• 한국분말재료학회지
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• 제13권4호
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• pp.263-268
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• 2006

In this study, the colloidal stability and sedimentation behavior of crystalline $TiO_2$ particles (300nm) in various organic solvents have been investigated by means of a backscattered light flux profile (Turbiscan). The backscattered light flux profiles revealed that the $TiO_2$ nanoparticles were readily sedimented in water, methyl alcohol, and ethyl alcohol due to a flocculation-induced particle growth, while a particle coalescence and a sedimentation of the $TiO_2$ nanoparticles were hardly observed in isopropyl alcohol. The migration velocities of the $TiO_2$ particle were measured as around 6.15/min, 12.53 m/min, 6.51m/min, and 0.18m/min for water, methyl alcohol, ethyl alcohol, and isopropyl alcohol, respectively, showing a remarkably slow migration of the $TiO_2$ particles in isopropyl alcohol.

• 상하수도학회지
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• 제21권2호
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• pp.187-193
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• 2007

Reynolds and Froude numbers, along with tracer tests, have been widely used to estimate hydrodynamics in full-scale horizontal sedimentation basin in water treatment plants (WTPs). In spite of this, the former numbers do not reflect actual operating conditions, instead most often being based on the dimensions of the structures. The index and graphic analyses most often used were found to be too subjective to accurately analyze tracer test results. In order to overcome these limitations, dispersion number was applied for analysis of tracer test results. Tracer tests were conducted in eight full-scale sedimentation basins in six WTPs, and then analyzed by index and graphic analyses as well as by dispersion number. The dispersion number was more useful as an indicator of the hydrodynamic behavior in the basin. It was also found that as dispersion number decreased, flow approached the ideal for plug flow in which case, higher sedimentation efficiency could be expected.

• 상하수도학회지
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• 제27권4호
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• pp.469-477
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• 2013

In order to investigate the influence of feed water inequity on the settling performance for parallel arranged upflow sedimentation basin in domestic G_WTP(Water Treatment Plant), CFD(Computational Fluid Dynamics) simulation were employed and ADV(Acoustic Doppler Velocimeter) measurements were carried out. From the results of both CFD simulations and ADV measurements, the differences among inlet flow rates to each inlet structure make turbulent energy dissipation uneven overall sedimentation basin. Especially local velocities in the near of both side wall were observed over the design overflow rate(74.4 mm/min). Also, it was confirmed that this inequity of inlet flow would exert an serious influence on the turbidity of settled water which is out from 8 troughs. Even though experimental velocities in full scale basin about 20% higher than the simulated, the results of ADV measurement were in good accordance with those of CFD simulations.

• 한국지반공학회논문집
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• 제19권5호
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• pp.89-98
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• 2003

퇴적속도의 변화를 고려한 자중압밀해석과 토질조사시험결과의 비교분석을 통하여 22년 동안 방조제 앞에 두께 5∼12m가 급속히 퇴적된 간석지는 미압밀상태에 있음을 확인하였다. 또한 압밀계수$c_v$=0.0005∼0.001$cm^2$/S인 퇴적층은 평균퇴적속도 $v_s$$\phi$=1∼5cm/yr 이상이면 미압밀상태의 가능성이 높으며, 퇴적속도가 초기에 빠르고 후기에 느린 경우 보다 초기에 느리고 후기에 빠른 경우가 훨씬 큰 잔류 과잉간극수압이 존재한다는 것을 알 수 있었다. 그리고 미압밀상태의 간석지는 압밀침하량이 훨씬 크므로, 최근에 급속히 퇴적된 간석지를 매립하는 경우 미압밀 여부의 평가와 미압밀을 고려한 압밀해석이 필요하다는 결론을 얻었다.

• Geomechanics and Engineering
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• 제33권2호
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• pp.121-131
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• 2023

Clay sedimentation has been widely analyzed for its application in a variety of geotechnical constructions such as mine tailing, artificial islands, dredging, and reclamation. Chemical flocculants such as aluminum sulfate (Al₂(SO₄)₃), ferric chloride (FeCl₃), and ferric sulfate (Fe(SO₄)₃), have been adopted to accelerate the settling behaviors of clays. As an alternative clay flocculant with natural origin, this study investigated the settling of xanthan gum-treated kaolinite suspension in deionized water. The sedimentation of kaolinite in solutions of xanthan gum biopolymer (0%, 0.1%, 0.5%, 1.0%, and 2.0% in a clay mass) was measured until the sediment height was stabilized. Kaolinite was aggregated by xanthan gum via a direct electrical interaction between the negatively charged xanthan gum molecules and positively charged edge surface and via hydrogen bonding with kaolinite particles. The results revealed that the xanthan gum initially bound kaolinite aggregates, thereby forming larger floc sizes. Owing to their greater floc size, the aggregated kaolinite flocs induced by xanthan gum settled faster than the untreated kaolinite. Additionally, X-ray computed tomography images collected at various depths from the bottom demonstrated that the xanthan gum-induced aggregation resulted in denser sediment deposition. The findings of this study could inspire further efforts to accelerate the settling of kaolinite clays by adding xanthan gum.

• 한국세라믹학회지
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• 제43권10호
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• pp.635-639
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• 2006

Dispersion behavior of the slurries consisted of Pb or Bi-based glass frits, which are used for the fabrication of green sheet as PDP front panel transparent dielectric, was examined in non-aqueous solvent system. Measurements of sedimentation height and viscosity were conducted to determine proper dispersion condition in the various solvent and dispersant system. Azotropic compound and ethyl acetate were used as the solvent and ammonium-type dispersant was applied to the slurries. All slurries were dispersed well in azotropic solvent system involving 20$\sim$50 vol% ethyl acetate at 2$\sim$3 wt% dispersant content. Especially, dispersion behavior was notably improved in the addition of ethyl acetate in the Bi-based frit slurry.

• 한국세라믹학회지
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• 제42권11호
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• pp.737-742
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• 2005

Rheological properties of ordinary portland cement (OPC) containing metakaoline (MK), granulated blast furnace slag (GBS) and polycarboxylate type superplasticizer (PCA) were investigated using a mini-slump test, sedimentation test and viscometer. Fluidity of cement pastes containing MK (OPC-MK, OPC-MK-GBS systems) with PCA were higher than those of the cement pastes without MK(OPC, OPC-GBS systems). Colloid suspensions with $0.1\%$ PCA were changed from stable sedimentation behaviors to flocculation behaviors in the OPC-MK, OPC-GBS and OPC-MK-GBS systems. The colloid suspensions showed stable sedimentation behaviors with PCA greater than $0.2\%$. The OPC system showed shear thinning behavior. However, the other systems showed weak shear thinning behaviors with PCA. Rheological properties of cement pastes were improved when MK and GBS were contained together. The rheological properties of OPC-MK, OPC-GBS and OPC-MK-GBS systems were improved by PCA added greater than $0.2\%$.

• 상하수도학회지
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• 제21권1호
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• pp.131-138
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• 2007

A rainwater utilization facility consists of its catchment area, treatment facility, storage tank, supply facility and pipes in general. The rainwater storage tank which occupies the largest area of the facility has been usually considered quantitatively for determining the storage capacity. Hence, there is little information on water quality improvement by sedimentation in a rainwater storage tank in operation. In this study, we measured the rainwater quality in a rainwater storage tank in operation during late spring and summer, and showed water quality improvement of turbidity removal of 25~46% by sedimentation in a rainwater storage tank under a fixed water level without inflow and outflow after runoff ceased. It is necessary to have a considerable distance between the inlet and outlet of the tank and, if possible, it is recommended that the design should allow for an effective water depth of over 3 m and supply rainwater near the water surface. The operation method which increases the retention time by stopping rainwater supply for insuring low turbidity is recommended when the turbidity of rainwater runoff is high. And also more efficient operation and maintenance of the rainwater utilization facility is expected through the tailored design and operation of the facility considering particle removal and behavior.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2008년도 추계 학술발표회
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• pp.407-426
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• 2008

The bentonite slurry has been used as the stabilize suspension for wet process bored pile construction in Thailand. The bentonite suspension has benefit on filtration in the sand layer, but it creates thick cake film along pile shaft and loose sedimentation at pile toe. The base grouting technique was widely used to rectify the soft base or loose sedimentation problem of bored pile. The base grouting technique was not increased only end bearing capacity, but was also more increase in skin friction capacity of the bored piles. The comprehensive researches on base grouting was carried out by installing PVC casing inside the shaft to allow the drilling through the pile base in order to collect the soil sample below the pile tip. The polymer based slurry recently was used to replace the bentonite slurry to overcome the thick cake film along pile shaft as well as loose sedimentation at pile toe. The extent research on polymer slurry by physical model was performed to verify the real behavior of polymer. The appropriate mixing ratio of polymer was proposed. The design skin friction coefficient, $\beta$ and end bearing coefficient, Nq, for sand layer base on fully instrumented tested pile were proposed. The application on remedial of the lose capacity bored pile with large displacement in Bangladesh was proposed and discussed.

• 한국수자원학회:학술대회논문집
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• 한국수자원학회 2005년도 학술발표회(1)
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• pp.416-417
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• 2005