Sangki Kwon
Inha University
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Publication
Featured researches published by Sangki Kwon.
Nuclear Engineering and Technology | 2013
Sangki Kwon; Won-Jin Cho; Jae-Owan Lee
Adequate design of engineered barriers, including canister, buffer and backfill, is important for the safe disposal of high-level radioactive waste. Three-dimensional computer simulations were carried out under different condition to examine the thermal and mechanical behavior of engineered barriers and rock mass. The research looked at five areas of importance, the effect of the swelling pressure, water content of buffer, density of compacted bentonite, emplacement type and the selection of failure criteria. The results highlighted the need to consider tensile stress in the outer shell of a canister due to thermal expansion of the canister and the swelling pressure from the buffer for a more reliable design of an underground repository system. In addition, an adequate failure criterion should be used for the buffer and backfill.
Nuclear Engineering and Technology | 2012
Sang Hyuk Bang; Seokwon Jeon; Sangki Kwon
A three-dimensional discrete fracture network model was developed in order to simulate the hydraulic characteristics of a granitic rock mass at Korea Atomic Energy Research Institute (KAERI) Underground Research Tunnel (KURT). The model used a three-dimensional discrete fracture network (DFN), assuming a correlation between the length and aperture of the fractures, and a trapezoid flow path in the fractures. These assumptions that previous studies have not considered could make the developed model more practical and reasonable. The geologic and hydraulic data of the fractures were obtained in the rock mass at the KURT. Then, these data were applied to the developed fracture discrete network model. The model was applied in estimating the representative elementary volume (REV), the equivalent hydraulic conductivity tensors, and the amount of groundwater inflow into the tunnel. The developed discrete fracture network model can determine the REV size for the rock mass with respect to the hydraulic behavior and estimate the groundwater flow into the tunnel at the KURT. Therefore, the assumptions that the fracture length is correlated to the fracture aperture and the flow in a fracture occurs in a trapezoid shape appear to be effective in the DFN analysis used to estimate the hydraulic behavior of the fractured rock mass.
Nuclear Technology | 2012
Won-Jin Cho; Sangki Kwon
The effects of the resaturation process occurring in the buffer on the analysis of temperature distribution in the engineered barrier system of a nuclear waste repository were assessed. The assessment was performed using the TOUGH2 computer code, which analyzes the multidimensional fluid and heat flows of the multiphase, multicomponent fluid mixture in an unsaturated medium. The hydraulic and thermal properties of the buffer, backfill, and near-field rock were measured and were used as input parameters for the analysis. If the resaturation process is considered in the thermal analysis, the disposal density of nuclear waste can be increased up to 30% under the given thermal constraint and site condition. The hydrostatic pressure in the near-field rock will not have an important impact on the resaturation process.
Journal of Korean Society for Rock Mechanics | 2013
Chan-Hoon Yoon; Young-Chul Choi; Sangki Kwon; Heui-Joo Choi
Abstract In this study, the thermal analysis is carried out for a result of borehole heater test using ABAQUS ver 6.10 based on finite element analysis code. Thermal-mechanical rock properties as determined by laboratory tests before the in situ test and characteristics of the atmosphere at the test section are used as the initial condition. When comparing the results of the in situ test and thermal analysis, the temperature of C3 observation hole that is 0.9 m away from the heater showed very similar patterns and figures (about 1.3℃ difference). But the results of the A and B observation hole showed a significant difference around 15℃~20℃. To find the reason for these results, the over-coring is carried out for the A1 and B1 observation holes. As a result of checking the excavated rock core with the naked eye, there is no problem on the number and position of the sensor as the test plan. However the state of cement injection in the observation hole is poor. Key words KURT, BHT, Thermal analysis, Over-Coring, Rock mass temperature초 록 본 연구에서는 시추공히터시험의 실측 결과를 FEM 해석코드인 ABAQUS ver 6.10을 이용하여 열 해석을 수행하였다. 현장시험 전 암석 코아에 대한 실내 실험을 통해 결정된 열 , 역학적 암반물성과 실험구간 내 대기특성을 해석 초기조건으로 입력하였다 . 현장시험과 열 해석의 결과를 비교했을 때 , 히터로부터 0.9 m 이격된 C3 관측공의 온도는 상당히 유사한 패턴과 수치 (약 1.3℃ 차이)를 보였으나, A와 B 관측공의 현장시험 결과와는 최대 15℃~20℃ 가량의 큰 차이를 나타냈다 . 이러한 결과의 이유를 찾고자 A1과 B1 관측공을 대상으로 over-coring 을 실시하였다. 육안으로 시추된 코어를 확인한 결과, 센서의 위치, 개수는 문제가 없었지만, 관측공 내 시멘트의 주입 상태가 불량하였다 . 핵심어 지하처분연구시설, 시추공히터시험, 열 해석, 오버코어링, 암반온도
Geosystem Engineering | 2012
Sangki Kwon; Chang-Soo Lee; Seokwon Jeon
Korea participated in DECOVALEX-2011, which is an international cooperation project for enhancing the reliability of computer simulations under the conditions of radioactive waste repositories, and modeled the laboratory compression tests and the in situ Äspö pillar stability experiment (APSE). From the comparison of the results with foreign research teams, it was possible to enhance the reliability of the computer simulation of the complex thermo-mechanical (TM) coupling behavior of rock mass. It was found that the two-step simulation with a full model and a submodel using FLAC3D was effective to combine the influence of in situ stress, tunnel excavation, deposition hole drilling, confining pressure, and thermal loading all together. One of the important results was the estimation of spalling strength of Äspö granite as 120 MPa after comparing the notch depth, notch length, and breakout angle of the notch with actual observation.
Journal of Korean Society for Rock Mechanics | 2014
Jin Heo; Jae Chul Lee; Jung Bum Seo; Seung Hun Park; Jung Chan Park; Sangki Kwon
It is well known that rock properties can be affected by loading in underground condition. In the case of flooded underground mine or tunnels, rock properties variation due to loading might be different from the loading in dry condition. In order to verify the influence of saturated loading condition on rock properties, various laboratory tests had been carried out. Loading on the rock specimen was controlled to be ranged in between 20 ~ 80% of UCS. By comparing the variation of thermal, mechanical, and physical properties of rock specimens under the same load in saturated and dry condition, it was possible to find that the rock properties can be more significantly disturbed in the saturated loading condition than in dry loading condition.
Geosystem Engineering | 2013
Sangki Kwon
The understanding of time-dependent deformation of rock around underground excavations becomes more and more important with the increase in overburden stress, opening size, and temperature expected in deep underground facilities for various purposes. It is desirable to use in situ measurements instead of laboratory data, because of the difference in time-dependent deformation mechanisms observed in laboratory and in situ measurement. In this study, the deformation measurements from Waste Isolation Pilot Plant, which is a deep underground radioactive waste repository in rock salt and a salt mine, in which yield pillar mining design was adopted, were extensively analyzed. It was possible to determine that the transition time from the primary to the secondary creep stages was around 200–300 days. The influence of adjacent excavation on the deformation measurement could be clearly observed. It was also found that the measuring time interval was important to understand the time-dependent deformation mechanisms.
Geosystem Engineering | 2018
Seung-Hun Park; Jin-Seup Kim; Sangki Kwon
Abstract An excavation damaged zone (EDZ) caused mainly by blasting is an important parameter for making reliable evaluations of the overall tunnel stability. Around a blasted tunnel, various rock properties are changed in the EDZ, which is dependent on the original rock properties, blasting design, and tunnel geometry. In this paper, the development of an EDZ and its influence on the mechanical behavior around an underground excavation were investigated using an in situ test and computer simulations. The variation of the rock properties in the EDZ was predicted by considering the blast design and compared with actual measurements using the Goodman jack test. The extent of the EDZ could be calculated from the characteristics of ground vibrations measured from a test blast. The reduction of the rock properties in EDZ could be predicted accurately with an overlapping effect due to sequential blasting. Numerical analyses using FLAC were made of several cases to determine the possible influence of the EDZ generated from different blasting designs and rock conditions.
Tunnel and Underground Space | 2016
Jae Hong Chung; Seung Hun Park; Seung Jun Lee; Seungwon Yu; Woo Hee Lee; Sangki Kwon
This paper presents experimental results to investigate the affects of acidic solution under loading condition on rock properties. In the experiment, the variations of various rock properties including effective porosity, thermal conductivity, and etc were investigated with different pHs of solution and magnitudes of loading. The results show that the rock property change was increased with low pH under loading. It was predicted that chemical reaction rate would be increased in low pH. Below the crack initiation stress of the rock specimen, the variation of rock property change was reduced with increased loading. It could be explained with the reduced chemical reaction area by the compressional loading if there is no crack generation.
Journal of Korean Society for Rock Mechanics | 2015
Sangki Kwon; Chang-Soo Lee; Seung-Hun Park
The evaluation of THM coupling behavior in deep underground repository condition is essential for the long term safety and stability assessment of high-level radioactive waste repository. In order to develop reliable THM analysis techniques effectively, an international cooperation project, DECOVALEX, is carried out. In DECOVALEX-2015 Task B2, the in situ THM experiment planned to be conducted by JAEA was modeled by the research teams from the participating countries. In this study, a THM coupling technique combining TOUGH2 and FLAC was developed and applied to 1 dimensional THM modeling, in which rock, buffer, and heater are considered. The results were compared with those from other research teams.