• Title/Summary/Keyword: Granular soils

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Shear Strength Estimation of Clean Sands via Shear Wave Velocity (전단파 속도를 통한 모래의 전단강도 예측)

  • Yoo, Jin-Kwon;Park, Duhee
    • Journal of the Korean Geotechnical Society
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    • v.31 no.9
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    • pp.17-27
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    • 2015
  • We perform a series of experimental tests to evaluate whether the shear strength of clean sands can be reliably predicted from shear wave velocity. Isotropic drained triaxial tests on clean sands reconstituted at different relative densities are performed to measure the shear strength and bender elements are used to measure the shear wave velocity. Laboratory tests reveal that a correlation between shear wave velocity, void ratio, and confining pressure can be made. The correlation can be used to determine the void ratio from measured shear wave velocity, from which the shear strength is predicted. We also show that a unique relationship exists between maximum shear modulus and effective axial stress at failure. The accuracy of the equation can be enhanced by including the normalized confining pressure in the equation. Comparisons between measured and predicted effective friction angle demonstrate that the proposed equation can accurately predict the internal friction angle of granular soils, accounting for the effect of the relative density, from shear wave velocity.

Effect of Repeated Application of IBP on the Degradation of Pesticides in Flooded Soil (IBP의 반복처리(反復處理)가 담수토양중(湛水土壤中) 농약(農藥)의 분해(分解)에 미치는 영향(影響))

  • Song, Byeong-Hun;Jeong, Young-Ho;Park, Young-Sun
    • Korean Journal of Environmental Agriculture
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    • v.1 no.1
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    • pp.65-70
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    • 1982
  • This experiment was conducted to see the effect of repeated application of IBP granular formulation(17%, 0,0-diisopropyl-S-benzyl thiophosphate) on the biodegradation of IBP and diazinon〔0,0-diethyl 0-(2-isopropyl-4-methyl-5-pyrimidinyl) phosphorothioate〕 in silt loam soil with 2.1% organic matter under flooded condition. The persistence of IBP in the soil was shortened by increasing the frequencies of application of the chemical. Enhanced degradation ability in the soil caused by repeated application of IBP was prolonged about 53 days, while the ability did not influence diazinon persistence in the soil. The half-lives of IBP in sterilized soil autoclaved at $121^{\circ}C$ for 30 minutes were about 3 times longer than those in viable soil, suggesting that microbial process was a major factor for IBP degradation in the soil. The total colony number of soil microbes showed little difference between the soils with and without repeated application of IBP. A possible concern of specific soil microorganisms on the pesticide degradation in soil was discussed.

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Estimation Method of Infiltration Capacity for Assessment of Drainage Capacity I (배수성능 평가를 위한 침투능 산정기법에 관한 연구 I)

  • Jeong, Jisu;Shim, Jeonghoon;Hwang, Youngcheol;Lee, Seungho
    • Journal of the Korean GEO-environmental Society
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    • v.20 no.12
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    • pp.49-55
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    • 2019
  • Slope failure analysis entails proper understanding of various factors as well as the characteristics of ground conditions, which are difficult to achieve due to technological limits. Despite a number of past studies to clarify possible factors triggering slope failures, the impact of rainfall characteristics and infiltration rate, which are the key to estimation of slope stability in wet condition, on slope failures still remains unclear. This study has estimated permeability against various unit weights of soil based on constant head permeability tests using Jumunjin standard silica sand. One dimensional infiltration tests were conducted to estimate the infiltration capacity and the amount of infiltration taking into account the permeability and rainfall intensity. The applicability of existing empirical equations for the estimation of infiltration to granular soils was verified on the basis of the test results.

A Comparative Analysis on Channel Forms and Landscapes at Naeseongcheon River and Wicheon River in Gyeongpook Province (경북 내성천과 위천의 하도 형상 및 경관 비교 분석)

  • Lee, Gwang-Ryul
    • Journal of The Geomorphological Association of Korea
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    • v.17 no.4
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    • pp.1-16
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    • 2010
  • Channel topography, sediment properties, channel landscapes and characteristics of land covers in Naeseongcheon and Wicheon River consisting of granites and sedimentary rocks, respectively, are compared and analyzed. Due to the differences of bedrocks, soils and characteristics of land covers in the basins, Wicheon River with the slow flow speed shows the larger variations in river stage than Naeseongcheon River. While Naeseongcheon River fed by the granite sediments throughout granular disintegration hs tthe regular grain size properties with coarse sand in the most of river, Wicheon River fed by sedimentary rocks indicates the dramatic decertses of grain size lower-ward. Naeseongcheon River with channel interferences such as sand-sized sediment transughoations, dredges, and aggregate collections is analyzed as poorer vegetation covers than Wicheon River due to the dramatic changes in channel surfaces.

Assessment of Physiological Activity of Entomopathogenic Fungi with Insecticidal Activity Against Locusts (풀무치에 대하여 살충활성을 보유한 곤충병원성 진균의 생리활성 평가)

  • Lee, Mi Rong;Kim, Jong Cheol;Lee, Se Jin;Kim, Sihyeon;Lee, Seok Ju;Park, So Eun;Lee, Wang Hyu;Kim, Jae Su
    • Korean journal of applied entomology
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    • v.56 no.3
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    • pp.301-308
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    • 2017
  • Locusts, Locusta migratoria (Orthoptera: Acrididae) are periodical unpredictable agricultural pests worldwide and cause serious damage to crop production; however, little consideration has been given to the management of this pest. Herein, we constructed a locust-pathogenic fungal library and confirmed that some fungi could be used as resources for locust management. First, the entomopathogenic fungi were collected from sampled soils using a Tenebrio molitor-based baiting system. For the locust assay, a locust colony was obtained from the National Institute of Agricultural Science and Technology. A total of 34 entomopathogenic fungal granules, which were produced by solid cultures, were placed in the plastic insect-rearing boxes (2 g/box) and nymphs of locust were contained in the box. In 3-7 days, mycosis was observed on the membranous cuticles of the head, abdomen, and legs of locusts. In particular, Metarhizium anisopliae, M. lepidiotae, and Clonostachys rogersoniana exhibited high virulence against the locust. Given that the 34 isolates could be used in field applications, their conidial production and stability (thermotolerance) were further characterized. In the thermotolerance assay, Paecilomyces and Purpureocillium isolates had higher thermotolerance than the other isolates. Most of the fungal isolates produced ca. >$1{\times}10^8conidia/g$ on millet grain medium. In a greenhouse trial, the granular application of M. anisopliae isolate on the soil surface resulted in 85.7% control efficacy. This work suggests that entomopathogenic fungi in a granular form can be effectively used to control the migratory locust.

Feasibility Study of the Stabilization for the Arsenic Contaminated Farmland Soil by Using Amendments at Samkwang Abandoned Mine (삼광광산 주변 비소 오염 토양에 대한 안정화 공법 적용성 평가)

  • Lee, Jung-Rak;Kim, Jae-Jung;Cho, Jin-Dong;Hwang, Jin-Yeon;Lee, Min-Hee
    • Economic and Environmental Geology
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    • v.44 no.3
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    • pp.217-228
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    • 2011
  • The feasibility study for the stabilization process using 5 amendments was performed to quantify As-immobilization efficiency in farmland soils around Samkwang abandoned mine, Korea. For the batch experiments, with 2% and 3% of granular lime(2-5 mm in diameter), leaching concentration of As from the soil decreased by 86% and 95% respectively, compared to that without the amendment. When 5% and 10% of granular limestone was added in the soil, As concentration decreased by 82% and 95%, showing that lime and limestone has a great capability to immobilize As in the soil. From the results of batch experiments, continuous column(15 cm in dimeter and 100 cm in length) tests using granular lime and limestone as amendments was performed. Without the amendment, As concentration from the effluent of the column ranged from 167 ${\mu}g$/L to 845 ${\mu}g$/L, which were higher than Korea Drinking Water Limit(50 ${\mu}g$/L). However, only with 1% and 2% of lime, As concentration from the column dramatically decreased by 97% for 9 years rainfall and maintained below 50 ${\mu}g$/L. With 5% of limestone and the mixed amendment(1% of lime + 2% of limestone), more than 95% diminution of As leaching from the column occurred within I year rainfall and maintained below 20 ${\mu}g$/L, suggesting that the capability of limestone to immobilize As in the farmland soil was outstanding and similar to that of lime. Results of experiments suggested that As stabilization process using limestone could be more available to immobilize As from the soil than using lime because of low pH increase and thus less harmful side effect.

A Study on Selective Adsorption of Phenanthrene Dissolved in Triton X-100 Solution using Activated Carbons (활성탄을 이용한 Triton X-100 용액에서의 phenanthrene의 선택적 흡착에 관한 연구)

  • Ahn, Chi-Kyu;Kim, Young-Mi;Woo, Seung-Han;Park, Jong-Moon
    • Journal of Soil and Groundwater Environment
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    • v.11 no.2
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    • pp.13-21
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    • 2006
  • Polycyclic aromatic hydrocarbons (PAHs) are widespread soil contaminants and major environmental concerns. PAHs have extremely low water solubility and are strongly sorbed to soil. A potential technology for remediation of PAHcontaminated soils is a soil washing with surfactant solutions. While the use of surfactants significantly enhances the performance of soil remediation, operation costs are increased. Selective adsorption of PAHs by activated carbons is proposed to reuse the surfactants in the soil-washing process. The adsorption isotherms of pure chemicals (Triton X-100 and phenanthrene) onto three granular activated carbons were obtained. The selective adsorption of phenanthrene in mixed solution was examined at various concentrations of phenanthrene and Triton X-100. The selectivity results were discussed with pore size distribution of activated carbons and molecular sizes of phenanthrene and the Triton X-100 monomer. The selectivity for phenanthrene was much larger than 1 regardless of the particle size of activated carbons. The selective adsorption using activated carbons with proper pore size distribution would greatly reduce the material cost for the soil washing process by the reuse of the surfactants.

Evaluation of Shear Zone in Direct Shear Test Using Elastic, Electromagnetic Waves and Cone Tip Resistance (전단파, 전자기파 및 콘 관입저항력을 이용한 직접전단실험시 전단영역 특성 평가)

  • Byun, Yong-Hoon;Truong, Q. Hung;Tran, M. Khoa;Lee, Jong-Sub
    • Journal of the Korean Geotechnical Society
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    • v.27 no.2
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    • pp.43-52
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    • 2011
  • The characteristics of shear zone in granular soils largely affect the stability of geo-structures. The goal of this study is to evaluate shear zone in a direct shear test using shear wave, electrical resistivity, and cone tip resistance. Bender elements and electrical resistivity probe are embedded into the wall of a direct shear box made of transparent acrylic material to estimate the shear wave velocities and the electrical resistivity at shear and non-shear zones. At the point of peak and residual strength, micro cone penetration test which can be available to measure tip resistance has been performed. Experimental results show that the shear wave velocities at upper shear zone increase during shearing while the values remain constant at bottom and lower shear zone. Also, resistivities at lower shear zone depend on relative density while resistivities at bottom remain constant. The results of cone penetration test demonstrate the correlation of the cone tip resistance and small strain shear modulus at shear zone. This study suggests that the application of the modified direct shear box including shear wave, electrical resistivity and the micro cone tip resistance may become effective tools for analyzing the characteristics of a shear zone.

Study on Removal of Cesium in Water Treatment System (물속의 방사성핵종(세슘) 제거율 연구)

  • Jeong, Gwanjo;Son, Boyoung;Ahn, Chihwa;Lee, Suwon;Ahn, Jaechan;Kim, Bogsoon;Chung, Deukmo
    • Journal of Korean Society of Environmental Engineers
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    • v.38 no.1
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    • pp.8-13
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    • 2016
  • This study investigated the removal of a radioactive cesium ($Cs^+$) in the water at the water treatment processes. Since cesium is mostly present as the $Cs^+$ ion state in water, it is not removed by sand filtration, and coagulation with polyaluminum chloride (PACl), powdered activated carbon (PAC) and mixture of PACl and PAC. However, it is known that the removal rate of cesium increases as the turbidity increases in raw water. As the turbidity was adjusted by 74 NTU and 103 NTU using the surrounding solids near G-water intake and yellow soils, removal rate of cesium was about 56% and 51%, respectively. In case of a GAC filtration with supernatants after jar-mixing/setting was conducted, 80% of cesium is approximately eliminated. The experimental results show that it is efficient to get rid of cesium when the turbidity of the raw water is more than 80 NTU. In case of a GAC filtration, about 60% of cesium is removed and it is considered by the effect of adsorption. Cesium is not eliminated by microfiltration membrane while about 75% of cesium is removed by reverse osmosis.

Evaluation on Stress-Strain-Strength Behavior of the Textile Encased Soils via Triaxial Compression Tests (삼축압축시험을 통한 섬유로 구속된 흙의 응력-변형률-강도 거동 평가)

  • Yoo, Wan-Kyu;Kim, Byoung-Il;Cho, Wanjei
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.33 no.2
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    • pp.643-653
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    • 2013
  • Recently, there are an increasing number of studies on the method of wrapping the outer wall of granular piles with geosynthetic fibers such as geotextile or geogrid that has a certain level of tensile strength as an alternative method for the ground improvement techniques. In this study, triaxial compression tests are performed on the sand and clay specimen encased with various textiles to evaluate the reinforcing effect with regard to the tensile strength of the textile. Furthermore, triaxial compression tests are performed on the clay specimen inserted by sand only and sand encased with geosynthetics to compare behavioral differences between the conventional sand compaction pile and geosynthetic encased sand pile with regard to the replacement ratio, ${\alpha}_s$ and the tensile strength of the geosynthetics. Based on the experimental results, the strength enhancement due to the textile is affected by the longitudinal tensile strength rather than the transverse one of the applied textile. The effect of the confinement by the textile encasement results in the large increase of the cohesions. The overall behaviors, such as shear strength, pore pressure parameter at failure and stress ratio, of the geosynthetic encased sand pile is quite different from those of the conventional sand compaction pile.