• Journal of Soil and Groundwater Environment
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• v.14 no.6
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• pp.65-70
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• 2009

Reduction of groundwater surface tension prior to air sparging (SEAS, surfactant-enhanced air sparging) was known to increase air saturation in the aquifer under influence, possibly enhancing the removal rates of volatile contaminants. Although SEAS was known to be efficient for increasing air saturation, little information is available for different hydrogeological settings including soil particle sizes and the depth of aquifer. We investigated water saturations in the sparging influence zone during SEAS using one-dimensional column packed with sands of different particle sizes and different aquifer depths. An anionic surfactant was used to suppress the surface tension of water. Two different sands were used; the air entry pressures of the sands were measured to be $15.0\;cmH_2O$, and $36.3\;cmH_2O$, respectively. No significant difference was observed in the water saturation-surface tension relationship for sands with different particle sizes. As the surface tension decreased, the water saturation decreased to a lowest point and then it increased with further decrease in the surface tension. Both sands reached their lowest water saturations when the surface tension was set approximately at 42 dyne/cm. SEAS was conducted at three different aquifer depths; 41 cm, 81 cm, and 160 cm. Water saturation-surface tension relationship was consistent regardless of the aquifer depth. The size of sparging influence zone during SEAS, measured using two-dimensional model, was found to be similar to the changes in air saturation, measured using one-dimensional model. Considering diverse hydrogeological settings where SEAS to be applied, the results here may provide useful information for designing SEAS process.

• Journal of the Korean Geophysical Society
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• v.2 no.3
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• pp.225-233
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• 1999

Electrical resistivity of a rock-sample is dependant on not only formation factor of rock itself but also many parameters such as fluid type, measuring device, temperature, water saturation, electrical contact between electrode and core section, induced polarization, and frequency of electric source. In this study, we attempt to verify various affecting factors in core resistivity measurements and to find a better environment for core resistivity measurement. Particularly great attention has been paid to understanding the effects of temperature, water saturation, contact condition between sample and electrodes, and frequency of electric source. Precise measurement of resistivity can be achieved by utilizing silver paste for better contacts, taping samples for constant moisture contents, and using time-series resistivity data.

• The Journal of Engineering Geology
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• v.14 no.2
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• pp.179-187
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• 2004

This study conducted a laboratory work to determine the change of dielectric constant of saturated soil porous media, which is injecting EML to use Frequency Domain Reflectometry(FDR) system and length 7cm-length measurement sensor. It is purpose of study that estimate a movement path through pore of soil for an ethanol mixing liquid(EML) which have the same specific gravity of water at $20{\;}^{\circ}C$, and determine to a dielectric measuring range for the measurement sensor. As an outflow point of saturated soil column upper part recedes from an EML inject point in EML diffusion test, the diffusion extent of EML through pore of saturated soil was expanded. And results of ail EML flow experiment were measured the change of dielectric constant at all measurement sensors which are placed to constant interval at the same travel time for saturated soil column. Therefore, the displace process of water that exist in pore of saturated soil by EML injection is enough available and confirm together mobility through pores.

• Journal of the Korea institute for structural maintenance and inspection
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• v.24 no.1
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• pp.142-147
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• 2020

This study investigates the effects of moisture content on diffuse ultrasound to be applied for the evaluation of micro-structural damage in concrete subjected to various environmental conditions. We monitored diffuse wave parameters for concrete samples in process of water saturation for 5 days. Dried samples were immersed in a water bath, and the change of moisture content in concrete were estimated by measuring the change of mass. For the diffuse wave analysis, a frequency range of 500 kHz, which represents a scattering regime of ultrasound in concrete, was selected. The test results reveal that the ultrasonic diffusivity slightly changed, and the ultrasonic dissipation significantly increased by approximately 120% in the process of water saturation. Therefore, the moisture content in concrete should be considered for the evaluation of micro-structural damage using diffuse wave techniques.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2003.04a
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• pp.168-171
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• 2003

연속주입추적자시험이 실시된 현장사이트의 규모는 4.5m$\times$4.5m$\times$6.0m 정도이다. 시험 사이트내에서 실시된 추적자시험은 주입공(Pl)에서 Rhodamine WT 50ppm 용액을 1.8$\ell$/min의 주입율로 6일 동안 연속적으로 주입함과 동시에 관측공(P2, P3, Il, I2, I3)에서 일정한 시간간격으로 지하수를 채수하여 추적자농도를 산출하였다. 시험결과, 지하수면 하부를 포함하는 관측공(P2, P3)의 최대추적자농도는 초기주입농도의 10% 정도이며, 지하수면 상부에 위치한 지하수공(Il, I2, I3)들에서의 최대추적자농도는 초기농도의 75% 정도로서 추적자의 농도차이가 상대적으로 매우 크게 나타났다. 본 연구에서는 자유면대수층내에서 포화대를 포함한 관측공과 비포화대만을 포함한 관측공에서의 수리분산특성에 대해 비교.분석한 결과, 오염물이 연속적으로 토양에 유입되는 경우 비포화대 구간에서는 이류기작에 의한 농도희석이 거의 없으므로 오염물농도가 매우 클 것으로 판단된다.

• The Journal of Engineering Geology
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• v.16 no.3 s.49
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• pp.301-306
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• 2006

Damages of cultural properties is caused by subsidence of foundation relating stone structures. To prevent of these structures, ground monitoring should be achieved certainly. Representative ground subsidence cause is saturated and unsaturated condition that is produced repeatedly by groundwater level fluctuations. It controls role that decrease porosity or effective porosity of soil media. Estimation of physical properties can predict from reaction of dielectric constant. Variations of dielectric constants are measured from physical characteristics change of pore, soil particle, air and water which are consisted to ground. Therefore, ground subsidence monitoring is thought that quantitative measurement is available using dielectric response of media.

• The Journal of Engineering Geology
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• v.14 no.3 s.40
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• pp.301-311
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• 2004

This study is suggested a new dielectric tracer test method to understand geological structure of porous media and groundwater flow to use the dielectric constant which is one of electrical special quality of various geological materials. To measure their parameters, tracer material is made an ethanol mixing liquid(EML) having a same specific gravity of water. Also, soil materials are prepared a dielectric tracer test using the FDR system that could measure dielectric constant for saturated standard sand and river sand layers which have different initial porosity. To compare with their results, we discussed with the concentration variation of saline water having a saline concentration $3\%$ which is general tracer material by using the electro multi-meter system in the laboratory or field test. In two tracer experiment results, EML tracer test could confirm definitely EML concentration variation from each saturated soil layer as standard and river sands. However, tracer test of saline water $3\%$ concentration could not confirm permeating movement of water by degree of salinity change because these are settled at lower part column in a whole column area continuously. These causes are that specific gravity of saline water is heavier than water. That is, it could know that deposition of saline water is composed of lower part of soil column continuously independently of the direction of water into saturated soil material.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2003.04a
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• pp.263-267
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• 2003

물만 주입한 1군과 물-토양을 주입한 2군, 물-ORC를 주입한 3군, 물-토양-ORC를 전부 주입한 4군의 4개군으로 조건을 차별화하여 2$0^{\circ}C$ 항온 OER시험을 실시하였다. 1군은 약4mg/L, 2군은 3mg/L, 3군은 12~13mg/L, 4군은 11~12mg/L의 DO를 나타내었다. ORC를 투여하지 않은 1군과 2군은 2$0^{\circ}C$ 용존산소 포화선인 Bmg/L에 크게 못미치는 것으로 나타났고 ORC를 투여한 3군과 4군은 포화선보다 3~4mg/L 높은 수치를 나타내었다. 토양을 주입한 2군과 4군에서는 토양 미생물의 영향을 받아 DO가 감소하나 ORC를 투입한 4군에서는 그 영향이 미미하게 나타난다. TCE 분해능 시험은 15$^{\circ}C$에서 항온으로 30일간 시험하였다. 초기 농도 5000ppb가 30일 경과 후 약 4000ppb로 약20%의 분해율을 나타내었고, 메탄을 첨가했을 때 더 잘 분해됨을 보여주었다.

• The Korean Journal of Rheology
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• v.9 no.4
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• pp.190-199
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• 1997

단열용도의 폴리우레탄 미세포 포움의 가공에 대한 연구를 수행하였다. 미세포 구조 를 얻기 위해서는 핵생성율을 증진시키고 균일한 분포의 기포를 생성시켜야 한다. 이를 위 해 이산화탄소 기체를 풀리올과 이소시아네이트에 각각 과포화시키고 충돌혼합하여 초음파 가진을 적용하였다. 이산화탄소 기체가 수지 내부에서 기포 내부로 확산함에 따라 기포의 성장이 조절된다고 가정하고 금형이 충전되는 동안에 금형 내부에서의 기포성장기구를 이해 하기 위하여 수치적인 방법으로 이론적 연구를 수행하였다. 경화 시간과 확산 경계를 고려 하여 최종적인 기포의 크기를 계산하였으며 반응속도론을 고려하여 중합반응동안의 폴리우 레탄의 점도의 변화를 예측하고 경화 시간을 결정하였다. 실험적으로 결정된 기체 분자수를 기준으로 하여 이론적으로 확산경계를 예측하였다. 화학적 발포제인 물과 함께 물리적 발포 제인 이산화탄소를 각각 1,2,3기압의 포화압력으로 변화시키면서 폴리올과 이소시아네이트에 포화시켜 폴리우레탄 포움을 제작하고 제작된 포움의 밀도, 열전도도, 및 기포의 수와 지름 을 측정하였다. 측정된 결과로부터 이산화탄소의 포화압력과 초음파 가진이 포움의 기포핵 생성에 미치는 영향을 살펴보았다.

• Journal of the Earthquake Engineering Society of Korea
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• v.8 no.2
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• pp.1-8
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• 2004

Sliding mode control (SMC), which is one of active control algorithms showing remarkable control performance, requires the excessive control force for control of seismically excited civil structures. Therefore, controller saturation should be considered in design of SMC. In this study, a method for determining the maximum control force is developed in terms of the fraction of the lateral restoring force using a design response spectrum. Numerical analyses of MDOF structures with one or multiple control devices verify the effectiveness of the proposed method for the control of seismically excited civil structures with saturation problem.