• Title/Summary/Keyword: Soil Improvement

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Effect of Fly Ash on Productivity of Tomato and Improvement of Soil (토마토 생산성과 토양개량에 미치는 석탄회 시용의 영향)

  • Lee, Cheol-Hee
    • Korean Journal of Plant Resources
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    • v.20 no.1
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    • pp.93-98
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    • 2007
  • In the present experiment, fly ash application to soil generally improved soil pH condition. The improvement of soil pH was greater with bituminous fly ash than with anthracite fly ash. Treatment of fly ash also made available phosphate content increased. But phosphate content in cultivated tomato plants was in inverse proportion to content in soil due to high pH of experimental soil as well as hot and dry weather. Amount of phosphate in plants had a strong positive effect on the yield of tomato. Number and weight of harvested fruits was greatest from July 21 to July 30, the time considered as peak harvesting period of second fruit truss. In conclusion, the application of fly ash improved physico-chemical properties of experimental soil.

Improvement of Soil Moisture Initialization for a Global Seasonal Forecast System (전지구 계절 예측 시스템의 토양수분 초기화 방법 개선)

  • Seo, Eunkyo;Lee, Myong-In;Jeong, Jee-Hoon;Kang, Hyun-Suk;Won, Duk-Jin
    • Atmosphere
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    • v.26 no.1
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    • pp.35-45
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    • 2016
  • Initialization of the global seasonal forecast system is as much important as the quality of the embedded climate model for the climate prediction in sub-seasonal time scale. Recent studies have emphasized the important role of soil moisture initialization, suggesting a significant increase in the prediction skill particularly in the mid-latitude land area where the influence of sea surface temperature in the tropics is less crucial and the potential predictability is supplemented by land-atmosphere interaction. This study developed a new soil moisture initialization method applicable to the KMA operational seasonal forecasting system. The method includes first the long-term integration of the offline land surface model driven by observed atmospheric forcing and precipitation. This soil moisture reanalysis is given for the initial state in the ensemble seasonal forecasts through a simple anomaly initialization technique to avoid the simulation drift caused by the systematic model bias. To evaluate the impact of the soil moisture initialization, two sets of long-term, 10-member ensemble experiment runs have been conducted for 1996~2009. As a result, the soil moisture initialization improves the prediction skill of surface air temperature significantly at the zero to one month forecast lead (up to ~60 days forecast lead), although the skill increase in precipitation is less significant. This study suggests that improvements of the prediction in the sub-seasonal timescale require the improvement in the quality of initial data as well as the adequate treatment of the model systematic bias.

Soil Stabilization with time and Rice Husk Ash (Rice husk ash를 이용한 토질안정처리)

  • 민덕기;황광모;김현도;황택진
    • 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.

Strength of Improved Soil on the Work-conditions of Deep Mixing Method (시공조건에 따른 심층혼합처리 개량체의 강도에 관한 연구)

  • Lee, Kwang-Yeol;Yoon, Sung-Tai;Kim, Sung-Moo;Han, Woo-Sun
    • Journal of the Korean Geotechnical Society
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    • v.23 no.7
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    • pp.99-104
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    • 2007
  • The deep soil mixing, on ground modification technique, has been used for many diverse applications including building and bridge foundations, port and harbor foundations, retaining structures, liquefaction mitigation, temporary support of excavation and water control. This method has the basic objective of finding the most efficient and economical method for mixing cement with soil to secure settlements through improvement of stability on soft ground. In this research, the experiments were conducted on a laboratory scale with the various test conditions of mixing method; the angle of mixing wing, mixing speed. Strength and shapes of improved soil of these test conditions of deep mixing method were analysed. From the study, it was found that the mixing conditions affect remarkably to the strength and shapes of improved soils.

Application of magnesium to improve uniform distribution of precipitated minerals in 1-m column specimens

  • Putra, Heriansyah;Yasuhara, Hideaki;Kinoshita, Naoki;Hirata, Akira
    • Geomechanics and Engineering
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    • v.12 no.5
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    • pp.803-813
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    • 2017
  • This study discussed the possible optimization of enzyme-mediated calcite precipitation (EMCP) as a soil-improvement technique. Magnesium chloride was added to the injection solution to delay the reaction rate and to improve the homogenous distribution of precipitated minerals within soil sample. Soil specimens were prepared in 1-m PVC cylinders and treated with the obtained solutions composed of urease, urea, calcium, and magnesium chloride, and the mineral distribution within the sand specimens was examined. The effects of the precipitated minerals on the mechanical and hydraulic properties were evaluated by unconfined compressive strength (UCS) and permeability tests, respectively. The addition of magnesium was found to be effective in delaying the reaction rate by more than one hour. The uniform distribution of the precipitated minerals within a 1-m sand column was obtained when 0.1 mol/L and 0.4 mol/L of magnesium and calcium, respectively, were injected. The strength increased gradually as the mineral content was further increased. The permeability test results showed that the hydraulic conductivity was approximately constant in the presence of a 6% mineral mass. Thus, it was revealed that it is possible to control the strength of treated sand by adjusting the amount of precipitated minerals.

A Numerical Analysis on Pneumatic Fracturing for in-situ Remediation (비포화대 오염정화 설계를 위한 공압파쇄 모사 해석)

  • Kwon, Mi-Seon;Park, Eun-Gyu;Lee, Cheol-Hyo;Kim, Yong-Seong;Kim, Nam-Jin
    • Journal of Soil and Groundwater Environment
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    • v.15 no.6
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    • pp.53-63
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    • 2010
  • Pneumatic fracturing is an emerging tool to enhance the remediation efficiency of contaminated unsaturated zones by injecting high pressure air and inducing artificial fracture networks. Pneumatic fracturing is reported to be well suited for the cases where the contaminated unsaturated zone thickness is less than 5 m as many contaminated domestic sites in Korea. Nevertheless, there have been almost no studies carried out on the site-specific efficiency and the optimized design of pneumatic fracturing considering the unsaturated zone characteristics of Korea. In this study, we employ numerical simulations to compare the efficiency of pneumatic fracturing on the aspect of the site remediation and the porosity improvement at several hypothetic unsaturated zones composed of four typical soil types. According to the simulation results, it is found that the zone with fine grains soil such as clay and silt shows better efficiency than the zone composed of coarse grains in terms of air flow and porosity enhancements. The results imply that pneumatic fracturing may improve the efficiency of site reclamation by jointly or independently applied to the many contaminated sites in Korea.

DESIGN CONSIDERATIONS AND MONITORING RESULTS OF AN UNDERWATER EARTH DAM

  • Van Impe, W.F.
    • Proceedings of the Korean Geotechical Society Conference
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    • 2009.03a
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    • pp.1210-1224
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    • 2009
  • The present paper illustrates the outcome of the monitoring of the consolidation behavior of a soft foundation soil under a large submerged sand embankment. Measurements of settlements and excess pore water pressures showed a good agreement with predictions evaluated using the large strain consolidation theory. Soft soil improvement by means of deep mixing has been optimized. Moreover, the principles and developments of underwater geosynthetics applications are discussed.

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Mechanical Characteristics of Reinforced Soil(II) -Fiber Reinforced Soil- (보강 혼합토의 역학적 특성(II) -섬유 혼합토-)

  • Song, Chang Seob;Lim, Seong Yoon
    • Journal of the Korean Society of Environmental Restoration Technology
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    • v.5 no.6
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    • pp.37-42
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    • 2002
  • This study has been performed to investigate the physical and mechanical characteristics of compaction, volume change and compressive strength for reinforced soil mixed with polypropylene fiber, and to confirm the reinforcing effects with admixture such as polypropylene fiber. To this end, a series of compaction test and compression test was conducted for clayey soil(CL) and polypropylene fiber reinforced soil. In order to determine proper moisture contents and mixing ratio, pilot test was carried out for natural soil and PFRS(polypropylene fiber reinforced soil). And the mixing ratio of mono-filament fiber and fibrillated polypropylene fiber admixture was 0.1%, 0.3%, 0.5% and 1.0% by the weight of dry soil. From the experimental results, it was found that the optimum moisture contents(OMC) increased with the mixing ratio of fiber, but the maximum dry unit weight and the volume change was decreased with the mixing ratio. It means that the improvement of the workability and the reduction of the weight of embankment was done by the addition of the polypropylene fiber. And, from the compression test results, it was found that the addition of the polypropylene fiber remarkably improved the compressive strength of PFRS. And it was observed in the viewpoint of strength that the fibrillated polypropylene fiber reinforced soil was more effective than the mono-filament polypropylene fiber reinforced soil.

The controversial points and a remedy on evaluation of heavy metal contamination in standard method for examination of soil in Korea. (국내 토양오염 공정시험방법중 중금속 관련 오염평가의 문제점과 개선책)

  • 오창환;유연희;이평구;박성원;이영엽
    • Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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    • 2000.11a
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    • pp.298-301
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    • 2000
  • Heavy metals are extracted from stream sediments, roadside soils and sediments and soils and tailings from mining area using partial extraction, acid digestion and HF-digestion. Compared to amounts of heavy metals extracted using partial extraction, those extracted using acid digestion are higher by 2.0∼220.9 times in Cu, 2.4∼2806.1 times in Pb, 1.3∼121 times in Cd, 14.1∼1300885 times in Fe, 1.2∼271.5 times in Mn, 1.3∼372.5 times in Zn, 2.2∼1734.5 times in Cr. Although partial extraction, which extracts less amounts of heavy metals from soil compared to acid digestion, is used in domestic standard method for examination of soil, domestic soil standard for heavy metals in non-agricultural and industrial areas is higher than soil standard in foreign countries which use acid digestion, For improvement of the domestic standard method for assessment of soil, it is suggested to lower the domestic soil standard for heavy metals or to change pretreatment method for extracting heavy metals from partial extraction to acid digestion with modifying the soil standard.

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Effect of slag on stabilization of sewage sludge and organic soil

  • Kaya, Zulkuf
    • Geomechanics and Engineering
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    • v.10 no.5
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    • pp.689-707
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    • 2016
  • Soil stabilization is one of the useful method of ground improvement for soil with low bearing capacity and high settlement and unrequired swelling potential. Generally, the stabilization is carried out by adding some solid materials. The main objective of this research was to investigate the feasibility of stabilization of organic soils and sewage sludge to obtain low cost alternative embankment material by the addition of two different slags. Slags were used as a replacement for weak soil at ratios of 0%, 25%, 50%, 75% and 100%, where sewage sludge and organic soil were blended with slags separately. The maximum dry unit weights and the optimum water contents for all soil mixtures were determined. In order to investigate the influence of the slags on the strength of sewage sludge and organic soil, and to obtain the optimal mix design; compaction tests, the California bearing ratio (CBR) test, unconfined compressive strength (UCS) test, hydraulic conductivity test (HCT) and pH tests were carried out on slag-soil specimens. Unconfined compressive tests were performed on non-cured samples and those cured at 7 days. The test results obtained from untreated specimens were compared to tests results obtained from soil samples treated with slag. Laboratory tests results indicated that blending slags with organic soil or sewage sludge improved the engineering properties of organic or sewage sludge. Therefore, it is concluded that slag can be potentially used as a stabilizer to improve the properties of organic soils and sewage sludge.