Dispersive saline soil is a type of water sensitive special soil with the characteristic of instability when encountering water, and its engineering properties are unstable. Therefore, this research proposes the use of environmentally friendly biopolymer guar gum to improve soil dispersivity and explores the feasibility of guar gum in improvement of dispersive saline soil. The mechanical properties of the improved dispersive saline soil were determined through unconfined compressive strength tests and direct shear tests. The influence of guar gum on the dispersivity and physical properties of the soil were investigated by crumb tests, pinhole tests, liquid plastic limit tests and particle size distribution tests. The microstructure and mineral composition of the improved soil were analyzed by X-ray diffraction, Fourier transform infrared spectroscopy, and scanning electron microscopy tests. Experimental results indicate that 1.5 % guar gum can transform highly dispersive soil into non-dispersive soil after curing 28 days. When the guar gum content increases from 0 % to 4 %, the unconfined compressive strength increases by 81.30 %, and the cohesion and internal friction angle increase by 117.02 % and 32.69 %, respectively. Guar gum is enriched with hydroxyl groups, which form hydrogels in contact with water, and form a cationic bridge with the surface cations of clay particles, the two aspects work together to cement the soil particles, dense soil structure. Guar gum can effectively improve the dispersivity and mechanical properties of dispersive saline soil, and can be used as an environmentally friendly soil modification material.

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.

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 a common problem soil in engineering projects, which has the potential risk of causing serious engineering failures. In this paper, calcined waste phosphorus slag (CPS) was chosen to enhance the mechanical properties and reduce soil dispersivity. Dispersive soil samples with 1 % to 10 % CPS content were prepared and cured for 0 to 28 days. The dispersivity identification test was used to assess soil sample dispersivity. The compressive and tensile strength, conductivity, and pH were determined for the soil. Microstructural and mineral composition were analyzed using SEM/EDS, TG/DTG, and XRD analysis. The natural dispersive soil was selected to verify the effect of CPS in improving soil. Experiments show that the CPS inhibits soil dispersivity and converts it into non-dispersive soil. Both compressive and tensile strength increases significantly with the increase in the content of CPS and curing time. The tensile strength of the soil samples cured for 28 days increased by about 76 % and the compressive strength by about 61 % as the mixed content of CPS was increased from 1 % to 10 %. Results show that CPS can improve the strength and modify the dispersivity of soil, its optimal mixing content is 5 %. In addition, using CPS in dispersive soil could also solve the disposal problem of phosphate slag, which is a win-to-win solution. (c) 2024 Production and hosting by Elsevier B.V. on behalf of The Japanese Geotechnical Society. This is an open access article under the CC BY- NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

Dispersive soils are frequently employed as construction materials in projects such as drains and dams in western Jilin, China. However, their propensity to disperse upon contact with water presents a grave threat to construction projects if left unaddressed. Therefore, following the identification of the fundamental physical and chemical properties, as well as the dispersivity of soils in the western region of Jilin Province, Sporosarcina pasteurii was chosen to conduct laboratory experiments and mechanistic studies aimed at improving dispersive soils in the area through MICP. The treatment effect of the soil samples was quantitatively assessed through tests including comprehensive dispersivity identification, unconfined compressive strength (UCS) measurement, and determination of calcium carbonate content. Furthermore, scanning electron microscope (SEM) tests were conducted to examine the microstructural alterations of the soil samples before and after microbial treatment. The experimental results showed that soil dispersion can be significantly reduced under various conditions, and increase the soil strength under certain condition. MICP facilitates the replacement of exchangeable Na+ in soil and induces the formation of calcium carbonate, which fills pores and acts as a cementing agent. Treating dispersive soil in western Jilin is crucial to ensuring the safe and normal operation of its water conservancy projects.

Dispersivity is a severe pathology that occurs mainly in clay soils and is usually catastrophic in geotechnical structures susceptible to this damage. Hundreds of dams worldwide have failed due to quality problems, mainly by piping in the body, foundation, spillway, culvert, and other peripheral structures. The pinhole test is currently considered the most accurate test for detecting the dispersivity of clay soils. However, it presents problems when objectively evaluating the dispersivity of a material due to the qualitative nature of the estimation of results. In particular, the methodology for determining turbidity has been identified. This document studies different piping paths in the sample, which a priori may be more realistic than the single path in the current test. A kaolinitic clay, widely studied through index and mineralogical tests, is used as the base material. Regarding the detection of dispersivity, a specialized test package was used to reduce the uncertainty of the results. Natural samples were analyzed using ASTM D4647-13. A modification of the pinhole test was proposed based on the imposition of additional artificial channels. The results revealed that this modification can make the test more realistic because when the dispersive front advances in the soil, it does not travel along a single path but instead looks for different erosive paths. The details of this assertion are discussed throughout the paper.

Dispersive soil is a widely distributed problematic soil in arid or semiarid areas of the world and can cause pipe erosion, gully damage and other seepage failures. This study analyzed the effect of environmentally friendly enzyme-induced carbonate precipitation (EICP) on the dispersivity of dispersive soils. This methodology was tested for the stabilization of three dispersive soil types (two high-sodium soils, two low-clay-content soils, and two soils with both high sodium and low clay contents) to examine the impact on dispersivity based on the results of pinhole tests and mud ball tests. Physical, chemical, mechanical, and microscopic tests were also conducted to investigate the effects of the components in the EICP reaction solution on dispersive soil modification. The experiments showed that the concentration of the reaction solution and the curing time required to limit the dispersivity decreased with increasing clay content in the soil. Ca2+ limited the dispersivities of dispersive soils via four distinct mechanisms. The first mechanism was ion exchange; Ca2+ decreased the percentage of exchangeable sodium ions to less than 7% while reducing the thickness of the diffuse double layer such that the spacings between soil particles were reduced and the chemical dispersivity was limited. Second, Ca2+ increased the viscosity of the solution by salting out the organic matter present in the soybean urease. Subsequently, the D1-class physically dispersive soil was converted into an ND2-class nondispersive soil. Third, Ca2+ decreased the soil pH by reducing the CO32- content, which could hydrolyze to increase the soil alkalinity. Finally, the presence of Ca2+ led to the generation of cementitious minerals through the precipitation of CaCO3 crystals that continuously generated CO32-, filling and cementing soil particles and thereby limiting their physical dispersivity. These results indicated that a low-concentration EICP reaction solution efficiently controlled the dispersivities of the three dispersive soils.

Dispersivity has long been a major concern in civil and geo-environmental engineering, as well as in agricultural engineering and soil sciences. Dispersive clay soils are common, but their prevalence and characteristics vary greatly across different regions of the world, especially in arid and semi-arid areas. These soils are highly unstable and prone to erosion when exposed to water, due to their high concentration of exchangeable sodium ions and large specific surfaces. This can cause serious damage to hydraulic infrastructure. However, identifying and stabilizing dispersive clay soils is crucial for infrastructure projects, as the use of untreated soils can result in irreversible and catastrophic failures due to internal erosion and piping. The systematic management of dispersive clays is crucial to prevent the wastage of fertile agricultural land and land designated for engineering construction. Although industrialization has numerous benefits, it often results in large quantities of waste byproducts that must be managed appropriately to reduce their environmental impact. The reuse of these wastes in soil improvement has become an increasingly popular approach to address both environmental pollution and cost-effectiveness concerns. Despite the growing interest in using waste by-products for soil stabilization, there is a lack of a systematic and comprehensive review of the management, mechanisms, identification systems, and improvement strategies for both traditional and non-traditional stabilizers. Therefore, there is an urgent need to review the available literature to provide a comprehensive understanding of the use of waste by-products for soil stabilization. Such a review could aid in the creation of soil stabilization methods that are both efficient and enduring while minimizing the environmental impact of waste by-products.

The engineering problems caused by dispersive soil are of worldwide concern. Traditional high carbon emission soil amendments such as cement and lime cause several environmental problems, including pollution and soil alkalization. Inorganic polymers are considered to be an economical, effective, and environmentally friendly soil amendment. Therefore, this paper proposes the use of the polymeric coagulant polyaluminum chloride (PAC) to improve soil dispersivity. PAC was added to the dispersive soils at different dry mass ratios of 0%, 0.5%, 1%, 1.5%, 2.5%, 4%, 5%, 6%, 7%, 8%, and 10%. The soil samples were then cured for 1, 4, 7, 14, and 28 days. Soil dispersivity was determined by crumb tests, pinhole tests, and exchangeable sodium ion percentage tests. Soil mechanical strength was assessed through unconfined compressive strength tests and unconsolidated undrained triaxial tests. Particle size distribution, pH, resistivity, X-ray diffraction, Fourier transform infrared spectroscopy, and scanning electron microscopy tests were conducted to investigate soil improvement mechanisms. Experimental results indicate that 1.5% PAC can transform highly dispersive soil into non-dispersive soil after 1 day of curing. When the PAC content increases from 0% to 7%, the unconfined compressive strength of the soil increases by 110.1%, and the internal friction angle and cohesion increase by 61.1% and 24.2%, respectively. The changes in the physicochemical properties and microstructure of the soil indicate the high-valence cations produced by PAC hydrolysis can effectively replace Na+ in the soil, while significantly reducing the pH value of the soil. Simultaneously, the coagulation effect generated markedly reduces soil porosity, resulting in a more compact soil structure. In summary, PAC demonstrates excellent potential in improving soil dispersivity and mechanical properties. Compared to traditional high carbon emission amendments such as cement and lime, PAC can effectively reduce soil alkalinity, mitigate environmental issues associated with these materials, and offer new possibilities for improving dispersive soils.

This paper investigated the improvement behaviors on dispersivity, water stability and mechanical properties of dispersive soil by calcined coal gangue (CCG) at 700 degrees C, and analyzed the modification mechanism. Dispersive soil specimens with different content of CCG (varying from 1 % to 10 %) were prepared and cured for 0-28 days. The dispersivity of the soil was determined by three different dispersivity determination tests. The tensile strength and compressive strength of the dispersive soil were determined by mechanical property tests. SEM, EDS, TG and XRD analytical methods were employed to reveal microstructure and mineral changes during modification. The results of the study show that the admixture of CCG and the prolongation of curing time contributed favorably to suppressing the dispersivity of the soil and enhancing the water stability, the compressive strength and tensile strength of the dispersive soil. With the increasing of CCG content and the prolongation of curing time, the dispersive soil gradually transforms into non-dispersive soil. Microstructural and mineral analysis indicate that CCG has pozzolanic activity, and the production of pozzolanic reaction products significantly increase the friction and cohesion among soil particles. The results show that the utilization of CCG as an admixture to improve the dispersive soil not only solves the disposal problem of waste gangue, but also optimizes the undesirable characteristics of the dispersive soil. And the modification effect of CCG on dispersive soil in practical engineering is confirmed by validation test.