• Proceedings of the KIEE Conference
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• 2004.11a
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• pp.110-111
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• 2004

본 논문은 부분방전 검출 시험 전에 수행하는 Calibration 신호 주입 및 검출 방법에 대한 연구이다. 사용된 시료는 지중케이블의 절연층으로 사용되는 XLPE 시트와 XLPE케이블이다. 실험방법은 50kV 내전압기(750-2CTS, Hipotronics)로부터 공급된 Calibration 신호를 Lemke (LDP-5, LDIC), 오실로스코프 (TDS-3012, Tektronix)와 주파수 분석기 (8563E, HP)를 사용하여 측정하였다. 시험에 사용된 센서로는 자체 제작한 박전극센서, UHF 센서 그리고 Lemke UHF 센서를 사용하였다. 위 방법을 통해 신호의 형태와 인가 전하량에 따른 Calibration 파형과 전하량 변화를 비교하였다. 실험결과 Calibration 신호 주입시 시험 환경 및 센서에 따라 Calibration 신호와 주입방법의 차이가 발생하였다.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.11a
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• pp.316-318
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• 2004

본 논문은 부분방전검출 시험 전에 수행하는 Calibration 신호 주입 및 검출 방법에 대한 연구이다. 사용된 시료는 활선상의 배전용 XLPE 케이블이다. 실험방법은 50kV 내전압기 (750-2CTS, Hipotronics)로부터 공급된 Calibration 신호를 Lemke (LDP-5, LDIC), 오실로스코프 (TDS-3012, Tektronix)와 주파수 분석기 (8563E, HP)를 사용하여 측정하였다. 마지막으로 시험에 사용된 센서는 안테나 특성의 UHF 센서와 고주파 특성의 HFCT 센서이다. 실험결과, Calibration 신호 주입 시 시험 환경 및 센서에 따라 Calibration 신호와 주입방법의 차이가 발생하였다. 따라서 신호의 형태와 인가 전하량에 따른 Calibration 파형과 전하량 변화를 알 수 있었다.

• Journal of Korean Tunnelling and Underground Space Association
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• v.21 no.4
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• pp.545-560
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• 2019

During EPB TBM tunnelling, an appropriate application of additives such as foam and polymer is an essential factor to secure the stability of TBM as well as tunnelling performance. From the '90s, there have been many studies on the optimal injection of additives worldwidely contrary to the domestic situation. Therefore, in this paper, the foam, which is widely adopted for soil conditioning, was selected as an additive in order to investigate the effect of foam injection on TBM performance through a series of laboratory excavation tests. The excavation experiments were carried out on artificial sandy soil specimens with consideration of the variance of FIR (Foam Injection Ratio), FER (Foam Expansion Ratio) and $C_f$ (Surfactant Concentration), which indicate the amount and quality of the foam. During the tests, torque values were measured, and the workability of conditioned soil was evaluated by comparing the slump values of muck after each experiment. In addition, a weight loss of the replaceable aluminum cutter bits installed on the blade was measured to estimate the degree of abrasion. Finally, the foam injection ratio for the optimal TBM excavation for the typical soil specimen was determined by comparing the measured torque, slump value and abrasion. Note that the foam injection conditions satisfying the appropriate level of machine load, mechanical wear and workability are essential in the EPB TBM operational design.

• Journal of the Korean Vacuum Society
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• v.4 no.2
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• pp.183-188
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• 1995

고에너지(50-200KeV)로 가속된 이온을 모재표면에 물리적으로 투입하므로써 표면의 조성 및 조직을 변화시키는 공정인 이온주입기술을 이용하여 경량고강도소재로 각광받고 있는 AI2218 합금의 재식성 향상을 연구하였다. 질소이온주입은 DuoPIGatron 이온원을 사용하여 가속전압 100KeV, 조사량 $1{\times}10^{17}ions/\textrm{cm}^2$~$5{\times}10^{17}ions/\textrm{cm}^2$의 조건으로 행하였으며 AI합금의 열화를 방지하기 위하여 시편온도를 $60^{\circ}C$이하로 유지하였다. 질소이온 주입재의 재식성 평가를 위하여 3.5% NaCI 용액에서 양극분극시험 및 5% NaCI 용액에서 염수분무시험을 행하였다. Auger Electron Spectroscopy와 Transmission Electron Microscopy을 이용하여 표면의 질화물형성 여부를 조사하였으며, Scanning Electron Microscopy을 이용하여 부식된 표면을 관찰하였다. AI2218합금에 질소이온을 주입한 결과 표면에 미세한 AIN 석출물을 형성하였으며 이러한 질화물형성에 의해 공식(pitting)발생을 억제하고 부식전류밀도를 감소시켜 내식성이 향상되었다.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.39 no.6
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• pp.779-788
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• 2019

The compaction grouting method is one of the conventional ground improvement methods, which consolidates and compacts the surrounding ground through the injection of grout materials with low mobility. Injecting the grout into the ground can improve the soil properties, as well as form a composite of soil-grout columns. However, the conventional grout pumping is not applicable to handle multiple injection holes at the same time, which may diminish its constructability when the construction time is not enough. This paper proposes a simultaneous multiple compaction-grouting method using a new pump system developed to cover up simultaneously three injection holes at a time. Field injection tests with a single injection hole and with triangular arrangement of injection holes were conducted to evaluate the applicability of the proposed method to soft clay ground. In addition, a series of standard penetration tests (SPTs) were performed to assess the efficiency of each arrangement in improving the soft ground. It is noted from the in-situ test results that the interval distances between injection holes and the elapse time for ground stabilization are the crucial factors governing the applicability of the simultaneous multiple compaction-grouting method to improve the soft clay ground.

• Proceedings of the Korea Water Resources Association Conference
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• 2020.06a
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• pp.290-290
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• 2020

연구지역인 충청남도 홍성군 갈산면 신곡마을은 상시 가뭄지역으로서 농번기 물부족을 겪고 있으며, 물 확보의 수단으로서 지하수 인공함양이 고려되고 있다. 본 연구에서는 수치모델을 이용하여 수직정 방식의 지하수 인공함양시 주입 효과를 예비 평가하였다. 모델 지역은 가로 세로 2,450 × 2,350 m로서 10 × 10 m 간격의 격자로 구성하였으며, 현장에서 실시된 지하수위 조사 및 9공의 시추조사, 1개공의 양수시험 결과로부터 수리전도도, 지층분포 등을 구성하였다. 정류모델결과, 실측 및 예측 지하수위의 표준오차(Standard error of the estimate)는 0.53 m, 표준화제곱근오차(Normalized RMS)는 6.79%, 상관계수는 0.99%로 나타났다. 수직정을 통한 주입 효과를 평가하기 위하여, 주입량을 5 ㎥/d, 10 ㎥/d, 15 ㎥/d, 20㎥/d, 주입기간을 1일, 3일, 7일, 우물의 개수를 1개, 3개, 5개일 때 등 다양한 조건하에서의 부정류 모델을 수행하였다. 이로부터 주입의 효과인 지하수위 상승량 및 상승 범위 등을 토대로 물 부족 기간의 인공함양 시나리오(주입정의 위치, 갯수, 심도, 기간 등)를 예비적으로 제시하였으며, 추후 정밀 모델 및 실제 현장 주입 시험 등을 토대로 인공함양 설계를 추진할 예정이다.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2004.04a
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• pp.63-66
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• 2004

폐기물매립장에서의 침출수 유출을 확인하고 경로를 파악하기 위해 추적자시험이 실시되었다. 추적자는 요오드와 Rhodamine WT를 이용하였으며, 추적자는 T-2, 4, 5공에서 주입하였다. 관측지점으로는 매립장내 우수관 출구와 측면배수구에서 모니터링 하였으며, 또한 주입공 하부의 9개 지하수공에서 모니터링 하였다. T-4, T-2와 T-5 지하수공에서 요오드와 Rhodamine WT 용액을 주입한 추적자시험 결촤 매립장의 바닥 차수막이 파손되어 침출수가 우수관내로 유출되고 있음이 입증되었으며, 또한 매립장내의 투수성이 매우 높아 일반적인 자연상태에 비해 매립장에서 우수관내로의 침출수 유입이 매우 빠름을 알 수 있었다. T-4와 T-2 지하수공에서 실시된 추적자시험에서 매립장의 차수벽 하부에 위치한 B-5와 B-6공에서 다량의 추적자가 관측되어 하부차수벽을 통해 침출수가 유출되고 있음이 확인되었다. 본 현장에서 실시된 추적자시험을 통해 매립장에서의 침출수 유출은 매우 빠른 속도로 발생하고 있으며, 또한 주 유출경로로는 T-4와 T-5 지하수공 주변의 바닥차수막과 매립장의 하부차수벽을 통해 유출 되어지고 있음을 확인할 수 있었다.

• The Journal of Engineering Geology
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• v.25 no.2
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• pp.215-225
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• 2015

We performed injection tests in a deep-seated confined aquifer to assess the potential of artificial recharge as a means of preventing saltwater contamination, thereby securing groundwater resources for the Nakdong Delta area of Busan City, Korea. The study area comprises a confined aquifer, in which a 10-21-m-thick clay layer overlies 31.5-36.5 m of sand and a 2.8-11-m-thick layer of gravel. EC logging of five monitoring wells yielded a value of 7-44 mS/cm, with the transition between saline and fresh water occurring at a depth of 15-38 m. Above 5 m depth, water temperature is 10-15.5℃, whereas between 5 and 50 m depth the temperature is 15.5-17℃. Approximately 950 m³ of fresh water was injected into the OW-5 injection well at a rate of 370 m³/day for 62 hours, after which the fresh water zone was detected by a CTD Diver installed at a depth of 40 m. The persistence of the fresh water zone was determined via EC and temperature logging at 24 hours after injection, and again 21 days after injection. We observed a second fresh water zone in the OW-2 well, where the first injection test was performed more than 20 days before the second injection test. The contact between fresh and saline water in the injection well is represented by a sharp boundary rather than a transitional boundary. We conclude that the injected fresh water occupied a specific space and served to maintain the original water quality throughout the observation period. Moreover, we suggest that artificial recharge via long-term injection could help secure a new alternative water resource in this saline coastal aquifer.

• Geophysics and Geophysical Exploration
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• v.10 no.4
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• pp.353-360
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• 2007

We practiced fresh water injection test to identify its applibility as a method of seawater intrusion mitigation technique, and monitored the change of borehole fluid conductivity and the behavior of injected fresh water using borehole multichannel electrical conductivity monitoring and well-logging, and DC resistivity and SP monitoring at the surface. Well-logging and multichannel EC monitoring showed the decrease of fluid conductivity due to fresh water injection. We note that such an injection effect lasts more than several month which means the applibility of fresh water injection as a seawater intrusion control technique. Although SP monitoring did not show meaningful results because of weather condition during monitoring and the defects of electrodes due to long operation time, DC resistivity monitoring showed its effectiveness and applicability as a monitoring and assessment techniques of injection test by means of imaging the behavior and the front of fresh water body in terms of the increase of resistivity with reasonable resolution. In conclusion, we note that geophysical techniques can be an effective method of monitoring and evaluation of fresh water injection test, and expect that fresh water injection may be an practical method for the mitigation of seawater intrusion when applied with optimal design of injection well distribution and injection rate based on geophysical evaluation.

• The Journal of Engineering Geology
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• v.31 no.4
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• pp.589-601
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• 2021

Artificial recharge technology is a method for solving problems such as groundwater level drop and ground subsidence caused by groundwater withdrawal. This study investigated the applicability of using the hydraulic conductivity of an aquifer to predict injection test results for aquifer restoration. Pumping and injection tests were performed under the same conditions as those for the artificial injection facility located in Icheon, Gyeonggi-do. The hydraulic conductivity of the aquifer, which plays a decisive role in restoring the groundwater level, was derived from the pumping test. A numerical model of a simplified on-site aquifer was constructed, and a transient analysis was applied with the same conditions as the pumping test. The correlation between the measured and the resulting model values is strong (R² = 0.78). The injection test was performed in a sedimentary layer composed of silt sand and clay sand. From the results of the injection test, an empirical formula was derived using Theim's formula, which is a common well analysis solution to determine the parameters of the aquifer from time-level data. The model values from the empirical formula have a high degree of correlation (R² = 0.99) with measured values. Under specific conditions, for areas where it is difficult to conduct an injection test, the formula from this study, which relies on the hydraulic conductivity of the aquifer determined through the pumping test, may be used to predict reliable injection rates for groundwater restoration.