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

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
• /
• 2002.09a
• /
• pp.343-346
• /
• 2002

인공함양 특성평가를 위한 동위원소기술을 적용하기 위한 연구지역으로 영남내륙권의 고령군과 달성군의 경계에 위치한 낙동강변의 강변여과수 개발지역을 선정하였으며, 동위원소기술적용을 위하여 연구지역내에 위치한 강변여과수 개발을 위한 양수정과 주변공들 및 지표수들에 대한 시료채취를 수행하였다. 관측공 중 한 공에 대하여는 다중패커시스템 (Multi-packer system)을 활용하여 심도별 변화를 살펴보았다. 연구지역내 물시료들에 대한 현재까지의 산소와 수소 동위원소 및 삼중수소 함량 분석결과는 다중패커설치공 및 일반 관측공과 지표수들간에 서로 중첩되어 구분이 어렵다. 스트론튬 동위원소비는 양수정 및 그 인접공의 시료들과 강변에서 인접한 공의 시료들간에 차이는 있으나 명확하지는 않다. 질소동위원소 분석결과를 살펴보면 전반적으로 화학비료로나 토양내의 유기물로부터 유래한 것으로 해석할 수 있다. 이처럼 현재까지의 기초분석 결과는 자연수 시료들에 적용된 다양한 동위원소값들이 서로 유사한 값들을 보여서 동위원소 특성을 지하수 유동특성이나 함양특성을 해석하기 위한 추적자로 이용하는데 어려움이 있을 것으로 판단된다. 따라서 특정한 시기의 강우사건에 대해 강수, 낙동강물, 양수정 및 일련의 주변공과 다중패커시스템이 설치된 공의 심도별 구간 등에 대해 현재보다 보다 집중적이고 체계적인 시료채취가 시도되어지거나 방사성동위원소를 이용한 추적자 시험이 병행되어야 할 것으로 사료된다.

• Journal of Soil and Groundwater Environment
• /
• v.11 no.6
• /
• pp.53-60
• /
• 2006

Single well injection withdrawal tracer tests with bromide were carried out at two wells developed in a horizontally heterogeneous fractured rock. The hydraulic conductivity of TW-1 well was 5 times larger than TW-2 well, and the average linear velocity of TW-2 well was 1.8 times faster than TW-1 well. The difference of hydrodynamic dispersions of two wells in the fractured rock was studied with the analysis of concentration breakthrough curves and cumulative mass recovery curves of bromide with withdrawal time, and the estimation of average travel distance, pore velocity, longitudinal dispersivity and longitudinal dispersion coefficient. The average travel distances of bromide were estimated to be 3.00 m in TW-1 well and 5.62 m in TW-2 well. The average pore velocities for the injection/withdrawal phase were estimated to be $4.31\;{\times}\;10^{-4}\;m/sec$ in TW-1 well and $8.08\;{\times}\;10^{-4}\;m/sec$ in TW-2 well. Average travel distance and pore velocity were higher in TW-2 well because of small effective porosity. Longitudinal dispersivities were estimated to be 28.73 cm in TW-1 well and 18.49 cm in TW-2 well, and bromide transport was 1.55 times faster in TW-1 well. Longitudinal dispersion coefficients were estimated to be $5.14\;{\times}\;10^{-6}\;m^2/sec$ in TW-1 well and $6.06\;{\times}\;10^{-6}\;m^2/sec$ in TW-2 well, and diffusion area was 1.18 times larger in TW-2 well.

• Proceedings of the Korean Radioactive Waste Society Conference
• /
• 2007.11a
• /
• pp.181-182
• /
• 2007

• Proceedings of the Korea Water Resources Association Conference
• /
• 2017.05a
• /
• pp.466-466
• /
• 2017

지하공간의 개발과 지하공간의 굴착으로 인한 지표수 및 지하수 시스템의 변화나 굴착면 주위의 지하수 유동 체계의 변화는 터널내로의 지하수 유입, 지표수 고갈을 가져온다. 또한 터널 상부의 지반에서 현지응력의 변화로 인한 지하수 유출은 지표침하, 하천수 및 계곡수 고갈을 발생시킬 수 있다. 그러나, 터널설계 시 비용 및 시간, 현장의 진입조건 등의 제약으로 상세한 지반조사의 실시가 이루어지지 않을 때가 있다. 또한, 터널 공사가 진행되는 중에는 공사기간과 공사비 때문에 별도의 지반조사를 하지 않는다. 그 대신에 터널 막장에서 실시하는 Face Mapping을 토대로 공사를 진행하며, 대규모 위험요소가 발견되지 않는 이상 별도의 비용과 시간을 투입하여 추가 지질 및 지반 조사를 실시하는 경우는 매우 드물다. 연구지역의 지질은 경상분지내 백악기 하양층군의 퇴적암류, 이를 관입/분출한 불국사화강암류 및 제3기 화산암류, 전기 에오세 연일층군에 대비되는 퇴적암류로 구성되어 있다. 이들을 피복하는 제4기 충적 퇴적층은 주로 단층곡과 동측 지괴의 선상지 및 하천을 따라 분포한다. 연구지역에는 폭 100 m 이상의 대규모 단층대가 발달하였으며 제4기 단층운동으로 인한 단층파쇄대가 존재한다. 퇴적암 분포지역에서는 반복층서가 관찰되며 소규모 단층, 단열, 변형띠 등이 연속적으로 발달해 있다. 본 연구에서는 터널공사에 의한 지하수 변화를 확인하기 위하여 현장추적자 시험과 수질분석 및 지하수 모델링을 실시하였다. 현장 수질 분석에 의한 지표수와 지하수 간의 수질의 차이를 보면, 알칼리도를 제외한 대부분의 수질 항목이 서로 유사성을 보인다. 전기전도도(EC), TDS, 알칼리도의 경우 지표수의 수원지에서 터널 내부로 유입이 일어나고 있다. 이는 터널 공사의 영향으로 판단되며, 현장에서 실시한 추적자 시험에서는 추적자의 이동 시간이 매우 빨라 지표 수원지로부터 지표수가 터널내부로 빠른 속도(10시간 이내)로 유입된다고 판단된다. 지하수 모델링 결과, 정상류 상태에서는 지하수가 북동쪽의 높은 고도에서 서남쪽의 낮은 고도로 흐르는 것으로 확인되며, 가뭄시에도 지하수 함양으로 지하수가 고갈되지는 않는 것으로 나타났다. 부정류 상태 모델링 결과, 일일 평균 $32.49m^3$의 지하수가 터널 내부로 유입되는 것으로 산정되었다. 이 양은 터널 내부뿐만 아니라 터널 공사 현장 주위로도 지하수 유출이 일어나고 있음을 지시한다.

• The Journal of Engineering Geology
• /
• v.17 no.1 s.50
• /
• pp.41-47
• /
• 2007

Geotechnical Phenomena such as landslide, groundwater recharge and groundwater fluctuation due to rainfall can be explain to use a dielectric response and infiltration variation by the movement of a wetting front in the subsurface. The infiltration of a wetting front is infiltrating to the connected pores which are distributed in unsaturated soil. In this study we carried out to laboratory experiment of a vertical infiltration column test using ethanol mix-ing tracer which has same the specific gravity of water. All physical values are detected to use a variation of dielectric constant and calculated to use a dielectric mixing model and tracer test model. This dielectric method measured by each dielectric constant of geological soil porous materials should be of for the geotechnical information and useful a field monitoring technique for detecting the variations of the volumetric water content and the wetting front, which are insignificant the key parameter to understanding the landslide by rainfall.

• Journal of Internet Computing and Services
• /
• v.6 no.1
• /
• pp.1-12
• /
• 2005

Recently, the patterns of cyber attack through internet have been various and have become more complicated and thus it is difficult to detect a network intruder effectively and to response the intrusion quickly. Therefore, It is almost not possible to chase the real location of a network intruder and to isolate the Intruder from network in UDP based DoS or DDoS attacks spoofing source IP address and in TCP based detour connection attacks. In this paper, we propose active security architecture on active network to correspond to various cyber attacks promptly. Security management framework is designed using active technology, and security control mechanism to chase and isolate a network intruder is implemented. We also test the operation of the active security mechanism implemented on test_bed according to several attack scenarios and analyze the experiment results.

• Tunnel and Underground Space
• /
• v.33 no.5
• /
• pp.388-398
• /
• 2023

The changes in groundwater flow due to mining development act as a contributing factor to major issues such as ground subsidence, strength reduction and collapse. For the sustainable mining development, measures for dealing with fluctuations in seasonal underground water inflow, power losses, pump damage, and unexpected increases in inflow must be put in place. In this study, the aim is to identify the causes of underground seepage through the examination of hydrological connectivity between the study area and nearby limestone mine. A tracer tes for assessing subsurface connectivity has been planned. A variety of tracers, such as dyes and ions, were applied in lab test to select the optimal tracer material, and a hydrological model of the study area was implemented through field test. Finally, the hydrological connectivity between the external stream and underground water in the mine was analyzed.

• Journal of the Korean Society of Manufacturing Process Engineers
• /
• v.16 no.2
• /
• pp.22-27
• /
• 2017

During the water treatment process for household water supply, a reservoir is the last place the water is stored before being supplied to users, and the duration of the water's stay is an important factor that affects its safety. This may cause the concentration of the residual chlorine disinfectant to increase and thus lower the water's quality. The concentration and discharge efficiency of residual chlorine must be verified and managed, because these are key factors that affect the reservoir's performance. Because the actual verification test for analyzing the efficiency of a reservoir and the disinfectant's dilution capacity is difficult, simulations are generally conducted using the computational fluid analysis method. However, the simulation results require validation with experiments. The error and drainage efficiency were analyzed in this study by comparing and analyzing the actual tracer test and simulation so that the actual test for a hexagonal drainage can be replaced by the computational fluid analysis method. Based on the results of the efficiency analysis, the hexagonal reservoir was found to be appropriate, and the simulation's reliability was verified with a tracer test.

• Journal of Korea Water Resources Association
• /
• v.43 no.2
• /
• pp.153-165
• /
• 2010

Large-Scale Particle Image Velocimetry (LSPIV) is an extension of particle image velocimetry (PIV) for measurement of flows spanning large areas in laboratory or field conditions. LSPIV is composed of six elements - seeding, illumination, recording, image transformation, image processing, postprocessing - based on PIV. Possible error elements at each step of Mobile LSPIV (MLSPIV), which is a mobile version of LSPIV, in field applications are identified and summarized the effect of the errors which were quantified in the previous studies. The total number of elemental errors is 27, and five error sources were evaluated previously, seven elemental errors are not effective to the current MLSPIV system. Among 15 elemental errors, four errors - sampling time, image resolution, tracer, and wind - are investigated through an experiment at a laboratory to figure out how those errors affect to velocity calculation. The analysis to figure out the effect of the number of images used for image processing on the velocity calculation error shows that if over 50 images or more are used, the error due to it goes below 1 %. The effect of the image resolution on velocity calculation was investigated through various image resolution using digital camera. Low resolution image set made 3 % of velocity calculation error comparing with high resolution image set as a reference. For the effect of tracers and wind, the wind effect on tracer is decreasing remarkably with increasing the flume bulk velocity. To minimize the velocity evaluation error due to wind, tracers with high specific gravity is favorable.