• Geomechanics and Engineering
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• v.15 no.4
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• pp.957-964
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• 2018

In this study, a method of electrochemical consolidation is applied. This method utilizes electro-osmosis, which is an effective ground improvement technique for soft clays, and soil treatment using lime, which is the oldest traditional soil stabilizer. The mechanism of lime treatment for soil involves cation exchange, which leads to the flocculation and agglomeration. Five representative laboratory tests-an electro-osmotic test and four electrochemical tests with various proportions of lime-were performed on dredged marine clay. The objectives of this study are to investigate the effect of electrochemical treatment and to determine the optimum dose for optimal consolidation performance of dredged marine clay. The results show that a better consolidation effect was achieved in terms of current, temperature, and vane shear strength by using electrochemical treatment. The best results were observed for the electrochemical test using 4% lime content.

• Geomechanics and Engineering
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• v.23 no.2
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• pp.103-113
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• 2020

Gypsiferous soils classified as problematic soils due to the dissolution of gypsum. Presence of gypsum in the soils texture subjected to steady flow can cause serious damages for the buildings, roads and water transmission canals. Therefore, researchers have conducted a series of physical, mechanical and microstructural laboratory tests to study the effect of gypsum leaching on the geotechnical properties of a lean clay containing 0%, 3%, 6%, 9%, 12%, and 15% raw gypsum. In addition, a combination of two nano-chemical stabilizers named Terrasil and Zycobond was used in equal proportions to stabilize the gypsiferous clayey samples. The results indicated that gypsum leaching considerably changed the physical and mechanical properties of gypsiferous soils. Further, adding the combination of Terrasil and Zycobond nano-polymeric stabilizers to the gypsiferous soil led to a remarkable reduction in the settlement drop, compressibility, and electrical conductivity (EC) of the water passing through the specimens, resulting in improving the engineering properties of the soil samples. The X-ray diffraction patterns indicate that stabilization by terrasil and zycobond causes formation of new peaks such as CSH and alteration of pure soil structure by adding raw gypsum. Scanning electron microscope (SEM) images show the denser texture of the soil samples due to chemical stabilization and decrease of Si/Al ratio which indicates by Energy dispersive X-ray (EDS) interpretation, proved the enhance of shear strength in stabilized samples.

• Journal of the Korean GEO-environmental Society
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• v.23 no.1
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• pp.5-13
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• 2022

In tropical regions, lateritic soil is frequently used in road embankment. However, it is one of the sources of road failure owing to its low strength. Generally, cement and lime are used as stabilizers for lateritic soil, but they are not environmentally friendly. Some studies try to use eggshells, for they are food waste and share the same chemical composition as lime. Previous researchs have shown that eggshell powder could enhance the strength of lateritic soil. This research investigated the effect of particle size of the eggshell powder and the effect of the protein-membrane presence in the eggshell on stabilizing capacity of soil. Through laboratory tests, unconfined compressive strength was examined for various particle sizes. The particle size of eggshell powder ranging between 150 ㎛ and 88 ㎛ was appropriate size that made an excellent stabilizer at 3% concentration. On the other hand, the protein-membrane reduced the stabilizing ability of the eggshell powder when the content of eggshell powder is less than 4% in soil. Numerical analysis of road embankment was performed based on the results obtained in the laboratory tests. It is shown that the eggshell powder has improved the stability of the sub-base of the road embankment.

• Journal of the Korean GEO-environmental Society
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• v.15 no.2
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• pp.17-25
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• 2014

In the present study, it were performed an unconfined compression test and a field applicability test according to a mixed ratio of SS, soil type and curing period to analyze strength and deformation characteristic in order to evaluate engineering characteristics of soil mixed pavements using the eco-friendly soil stabilizer (SS). The test results revealed that SS mixed soil shows fast strength development at the initial curing time while 28-day strength amounted for 97% of the final strength. Furthermore, coarse-grained dredged sand (DS) and weathered granitic soil (WGS) have a larger ratio of deformation coefficient with respect to unconfined compressive strength than fine-grained dredged clay (DC) and organic soil (OS). Moreover, a comparison test between natural and forced drying conditions was conducted and test result showed 54% to 67% of strength degradation while having 55% to 63% of strength degradation in the freezing and thawing test result. Finally, a repeated loading test result showed that DS experiences up to 35% of strength reduction compared to initial strength under 10,000 times loading in maximum. Thus, it was validated that an appropriate amount of fine-grained sand is necessary to secure resistance capability to repeated loading.

• Korean Journal of Soil Science and Fertilizer
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• v.38 no.5
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• pp.287-293
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• 2005

In this work, to develop soil inoculant which maintains stable viable cells and normalized quality, studies on micro-encapsulation with bacteria and yeast cells were performed by investigating materials and methods for micro-encapsulation as well as variation and stability of encapsulated cells. Preparation of capsule was conducted by application of extrusion system using micro-nozzle and peristaltic pump. K-carragenan and Na-alginate were selected as best carrier for gelation among K-carageenan, Na-alginate, locust bean gum, cellulose acetate phthalate (CAP), chitosan and gelatin tested. Comparing the gels prepared with Bacillus sp. KSIA-9 and carriers of 1.5% concentration, although viable cell of K-carragenan and Na-alginate was six times higher than those of other, Na-alginate was finally selected as carrier for gelation because it is seven times cheaper than K-carragenan. The gel of 1.5% Na-alginate was also observed to have the best morphology with circular hardness polymatrix and highest viable cell. When investigating the stability of encapsulated cells and the stabilizer effect, free cells were almost dead within 30 or 40 days whereas encapsulated cells decreased in 10% after 30 days and 15-30% even after 120 days. As stabilizer for maintaining viable cell, both 1% starch and zeolite appeared to possess the level of 70-80% cell for bacteria and yeast until after 120 days.

• Geomechanics and Engineering
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• v.12 no.1
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• pp.85-109
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• 2017

The paper presents the laboratory study of clayey soil stabilized with Pond ash (PA), Rice husk ash (RHA), cement and their combination used as stabilizers to develop and evaluate the performance of clayey soil. The effect of stabilizer types and dosage on fresh and mechanical properties is evaluated through compaction tests, unconfined compressive strength tests (UCS) and Split tensile strength tests (STS) performed on raw and stabilized soil. In addition SEM (scanning electron microscopy) and XRD (X-ray diffraction) tests were carried out on certain samples in order to study the surface morphological characteristics and hydraulic compounds, which were formed. Specimens were cured for 7, 14 and 28 days after which they were tested for unconfined compression tests and split tensile strength tests. The moisture and density curves indicate that addition of RHA and pond ash results in an increase in optimum moisture content (OMC) and decrease in maximum dry density (MDD). The replacement of clay with 40% PA, 10% RHA and 4% cement increased the strength (UCS and STS) of overall mix in comparison to the mixes where PA and RHA were used individually with cement. The improvement of 336% and 303% in UCS and STS respectively has been achieved with reference to clay only. Developed stabilized soil mixtures have shown satisfactory strength and can be used for low-cost construction to build road infrastructures.

• Geomechanics and Engineering
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• v.8 no.2
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• pp.173-186
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• 2015

The rapid urbanization in Pakistan is creating a shortage of sustainable construction sites with good soil conditions. Attempts have been made to use rice husk ash (RHA) in concrete industry of Pakistan, however, limited literature is available on its potential to improve local soils. This paper presents an experimental study on engineering properties of low and high plastic cohesive soils blended with 0-20% RHA by dry weight of soil. The decrease in plasticity index and shrinkage ratio indicates a reduction in swell potential of RHA treated cohesive soils which is beneficial for problems related to placing pavements and footings on such soils. It is also observed that the increased formation of pozzolanic products within the pore spaces of soil from physicochemical changes transforms RHA treated soils to a compact mass which decreases both total settlement and rate of settlement. A notable increase in friction angle with increase in RHA up to 16% was also observed in direct shear tests. It is concluded that RHA treatment is a cost-effective and sustainable alternate to deal with problematic local cohesive soils in agro-based developing countries like Pakistan.

• Journal of Applied Biological Chemistry
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• v.65 no.4
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• pp.349-355
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• 2022

In this study, we sought to identify a soil stabilizer that can be applied to paddy fields vulnerable to arsenic (As) pollution. To this end, we conducted a pot experiment in which we evaluated the effects of different stabilizers on the bioavailability of As in paddy soil. As candidate stabilizers, we assessed calcium superphosphate (CSP), sulfur, and steel slag, which were applied at the rates of 0.7 and 1.4, 0.1 and 0.2, and 7.0 and 14.0 Ma ha^-1, respectively. On day 67 after rice transplantation, we detected significantly lower concentrations of As in the solutions of paddy soil treated with 1.4 Ma ha^-1 CSP (96.9 ㎍ L^-1) and 0.2 Ma ha^-1 sulfur (207.2 ㎍ L^-1) compared with the As concentrations in control (314.5 ㎍ L^-1) and steel slag-treated (268.6-342.4 ㎍ L^-1) soil. Compared with the As concentrations in control brown rice (0.16 mg kg^-1), concentrations in brown rice were lowest in the pots treated with 1.4 Ma ha^-1 CSP (0.09 mg kg^-1). Furthermore, in response to CSP treatments, we detected increases in the weight of rice grains (50.0-50.4 g/pot) compared with the control (40.4 g/pot) and other treatments (26.9-48.1 g/pot), which we speculate could be attributed to the reduction in As toxicity to rice owing to a decline in soil solution As contents and the fertilization effect of the CSP treatment. Collectively, our findings indicate a high-level application of CSP (1.4 Ma ha^-1) to paddy soil has a comparatively beneficial effect in mitigating the bioavailability of As.

• Journal of Soil and Groundwater Environment
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• v.26 no.6
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• pp.65-73
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• 2021

Since the amount of red mud, generated from aluminum smelting process as a by-product, has increased worldwide, the recycle and metal resource recovery from the red mud is becoming more important. In this study, in order to recycle the red mud as a soil stabilizer to remediate arsenic contaminated soils, neutralization of red mud was investigated. Red mud was neutralized by washing with distilled water and NaCl, CaCl₂, FeCl₃, and HCl solutions and heating at 200-800℃, and arsenic stabilization characteristics in soils were evaluated with the neutralized red mud. Although washing with distilled water was not effective in neutralizing red mud, the application of the washed red mud to soils lowered the soil pH compared to the application of untreated red mud. Among NaCl, CaCl₂, FeCl₃, and HCl solutions, washing with FeCl₃ showed the most effective in lowering pH of the red mud from pH 10.73 to pH 4.26. Application of the neutralized red mud in soils resulted in quite different arsenic stabilization efficiency depending on soil samples. In M1 soil, which showed relatively high arsenic stabilization efficiency by untreated red mud, the neutralization of red mud resulted in little effect on arsenic stabilization in soil. On the other hand, in M2 soil, which showed low arsenic stabilization efficiency by untreated red mud, the neutralization of red mud increased arsenic stabilization significantly. Soil characteristics such as clay minerals and pH buffering capacity seemed to affect reactions between red mud and soils, which resulted in different effects of the red mud application on soil pH and arsenic stabilization efficiencies.

• Tunnel and Underground Space
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• v.25 no.6
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• pp.505-514
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• 2015

In this study, a stabilizing equipment was developed to resolve the problems of existing stabilization construction method for contaminated soil. The field application and workability of the stabilizing equipment were verified through field demonstration tests and laboratory tests. The field application of the stabilizing equipment was identified through field demonstration tests. As a result of laboratory tests for field mixed soil, the mixing capability of stabilizer of the developed construction method was better than that of existing construction method.