• Proceedings of the Korean Geotechical Society Conference
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• 2010.09a
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• pp.1245-1252
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• 2010

Many industrialized countries are confronted with a difficulty about reuse of closed waste landfill. facilities. Especially, the demand of closed waste landfill maintenance and reuse nearby urban area has been increased, because of the shortage of usable land and extend of urban area. For the safe reuse of closed waste landfill, the most important check point is the effect of waste landfill on environment abound them. However, the non-sanitary closed waste landfill generally have no leachate lining system, therefore, the in-situ lining system such as sheet-pile, and vertical slurry wall etc. was needed to prevent the leachate outgoing from the waste landfill. In this paper present the case history of performance evaluation of vertical slurry wall by tracer tests.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.2B
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• pp.161-170
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• 2006

A tracer test technique using a radioisotope was proposed to investigate pollutant mixing characteristics in rivers. The main advantages of radioisotope as a tracer in field tests are that it can be detected easily, and that its detection range is quite large. Also, using the radioisotope, the amount sorbed by the bed material and the biota may be a minimum. Field tracer tests were conducted at seven different sites in natural rivers with various meandering pattern. Based on the acquired data, the behavior of the tracer cloud in the intermediate-field was examined two-dimensionally, and dispersion coefficients were calculated using several evaluation methods. Results revealed that the tracer cloud was transported skewed to the outer bank and dispersion coefficients in bends were larger than those in straight reaches.

• 한국방재학회:학술대회논문집
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• 2008.02a
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• pp.799-802
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• 2008

General behaviors based on hydraulic characteristics of natural streams and channels have been recently analyzed and developed via various numerical models. However in the states of natural hydraulics, an experimental research must be performed simultaneously with the mathematical analysis due to effects of hydraulic properties such as meander, sediment, and so on. In this study based on 2-D advection-dispersion equation, flow and tracer experiments were performed in the S-curved meandering laboratory channel with a rectangular cross-section. The channel was equipped with instrument carriages which was equipped with an auto-traversing system to be used with velocity measuring sensors throughout the depth and breadth of the flow field. To measure concentration distribution of the salt solution was adjusted to that of the flume water by adding methanol and a red dye (KMnO4) was added to aid the visualization of the tracer cloud, the tracer was instantaneously injected into the flow as a full-depth vertical line source by the instantaneous injector and the initial concentration of the tracer was 100,000 mg/l. The secondary current as well as the primary flow pattern was analyzed to investigate the flow distribution in the meandering channels. The velocity distribution of the primary flow for all cases skewed toward the inner bank at the first bend, and was almost symmetric at the crossovers, and then shifted toward the inner bank again at the next alternating bend. Thus, one can clearly notice that the maximum velocity occurs taking the shortest course along the channel, irrespective of the flow conditions. The result of the tracer tests shows that pollutant clouds are spreading following the maximum velocity lines in each cases with various mixing patterns like superposition, separation, and stagnation of pollutant clouds. Flow characteristics in each cases performed in this study can be compared with tracer dispersion characteristics with using evaluation of longitudinal and transverse dispersion coefficients(LDC, TDC). As expected, LDC and TDC in meandering parts have been evaluated with increasing distribution and straight parts have effected to evaluate minimum of LDC and TDC due to symmetric flow patterns and attenuations of secondary flow.

• KIEAE Journal
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• v.12 no.1
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• pp.29-34
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• 2012

As a series of studies about natural ventilation driven by wind in basement parking lots of apartment, the influence of opening size and surrounding buildings on ventilation rate was analyzed. Natural ventilation in underground parking lots almost rely on wind than temperature difference. To investigate natural ventilation driven by wind, wind tunnel tests by using scale model and tracer gas method were conducted. $CO_2$-gas concentration was measured, natural ventilation rates were calculated. The experimental results showed that the natural ventilation rate is more reliable to wind direction and surrounding building than opening size and distance between buildings. It was verified that surrounding buildings play a principal role in increasing air flow rate by accelerating wind speed, and growing turbulence intensity. And it showed that ventilation performance is able to be increased by oblique wind to entrance ramp than head on wind in underground parking lots with surrounding buildings.

• Journal of Environmental Science International
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• v.20 no.5
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• pp.581-587
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• 2011

Industrial natural ventilation systems consist of gravity ventilator, the high/low windows and doors. Especially, the high windows play an important role in the industrial natural ventilation systems. Generally speaking, industrial high windows are divided into 3 types; louver type, $45^{\circ}$ open type and $90^{\circ}$ open type. This study was numerically and experimentally conducted. Three types of windows were tested to know the ventilation characteristics and estimate the ventilation efficiencies. Numerically, computational fluid dynamics software (AIR PAK Ver. 2.0) was used to observe the flow characteristics inside the industrial building and the concentration contours generated by the tracer gas method. Experimentally, the flow visualization technique and the tracer gas method were applied with the model building to characterize the flow pattern inside the model building and to estimate the ventilation efficiencies with the different windows. It was found that $90^{\circ}$ open type window was most effective for the discharge of pollutants from the industrial building. On the other hand, the louver type window was found to be less effective than any other windows.

• Wind and Structures
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• v.4 no.1
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• pp.31-44
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• 2001

Mean concentrations of ammonia gas released as a tracer from an isolated low-rise building have been measured and predicted. Predictions were calculated using computational fluid dynamics (CFD) and two dispersion models: a diffusion model and a Lagrangian particle tracking technique. Explicit account was taken of the natural variation of wind direction by a technique based on the weighted summation of individual steady state wind direction results according to the probability density function of the wind direction. The results indicated that at distances >3 building heights downstream the weighted predictions from either model are satisfactory but that in the near wake the diffusion model is less successful. Weighted solutions give significantly improved predictions over unweighted results. Lack of plume spread is identified as the main cause of inaccuracies in predictions and this is linked to inadequate resolution of flow features and mixing in the CFD model. Further work on non-steady state simulation of wake flows for dispersion studies is recommended.

• Analytical Science and Technology
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• v.25 no.1
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• pp.14-18
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• 2012

Rn-222 was used as a natural radioactive isotope tracer to evaluate non-aqueous phase liquid(NAPL) contaminated soil and aquifer. In the case of soil sample, Rn-222 concentration was inversely decreased with diesel concentration in the granite soil sample and it was decreased about 30% at the 13% diesel contaminated soil. For evaluating trichloroethylene (TCE) contaminated aquifer, the natural radioisotope Rn-222 was used as naturally occurring partitioning tracer for the approximate localization and semiquantitative assessment of the TCE source zone. Rn-222 was analyzed for the estimation of TCE contamination ranges of the acquifer in the contaminated site at Wonju in Korea.

• Journal of the Korean Geotechnical Society
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• v.20 no.4
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• pp.49-56
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• 2004

Tracer tests were conducted to investigate leachate outflow through damaged parts on HDPE liner subject to puncture loads in a closed landfill. Natural gradient tracer test was used with two different types of tracers, iodide and Rhodamine WT. Tracers were selected under careful consideration of chemical components of leachate. Five injection wells with fourteen detection points were installed and operated throughout the test site. In this study, it is found that Iodide and Rhodamine WT are applicable and effective for leachate leakage investigation on waste landfills. Also, it is concluded that considerable amount of leachate was leaked through the rain water drain box and side wall of drain box.

• Tunnel and Underground Space
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• v.26 no.4
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• pp.274-282
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• 2016

Natural ventilation is employed in limestone mines that have been currently operated in Korea, and there has been a growing issue of a significantly weak airflow caused by the large-scale excavation. Thus, the air quality in the working area is considerably poor. In order to improve this circumstance, it is mainly required to examine ventilation performance. In this study, the examination of ventilation efficiency was conducted by using tracer gas method. The result of this work indicated detailedly the ventilation problems in research mine, in that extremely low air velocity, recirculation, and air change rate were evaluated quantitatively using tracer gas. Therefore the ventilation performance evaluation using tracer gas can be opted as a precise method to improve the working area in mines.

• The Journal of Engineering Geology
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• v.16 no.3 s.49
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• pp.245-254
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• 2006

Using a natural gradient tracer test, the characteristics of hydrodynamic dispersion according to each depth of a fractured rock were studied, and the effective porosity and longitudinal dispersivity of the fractured rock were estimated. The difference of vertical hydrodynamic dispersion was identified by concentration breakthrough curves linear regression analyses of bromide concentrations according to depths versus time, and hydraulic fracture characteristics at two intervals of the monitoring well. Higher concentration and faster arrival time at GL- 18 m depth (RQD 13%, average joint spacing 2 cm, TCR 100%) than at GL- 25 m depth (RQD 41%, average joint spacing 7 cm, TCR 100%) resulted from shorter distance and more fractures. Tracer was transported through the 1 st fractures until the arrival of its peak concentration and through the 2nd fractures or matrix diffusion after the arrival of its peak concentration. The increase/decrease slopes of bromide concentration versus time were 3.46/-1.57 at GL-18 m depth and 3.l9/-0.47 at GL- 25 m depth of the monitoring well. So the faster bromide transport was confirmed at GL- 18 m depth with more fractures. The concentration increment of bromide was fitted by a Gaussian function and the concentration decrement of bromide was fitted by an exponential function. Effective porosity and longitudinal dispersivity estimated by CATTI code were 10.50% and 0.85 m, respectively.