTS) by up to 426 % and 167 %, respectively. During the initial reaction period (0-3 days), the abundant calcium and aluminum ions precipitated by the BR rapidly reduce the thickness of the water film around the clay particles, while the BR powder fills the voids between soil particles. As the reaction progresses, hydroxide ions are continuously released, peaking at 7 days (pH 11.33), triggering a vigorous carbonation reaction. The resulting calcium carbonate fills and cements the soil particles. In the later stages of the reaction (14-28 days), carbonation and hydration reactions occur simultaneously, binding numerous particles <= 0.075 mm into sand-sized particles, thereby significantly enhancing the soil strength and water stability. The validation tests of naturally dispersive soils in this study provide guidance for the resource utilization of BRs and the improvement of dispersive soils.

The modification of dispersive soils remains a prominent and challenging issue in the field of geotechnical engineering. Using lime, fly ash, and CaCl2 as benchmark materials, this study explores the potential of enzymeinduced calcite precipitation (EICP) technology to modify three kinds of dispersive soils. The modification effects of the four materials were systematically evaluated through crumb and pinhole tests. By linking the modification performance to curing time and material dosage, the study proposes a novel formula to compare the modification efficiency of the materials. To enhance practical applicability in engineering contexts, the study also investigates the impact of these materials on the mechanical properties of dispersive soils through unconfined compressive strength (UCS) tests. Furthermore, the modification mechanisms of the materials were compared using exchangeable sodium percentage (ESP) analysis, scanning electron microscopy (SEM), Energy Dispersive Spectrometer (EDS), and X-ray diffraction (XRD). The results indicate that both EICP technology and lime exhibit superior modification effects, effectively enhancing the resistance to water erosion and the mechanical properties of dispersive soils. Compared to lime, EICP technology demonstrates higher modification efficiency and greater environmental sustainability. Notably, low-concentration EICP solutions can effectively modify all three kinds of dispersive soils tested in this study.

The existence of dispersive clay soils can cause serious erosion, void, and structural damage due to an imbalance of the electrochemical forces within the particles, which causes the soil particles to be repulsive instead of being attracted to each other. Dispersivity is observed in several highway embankments in Mississippi, and the embankments have eroded and developed voids over time. The current study investigated the root cause of the voids observed within the subgrade of the state highway 477 in Mississippi and evaluated the dispersivity of high cations-based soil. As part of an investigative initiative, a 2D Ground Penetration Radar (GPR) of the highway embankment road to make a 2D profile of the soil subsurface media was surveyed to reveal that potential hotspots were overlooked, leading to suspected soil dispersivity and subsequent issues. To assess the extent of visible voids and sinkholes, dispersive tests, including the Double Hydrometer Test (DHT), were conducted to evaluate the dispersivity of the clay soils. A series of boreholes were drilled along the roadway to collect the soil samples, determine their physical properties, and identify clay soil dispersity within the soil profile. Following the confirmation of dispersive soil existence through these tests, advanced analyses, such as Scanning Electron Microscope (SEM) to identify the microstructures and the ionic compositions of the soil particles and Toxicity Characteristic Leaching Procedure Tests (TCLPT) to assess the solubility of high concentrated elements in liquid, were performed to comprehend the root cause of the soil dispersion. Based on the results of the analysis, the GPR wave cannot pass through the subgrade, which mostly happens due to the presence of the charge within the soil. Based on SEM, DHT, and TCLP test results, the soil samples have high cations, including the presence of K + . Moreover, a similar distribution of the ionic compositions was observed among the majority of the soil samples; however, the percent of dispersion regarding clay soil particles varied.

This study addresses the challenges posed by dispersive soil in various engineering fields, including hydraulic and agricultural engineering, by exploring the effects of physical adsorption on soil modification. The primary objective is to identify an environmentally friendly stabilizer that can alleviate cracking and erosion resulting from soil dispersivity. Activated carbon (AC), known for its porous nature, was examined for its potential to enhance soil strength and erosion resistance. The charge neutralization process was evaluated by monitoring pH and conductivity, in addition to a comprehensive analysis of microscopic and mineral properties. The results show that high sodium levels or low clay contents result in the dispersive nature of soil in water. However, the incorporation of AC can transform such soil into a non-dispersive state. Moreover, both soil strength and erosion resistance exhibited enhancements with increasing AC content and curing duration. The incorporation of AC resulted in a maximum 5.6-fold increase in unconfined compressive strength and a 1.8-fold increase in tensile strength for dispersive soil. Notably, a significant correlation was observed during the curing phase among soil dispersivity, mechanical properties, and pH values. Microscopic analyses revealed that the porous structure of AC facilitated a filling effect and enhanced adsorption capacity, which contributed to improved soil characteristics and reduced dispersivity. The release of hydrogen ions and the formation of aggregates promote water stability. Validation tests conducted on dispersive soil from northern Shaanxi demonstrated the efficacy of physical adsorption using AC as a viable method for modifying dispersive soil in the water conservancy hub. (c) 2025 Institute of Rock and Soil Mechanics, Chinese Academy of Sciences. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/ 4.0/).

Dispersive soil is highly susceptible to water erosion, leading to significant engineering challenges, such as slope instability and canal damage. Common modifiers such as lime are effective but cause environmental pollution. Therefore, it is important to explore eco-friendly modifiers. This study investigates the effects of sticky rice and calcium chloride (SRC) on dispersive soil. Dispersivity tests identified an optimal ratio of sticky rice to calcium chloride of 3:1. To analyze the effects of different SRC contents and curing times on the soil properties, tests of dispersivity, hydraulic, mechanical, chemical, and microscopic mechanisms were conducted based on this optimal ratio. The results indicated that 1.5% SRC effectively eliminated soil dispersivity even without curing, and its effectiveness improved with an extended curing time. After 28 days of curing, the water stability increased significantly, permeability decreased by an order of magnitude, and cohesion improved by approximately 85.97%. SRC reduced soil dispersivity through three primary mechanisms: lowering the pH, promoting ion exchange between Ca2+ and Na+, and the cementing effect of the sticky rice paste. Additionally, Ca2+ acted as a bridge between organic colloids and clay particles, further strengthening the structural stability of microaggregates. Overall, SRC proved to be an effective eco-friendly modifier for improving physicochemically dispersive soil.

Dispersive soil has poor engineering geological properties, which can lead to various geological hazards in practical engineering projects. This study utilizes guar gum, an eco-friendly biopolymer with great potential in soil improvement, to improve dispersive soils in western Jilin. Guar gum powder was added to the dispersive soil at dry mass ratios of 0%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 4%, and 5%, and cured for 1, 3, 7, 14, and 28 days. The improvement effect was comprehensively evaluated by dispersion identification test, unconfined compressive strength test before and after immersion, disintegration test, matric suction test, and permeability test. The mechanism of guar gum in improving dispersive soil was further explained from the microscopic point of view by particle size analysis, scanning electron microscopy (SEM) and X-ray diffraction (XRD). The results showed that more than 1.5% guar gum proportion was effective in eliminating soil dispersion. The cured soil had the best mechanical properties at 3.0% guar gum content. With the incorporation of guar gum, the hydrophysical properties of the soil were also improved. Guar gum wraps around soil particles, forming bridges through the hydrogel. Additionally, it fills the voids in the soil, leading to a denser aggregation of the soil particles. In conclusion, guar gum, as an environmentally friendly biopolymer, has a positive effect on the improvement of dispersive soils. The research results will provide theoretical guidance for engineering construction in dispersive soil areas.

This study investigates the influence of four soil improvement methods-microbially induced carbonate precipitation (MICP), electrokinetics (EK), chemical additives, and a combination of EK and chemical additives-on the dispersivity, mechanical properties, and microstructure of dispersive soil. A series of tests was designed to evaluate the effectiveness of these methods on dispersive soil. Both the original and treated soil samples were tested to assess changes in soil properties, including dispersivity, plasticity, pH, unconfined compressive strength (UCS), shear strength, and microstructure. Dispersivity was assessed using pinhole tests, crumb tests, double hydrometer tests, and exchangeable sodium percentage tests. The experimental results indicate that the combined EK and chemical additives method significantly reduces the dispersivity and plasticity of the dispersive soil compared with the other methods, leading to improved UCS. The EK and chemical additive methods individually demonstrate effective modification under a voltage of 48V and an additive content of 4%, respectively, enhancing the shear strength of the dispersive soil. MICP does not significantly improve the dispersivity of dispersive soil, but it does enhance the shear strength of the treated soil, with a particularly notable increase in the internal friction angle. Overall, the combined method shows more remarkable improvements in the dispersive soil than any single method. In summary, the combination of EK and chemical additives has significant potential for improving the dispersivity and mechanical properties of dispersive soil.

Dispersive soil is susceptible to water erosion and could cause damage in geotechnical engineering or hydraulic engineering projects. Recycled clay brick powder (RCBP) was used as a modifier to improve the dispersivity and water stability of dispersive soil in this study. Pinhole tests, crumb tests, disintegration tests, particle analysis tests, exchangeable sodium percentage (ESP) tests, pH tests, conductivity tests, and X-ray diffraction (XRD) and scanning electron microscopy (SEM) analyses were conducted to explore the modification effects and corresponding mechanisms of RCBP on dispersive soil. The results revealed that the dispersivity of the soil significantly weakened as the RCBP content increased and curing time extended. Specifically, adding 4% RCBP to the soil and curing for 7 days effectively transformed dispersive soil into nondispersive soil. Furthermore, the final disintegration time of the soil sample with 10% RCBP cured for 28 days was 273% longer than that of the soil sample without curing. Moreover, the treatment led to decreased fines content, ESP value, and pH value in the soil samples. The decrease in ESP value indicated the replacement of sodium ions adsorbed on the soil particle surfaces with calcium ions, resulting in a reduction in the thickness of the diffuse electric double layer of soil particles, and subsequently reduced soil dispersivity. Additionally, the decrease in pH also contributed to the reduction of the diffuse electric double-layer thickness. XRD and SEM analyses confirmed the formation of cementing materials between soil particles due to the modification, which filled gaps and cemented particles to create a waterproof barrier between soil particles. In conclusion, the utilization of RCBP as a modifier for dispersive soil could be a win-win measure with promising outcomes. It is recommended that more than 4% RCBP should be added in engineering applications.