• Title, Summary, Keyword: Settling behaviour

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Settling and Consolidation Behaviour of Cohesive Soil Slurry (점토슬러리의 침강 및 압밀 거동에 관한 연구)

  • Lee, MyungHo;Kim, Dae-Ho;Kim, Soo Sam
    • Journal of The Korean Society of Civil Engineers
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    • v.28 no.3C
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    • pp.143-148
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    • 2008
  • This paper demonstrates settling and further consolidation behaviour of dredged clayey soils during landfilling. The effects of initial moisture content, electrolyte type and concentration on settling and consolidation behaviour were examined and evaluated by laboratory column tests. Electrokinetic tests were carried out with modified settling column to compare the soil behaviour under the gravity. From the testing results, the settling velocity increased due to the effects of cations in the electrolyte solution, and electrically induced settlements were found to be greater than those under the gravity.

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Settling behaviour of clay slurries enhanced by using electrokinetics (동전기에 의한 점토슬러리의 침강 촉진에 관한 연구)

  • Kim, Dae-Ho;Kim, Soo-Sam;Lee, Myung-Ho
    • Proceedings of the Korean Geotechical Society Conference
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    • pp.1061-1064
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    • 2008
  • A completion of settling process takes a lot of time for dredged materials of high moisture content, such as contaminated sludge, in landfill site. In general, additives (e.g. flocculants) are used for reducing settling time of such colloidal material, which results in the increase of sludge volume, and hence much space is required in landfill site. This study is to suggest alternative method in order to enhance the settling process of cohesive clayey soils. A number of gravitational sedimentation tests as well as electrokinetic experiments were conducted to investigate the variation of initial moisture content on the settling behaviour of clay slurry. Surface settlement, electric current and local voltage gradient were monitored during the experiment, and moisture content and soil pH were measured after the experiment. From the results, the application of electrokinetics was found to be effective in volume reduction (i.e. increase of settling velocity and decrease of final moisture content) by comparison with gravitational settling process.

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Experiment on Settling Behaviour of Fine Mineral Particles (광물성 미립자의 침전거동에 관한 실험)

  • Kim, Jong-Woo
    • Journal of Korean Society of Hazard Mitigation
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    • v.5 no.1
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    • pp.13-21
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    • 2005
  • Experiments on settling behaviour of fine-grained particles without destroying the large fragile aggregates were carried out in still water with a CCD (Charged Coupled Device)-Camera. The experiments dealt with the measuring of the vertical concentration profile of cohesive particles with a CCD-Camera and the physico-chemical influences (NaCl, density, temperature and pH value) on the vertical distribution of the concentration. The vertical concentration profile of fine suspended particles (alumina and quartz) was possible up to $20,000\;mg/{\ell}$ with a CCD-Camera. The vertical concentration profile of cohesive sediments was on the decrease because of the increasing initial concentration, temperature and salinity. The vertical concentration profile of alumina was on the decrease quicker than quartz with increasing salinity. Furthermore, the pH value affects the settling behaviour of alumina. At a PH value of 4.2 the settling rate of the particles was very low and on the increase until pH 8.9 because of the aggregation behaviour of particles. From the PH value of 9 the average settling velocity was on the decrease.

Settling Mode of the Dredged Soil (준설토의 침강형태에 관한 연구)

  • 윤상묵;장병욱;차경섭
    • Magazine of the Korean Society of Agricultural Engineers
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    • v.45 no.1
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    • pp.63-73
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    • 2003
  • The settling of the dredged soil may vary with mineral composition, grain size distribution, initial water content and salt concentration of suspension of the site. A series of settling column test was performed to investigate the behaviour of solid suspension material from dredging and reclamation. Settling mode was divided into four types from the observation of interface and settling curves of clay minerals and marine clay samples, and the relationship charts of salt concentration and the initial water content were established to use in the dredging operation with any salt concentration. The critical initial water content which was defined as a threshold of zone settling and the consolidation settling was varied with salt concentration of water and was proportional to the plasticity of soil in sea water.

A Study on the Electrokinetic Acceleration of Clayey Particles Settling in Suspension (동전기에 의한 점토슬러리의 침강 촉진에 관한 연구)

  • Kim, Dae-Ho;Lee, MyungHo;Kim, Soo Sam
    • Journal of The Korean Society of Civil Engineers
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    • v.30 no.1C
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    • pp.1-5
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    • 2010
  • The river maintenance processing has revealed that the river beds in Korea have been significantly polluted in various ways for the last two decades. Thus, the dredging, transportation and landfilling of these contaminated materials are attracting public attention these days. In this study, electrokinetic method was applied in order to accelerate the settling processes of clay particles in suspension and evaluate the factors affecting the settling behaviour. It has been found from the testing results that the settling velocity under the influence of electrokinetics was much faster than the gravitational one, and the water content of slurry soil reduced significantly after the electrokinetic processing. The initial water content of slurry soil should be one of the important factors affecting the settling behaviour as well as variation of water content, and hence the electrokinetic processing would be the cost-effective method for the field application.

Experiment on Settling Velocity of Suspended Mineral Particles (부유된 광물성 입자의 침강 속도에 관한 실험)

  • Kim, Jong-Woo
    • Journal of Korea Water Resources Association
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    • v.40 no.9
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    • pp.723-734
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    • 2007
  • This study was to investigate the settling velocity which is an important factor for the prediction of cohesive deposition under the various densities of particle and dissolved ion addition$(Na^+,\;Cl^-,\;OH^-,\;H^+)$ in rivers, ports, reservoirs and lakes. Settling velocity of suspended fine particles in still water was measured with a pressure sensor (maximum 10 mbar). At the initial concentration of 20g/l of alumina and quartz the average settling velocities were high due to the aggregation behaviour of particles. At this point it was 0.185 mm/s (alumina) and 0.022 mm/s (quartz). Above this initial concentration it was on the decrease owing to the hindered settling. The higher the salinity is, the faster the settling velocity of alumina and quartz is. Furthermore, in an acid condition the average settling velocity of alumina was on the decrease. In an alkaline water, which causes strong flocculation, the average settling velocity of alumina it was observed on the increase. However, in an alkaline medium the low average settling velocity of quartz powder was measured.

Effects of Organic Loading Rates on Treatment Performance in a Polyvinylidene Media Based Fixed-Film Bioreactor

  • Ahmed, Zubair;Oh, Sang-Eun;Kim, In S.
    • Environmental Engineering Research
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    • v.14 no.4
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    • pp.238-242
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    • 2009
  • This study investigated the effects of organic loading rates on simultaneous carbon and nitrogen removal in an innovative fixed-film aerobic bioreactor. The fixed-film bioreactor (FFB) was composed of a two-compartment aeration tank, in which a synthetic filamentous carrier was submerged as biofilm support media, and a settling tank which polyvinylidene media (Saran) was used as settling aid for suspended solids. Three different organic loading rates, ranging from 0.92-2.02 kg chemical oxygen demand/$m^3$/day were applied by varying hydraulic retention time (HRT). The total soluble organic carbon removal efficiencies were in the range of 90-97%. The removal efficiency of ammonia was found to be in the range of 70-84%. Total nitrogen removal efficiency was found to be in the range of 40-45%, which indicates that denitrification reactions occurred simultaneously in the attached biofilm on the fibrous media in the aeration tank. The settling performance of suspended solids was significantly improved due to the presence of Saran media in the settling compartment, even for a short HRT. The fixed-film aerobic bioreactor used in this study demonstrated efficient treatment efficiency even at higher organic loading rates and at short HRTs.

Dynamics of Estuarine Circulation in Semi-closed Inner Bay (폐쇄성 내만에서의 Estuary순환의 중요성)

  • 김종인;류청로
    • Journal of Ocean Engineering and Technology
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    • v.15 no.4
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    • pp.34-45
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    • 2001
  • In the persent study, we conducted numerical experiments using a three-dimensional baroclinic equation model and a Lagrangian method for clarifying the hydrodynamics in Osaka Bay under the yearly mean discharge and visualizing the behaviour of particles of different settling velocity discharged from Yodo River and sedimentation pattern on the sea bottom. Particles are transported from the Yodo River to the south direction by the residual circulation of the bay head at the first stage, and after most of suspended solids particles are settled down at any layer and returned in the south-east coastal area through bottom layers by an estuarine circulation. The results show that estuarine circulation plays an important part of suspended solids transportation in the Osaka Bay.

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Analysis of Characteristics of Cohesive Sediment Settling (점착성 퇴적물의 침전 특성 분석)

  • Kim, Jong-Woo;Yoon, Sei-Eui;Lee, Jong-Tae
    • Journal of Korea Water Resources Association
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    • v.38 no.2
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    • pp.133-142
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    • 2005
  • The settling concentration of fine suspended solid particles(alumina(Al$_2$O$_3$) and quartz(SiO$_2$)) is investigated with the physico-chemical effects(initial concentration, pH and NaCl). Laboratory tests have confirmed the significant influence of increasing initial concentration and salinity which can lead to flocculation due to the intermolecular attraction. Furthermore, the influence of the pH value on the concentration-time corves of alumina has been on firmed. Besides a numerical model to predict the behaviour of cohesive deposit under still water is analyzed by solving the unsteady one-dimensional diffusion-advection equation with a explicit, implicit, Crank-Nicolson and finite difference scheme. The model predicts the existence of an equilibrium concentration. Application of the model with implicit centered difference to data from settling experiments shows a similar distribution.