• KSCE Journal of Civil and Environmental Engineering Research
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• v.35 no.5
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• pp.1083-1096
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• 2015

This study utilised Computational Fluid Dynamics(CFD) for preliminary assessment of mixing efficiencies of 2-phase fluids in a pipe at which a slurry flow and an injected solidifier join, for the purposes of reducing trial-and-error-based instances of physical experiments and conducting the overall research in an economical way. Using OpenFOAM$^{(R)}$, we simulated behavior of 3-phase fluids under 18 different settings generated by changing diameters of a dredged soil transportation pipe, a quality improving material injection pipe and the confluence angle. While difference in mixing efficiencies amongst the instances was insignificant, discernible boundary layers amongst the materials were observed in all of the instances. In order to break the boundary layers, we designed a substructure inside a pipe and found out that it could remarkably improve mixing efficiencies particularly for short distance applications.

• Journal of the Korea Organic Resources Recycling Association
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• v.18 no.3
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• pp.68-76
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• 2010

In the green house, the effect of the mixed material of vermicast and humic acid on the growth of young raddish was investigated. 5, 10, 15, 30 or 50 kg(a.i.) of solid type humic acid was mixed with 300kg(d.w.) of vermicast/10a, each of which was applicated to the soil. And the conventional treatment(600kg of conventional organic fertilizer/10a) and untreatment plot were rendered for comparison. In all the experimental plots treated with vermicast, the number of leaves, leaf length, leaf biomass, root length, root diameter, root biomass of young raddish were higher than those in untreated plot. And in the experimental plots treated with the mixed materials of vermicast and humic acid, growth rate of young raddish was equal to or higher than that in the conventionally treated plot. Fresh biomass of leaves per leol' raddish in the plot treated with 300kg of vermicast + 5kg of humic acid was 1.79 times higher than that in the untreated plot and fresh biomass of root was 2.08 times higher, which was much more effective in its growth rate than that in any other treated plots. There were no prominent changes in soil physicochemical properties after the leol' raddish harvest from the soil treated with vermicast and humic acid, though.

• International Journal of Highway Engineering
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• v.7 no.1 s.23
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• pp.39-47
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• 2005

Fiber reinforced soils have recently implemented to fills and base layers of highways and railroads, and deformation behaviors of reinforced soils in turn should be investigated. The paper evaluated deformation characteristics of fiber reinforced sands and their effectiveness of reinforcement using resonant column tests. The specimens were prepared by varying gradation and mixing polypropylene staple fibers of 0.3% fiber content. Maximum shear moduli of reinforced sands were increased by up to 30% with increasing uniformity coefficient. Shear moduli of well-graded reinforced sands were larger than those of poorly-graded ones regardless of confining pressure in the whole range of shearing strain and reinforcement was, in turn, more effective with higher uniformity coefficient.

• Journal of the Korean GEO-environmental Society
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• v.14 no.10
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• pp.39-47
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• 2013

Recently, there have been various domestic construction activities related to the reclamation of the dredged soils to expand the land use. However, the reclaimed grounds made of the dredged soils cause various problems due to highly compressible and low shear strength nature. Particularly, this nature induces huge problems in case of the harbor facilities and road construction on the reclaimed sites. Furthermore, in the reclamation activities, the marine dredged soils are often used instead of the well sorted sand, which induces problems of compressibilities. Therefore, in this study, the mechanical characteristics of artificial soil mixture of kaolinite representing the marine dredged soils and the pond ash. A large consolidometer is designed and manufactured to produce the artificial soil mixture. To represent various mixing ratio between the fly ash and bottom ash in the pond ash, six samples with the same stress history are made with different mixing ratio among kaolinite, bottom ash and fly ash. Isotropically consolidated and undrained compression tests are performed to investigate the shear characteristics of soil mixtures. Based on the experimental results, as the components of mixed ash increase, the friction angle increase and the cohesion values decrease. Also, the porepressure parameters at failure, Af increase with the mixing components of the pond ash. The portion of bottom ash has more impact on the shear behavior than that of fly ash.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.5C
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• pp.303-312
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• 2006

This study is to evaluate the mechanical characteristics of flowable backfill and offer a guide line of mixture proportion based on soil types for constructing underground power utilities. Flowable backfill is known as soil-cement slurry, void fill, and controlled low-strength material(CLSM). The benefits of CLSM are reduced equipment costs, faster construction, re-excavation in the future, and the ability to place materials in confined spaces, which are narrow parts or perimeters of underground power cables nearly impossible for compaction. The flowable slurry mixed with 17 soils and 6 accelerated mixtures in the laboratory were evaluated for flowability and unconfined compressive strength to meet the target values of this study.

• Journal of the Korean GEO-environmental Society
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• v.15 no.10
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• pp.29-34
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• 2014

In order to examine strength properties depended on climate changes of solidified soil amended by porosity silica which enhance harms of cement, this study conducts a wetting and drying repetition test and then, attempts to verify strength properties before and after solidified soil gets environmental influence. Test pieces for the unconfined compression test changed the mixing ratio of solidified soil compared to mixed soil weigh to 5 %, 10 % and 15 %. For each step, it was created by mixing 0.5 %, 1.0 % and 1.5 % of wood chips, and curing period for 7, 14, and 28 days. Then, the wetting and drying repetition process was repeated 0, 3, 6, and 12 cycles to analyze mechanical properties. To also evaluate changes of relative dynamic elastic modulus before and after the wetting and drying, dynamic elastic modulus tests were conducted when each cycle was completed.

• Journal of the Korean GEO-environmental Society
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• v.11 no.10
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• pp.15-24
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• 2010

In the case of underground power utilities pipe such as circular pipe, the most difficult problem is low compaction efficiency of the bottom of pipe inducing the failure of utilities. To overcome this problem, various studies have been performed and one of these is CLSM(Controlled Low Strength Materials) accelerated flow ability. But underground power utilities pipe backfill materials is also needed to have good thermal property that can dissipate the heat as rapidly as it is generated. So, in this study, we performed thermal resistancy test for various materials such as sand, weathered soil, clay and mixed soil to analyze the thermal characteristics of CLSM(Controlled Low Strength Materials) with accelerated flow ability for various conditions(water content, unit weight, void ratio, curing time) and to evaluate the applicability for backfill material of underground power utilities pipe. The test results of 16 specimens for thermal resistancy test showed good thermal property that maintained below $85^{\circ}C\;cm/W$.

• Journal of the Korean Geotechnical Society
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• v.18 no.5
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• pp.19-25
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• 2002

In this paper, a laboratory investigation was carried out to change the geotechnical properties of clayey soil with quicklime and rice husk ash for surplus soil strength improvement. The organic content of soils is 8.67%, 6.45% and 3.84% respectively. The geotechnical properties of treated soil were evaluated by a series of laboratory unconfined compression test, consolidation test and etc. The test results indicated that the presence of RHA enhanced the efficiency of lime stabilization. Especially, the increase in strength is very high at the first stage, while the significant improvement occurs in a sample C with organic content of 3.84%. These results can be identified by X-ray diffraction(XRD) and scanning electron microscope(SEM). The results of consolidation test indicate that the presence of RHA with lime reduces the properties of swelling of soil. Thus, it was verified that the addition of RHA is more effective than using only lime for soil stabilization.

• Journal of the Mineralogical Society of Korea
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• v.6 no.1
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• pp.17-26
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• 1993

Mineralogical characteristics of tosudite from the Sungsan and Bubson mines were studied and correlated using X-ray diffraction analysis, chemical analysis and electron microscopy. Tosudite occurs as an alteration product of Cretaceous volcanoclastic rocks in both mines. It is associated with microcrystalline quartz, dickite, illite/smectite or mica/smectite mixed-layer mineral. It forms cryptocrystalline aggregates with flaky habit. XRD analysis suggests that tosudite is an 1:1regularly interstratified dioctahedral smetite/dioctahedral chlorite. Bubsoo tosudite has more(00ℓ ) reflections and more periodice stacking sequence than Syngsan tosudite. Chemical analysis shows that tosudite is a Li-bearing aluminous 1:1 regularly interstrattified mineral composed of K-bedellite and donbassite. Cookeite component may be present in the chlorite layer. Bubsoo tosudite is more Al in tetrahedral site and Ca in interlayer, but less Al in octahedral site than Sugsan tosudite. Tosudite may be formed as the intermediate alteration products, forming after muscovite and before illite/smectite or mica/s$^{\circ}C$mectite, with the range from 100 $^{\circ}C$ to 360 ~ 480 $^{\circ}C$. The hydrothermal solution forming tosudite may be acidic solution with high activities of Si and Al.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.29 no.5C
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• pp.207-215
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• 2009

Cemented soils or concrete are usually cured under moisture conditions and their strength increases with curing time. An insufficient supply of water to cemented soils can contribute to hydration process during curing, which results in the variation of bonding strength of cemented soils. In this study, by the consideration of in situ water supply conditions, cemented sand with cement ratio less than 20% is prepared by air dry, wrapped, moisture, and underwater conditions. A series of unconfined compression tests are carried out to evaluate the effect of curing conditions on the strength of cemented soils. The strength of air dry curing specimen is higher than those of moisture and wrapped cured specimens when cement ratio is less than 10%, whereas it is lower when cement ratio is greater than 10%. Regardless of cement ratio, air dry cured specimens are stronger than underwater cured specimens. A strength increase ratio with cement ratio is calculated based on the strength of 4% cemented specimen. The strength increase ratio of air dry cured specimen is lowest and that of wrapped, moisture, and underwater cured ones increased by square. Strength of air dry cured specimen drops to maximum 30% after wetting when cement ratio is low. However, regardless of cement ratio, strength of moisture and wrapped specimens drops to an average 10% after wetting. The results of this study can predict the strength variation of cemented sand depending on water supply conditions and wetting in the field, which can guarantee the safety of geotechnical structures such as dam.