• Proceedings of the Korea Water Resources Association Conference
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• 2018.05a
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• pp.19-19
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• 2018

최근 경주, 울산, 포항 등 경상도 지역에서 잇달아 발생한 대규모 지진으로 인해 사회기반시설물의 내진 안전성이 이슈가 되고 있다. 지진 안전 국가라고 여겨지던 우리나라는 상대적으로 지진에 대한 대비가 매우 부족한 실정이며, 자칫 대규모 피해로 이어질 우려가 있다. 특히 상수관망의 경우, 지중에 매설되어 있는 특성상 지진에 취약하고, 그 피해를 발견하기 어려워 장기적인 피해가 불가피하다. 상수관로의 지진피해는 누수와 파손으로 구분할 수 있으며, 파손관의 경우 용수공급능력을 크게 저하시키기 때문에 신속한 복구가 요구된다. 파손관의 복구는 부근에 위치한 차단밸브를 닫아 피해관로의 통수를 차단한 후에 복구 작업을 진행하는 것이 일반적이다. 이때, 차단밸브의 위치에 따라 단수구역이 광범위하게 발생할 수 있어 시스템 전반의 용수공급능력 저하로 이어질 가능성이 있다. 본 연구에서는 지진 발생 후 피해관로의 효율적인 복구전략 마련을 위한 상수관망 지진피해 복구 시뮬레이션 모형을 개발하였다. 개발 모형은 피해복구에 따른 상수관망 시스템의 용수공급능력을 정량적으로 산정할 수 있으며, 지진 발생과 같은 비정상 상황의 시스템 용수공급능력을 수리학적으로 정확하게 해석하기 위해 압력기반의 해석(Pressure-driven analysis, PDA)을 적용하였다. 또한, 피해관로의 복구 시, 차단밸브에 의해 발생되는 단수구역을 탐색한 후, 수리해석 모의에 적용함으로써 현실적인 용수공급 상황을 모의할 수 있도록 하였다. 본 연구에서는 개발모형을 활용하여 차단밸브의 위치 및 개수가 단수구역의 범위 및 지진복구에 미치는 영향을 정량적으로 비교 분석하였으며, 이를 통해 효율적인 지진피해 복구 전략을 제시하였다.

• Economic and Environmental Geology
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• v.51 no.2
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• pp.149-166
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• 2018

Many large earthquakes have continuously been reported and resulted in significant human casualties and extensive damages to properties globally. The accident of Fukushima nuclear power plant in Japan was caused by a mega-tsunami, which is a secondary effect associated with the Tohoku large earthquake (M=9.0, 2011. 3. 11.). Most earthquakes occur by reactivation of pre-existing active faults. Therefore, the importance of paleoseismological study have greatly been increased. The Korean peninsula has generally been considered to be a tectonically stable region compared with neighboring countries such as Japan and Taiwan, because it is located on the margin of the Eurasian intra-continental region. However, the recent earthquakes in Gyeongju and Pohang have brought considerable insecurity on earthquake hazard. In particular, this region should be secure against earthquake, because many nuclear facilties and large industrial facilities are located in this area. However, some large earthquakes have been reported in historic documents and also several active faults have been reported in southeast Korea. This study explains the evaluation methods of geological structures on active fault, fault damage zone, the relationship between earthquake and active fault, and respect distance. This study can contribute to selection of safe locations for nuclear facilities and to earthquake hazards and disaster prevention.

• Asia-pacific Journal of Multimedia Services Convergent with Art, Humanities, and Sociology
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• v.8 no.3
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• pp.467-475
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• 2018

Recently earthquakes have been increasing worldwide, and the largest earthquake of 5.8 on the Richter scale occurred on September 12, 2016 in the Gyeongju area. After the earthquake, more than 200 aftershocks have occurred from January 2017 to December 2017. The largest earthquake in 2017 was a 4.3-magnitude earthquake near Pohang on November 15. In this study, we tried to analyze the coordinate change due to the earthquake using the data of the CORS(Continuously Operating Reference Station) in Korea. In order to analyze the change of coordinates due to the earthquake in Pohang area on November 15, 2017, data processing was performed by kinematic method. And from January 2017 to December 2017, observation data of 9 stations in Korea were analyzed by relative positioning method and the change of coordinates due to earthquake was analyzed. As a result of the study, it was possible to estimate the instantaneous coordinate change due to the earthquake through the kinematic positioning, and it was suggested that there is no change in the coordinates of the domestic CORS by the relative positioning results. After the 2017 Gyeongju earthquake, aftershocks continue to occur, and it is necessary to monitor the area continuously.

• Journal of the Earthquake Engineering Society of Korea
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• v.23 no.1
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• pp.9-18
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• 2019

In 2017 Pohang Earthquake, a number of residential buildings with pilotis at their first level were severely damaged. In this study, the results of an analytical investigation on the seismic performance and structural damage of two bearing wall buildings with pilotis are presented. The vibration mode and lateral force-resisting mechanism of the buildings with vertical and plan irregularity were investigated through elastic analysis. Then, based on the investigations, methods of nonlinear modeling for walls and columns at the piloti level were proposed. By performing nonlinear static and dynamic analyses, structural damages of the walls and columns at the piloti level under 2017 Pohang Earthquake were predicted. The results show that the area and arrangement of walls in the piloti level significantly affected the seismic safety of the buildings. Initially, the lateral resistance of the piloti story was dominated mainly by the walls resisting in-plane shear. After shear cracking and yielding of the walls, the columns showing double-curvature flexural behavior contributed significantly to the residual strength and ductility.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.34 no.3
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• pp.121-128
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• 2021

Piloti-type buildings in Korea are usually composed of lower frames and upper shear wall structures. Piloti-type buildings have been seriously damaged during earthquakes because of the construction of soft and weak stories. Piloti-type buildings with edge cores are two-way unsymmetric planes. This paper analyzed and obtained the dynamic response for structures modeled using a multistory two-way asymmetric system. The numerical results, obtained using the Newmark-β method, show the time-history responses and trends of maximum displacements and shear forces. The purpose of this study is to evaluate the effect of reinforcement on dynamic response when a shear wall or brace is reinforced in the corner opposite the piloti.

• Proceedings of the Korea Water Resources Association Conference
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• 2019.05a
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• pp.298-298
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• 2019

과거에 경험하지 못한 집중호우가 빈번하게 발생하고 규모가 큰 태풍의 내습이 발생하고 있다. 2018년 7월23일 발생한 라오스 댐붕괴 발생으로 인해 6,600명의 이재민이 발생하였으며, 2008년 중국 쓰촨성 지진에 의해 댐 수백개가 균열이 발생하는 위험한 상황에 이르는 등 댐 붕괴에 따른 대규모 재난의 위험상황은 항시 존재하고 있다. 는 상황에서 댐의 붕괴에 대한 많은 연구가 진행되었다. 이러한 댐 붕괴 상황에 대한 대비책으로 저수지 댐의 안전관리 및 재해예방에 관한 법률 제3조와 자연재해 대책법 제37조에 총저수용량 30만톤 이상의 저수지에 대해 비상대처계획 수립을 하도록 되어 있다. 최근 경주와 포항에서 발생한 규모 5.4이상의 지진이 발생하여 지진에 의한 재난의 위험이 가중되고 있는 상황에서 지진에 의한 댐붕괴에 대한 적절한 시나리오와 분석이 필요하다. 지금까지의 지진붕괴에 의한 EAP의 작성은 단순히 만수위 상태에서 댐의 붕괴시간이 급격히 붕괴되어 범람되는 분석을 하였다. 그러나 지진에 의한 댐의 붕괴에 이르는 지진의 규모는 댐 주변의 건축물, 교량, 심지어 대피소도 붕괴 및 범람에 안전할 수 없는 상황에 이르게 될 것이다. 그러나 현재의 EAP는 단순 범람만을 통해 위험도를 나타내는 것으로 작성되어 있어 이에 대한 수정이 필요하다. 본 연구에서는 지진에 의한 댐 붕괴 EAP 작성시 고려되어야 할 건물의 노후도, 교량, 공공시설물 등이 붕괴될 위험을 판단하고 이에 따른 범람도면의 작성과 시나리오가 작성되어야 한다. 이를 위한 행정안전부에서 제시된 지진 시 댐 붕괴 조건에서 고려되어야 할 시나리오의 구성요소에 대해 검토하였다.

• Journal of the Korean Geosynthetics Society
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• v.18 no.4
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• pp.107-114
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• 2019

In this paper, the P-wave multiple detection system for the fast and accurate earthquake early warning nearby the epicenter was developed. The developed systems were installed in five selected public buildings for the validation. During the monitoring, a magnitude 2.3 earthquake occurred in Pohang on 26 September 2019. P-wave initial detection algorithms were operated in three out of four systems installed in Pohang area and recorded as seismic events. At the nearest station, 5.5 km from the epicenter, P-wave signal was detected 1.2 seconds after the earthquake, and S-wave was reached 1.02 seconds after the P-wave reached, providing some alarm time. The maximum accelerations recorded in three different stations were 6.28 gal, 6.1 gal, and 5.3 gal, respectively. The alarm algorithm did not work, due to the high threshold of the maximum ground acceleration (25.1 gal) to operate it. If continuous monitoring and analysis are to be carried out in the future, the developed system could use a highly effective earthquake warning system suitable for the domestic situation.

• Journal of the Korean Geotechnical Society
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• v.34 no.5
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• pp.19-35
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• 2018

The necessity of predicting the spatial information of the site-specific seismic response, which is essential information for the comprehensive earthquake disaster countermeasures, is increasing for the mid-west urban areas where the earthquake-induced damages can be increased due to frequent occurrence of mid-scale earthquake such as 2016 Gyeongju Earthquake and 2017 Pohang Earthquake. Especially, researches on strategic securing of site survey datasets and understanding the site-specific site response characteristics were conducted for Gyeonggi-do, South Korea. In this study, a GIS-based framework for site-specific assessment of site response and induced vulnerable area in Gyeonggi-do, South Korea was proposed. Geo-Data based on GIS platform was constructed for regional estimation of geotechnical characteristics by collecting borehole and land coverage datasets. And the geo-spatial grid information was developed for deriving spatial distribution of geotechnical layer and site response parameters based on the optimization of the geostatistical interpolation method. Accordingly, base information for Improving earthquake preparedness measures was derived as seismic zonation map with administrative sub-units considering the quantitative site effect of Gyeonggi-do.

• Geophysics and Geophysical Exploration
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• v.22 no.3
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• pp.107-115
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• 2019

Recently, since earthquakes have happened frequently in Gyeongju and Pohang areas in Korea, the earthquake detection research gets lots of attention. Geophysical monitoring data have been changed during the earthquake activity because the huge amount of energy is accumulated. The change of telluric current can be predicted by both of piezoelectric and electrokinetic effects before or during the earthquake occurrence, and if the change value exceeds the conventional telluric current noise, we can measure changes in the electric field associated with earthquakes. In this study, we have self-developed and verified the system that can monitor the telluric current. In order to verify our telluric current monitoring system, we installed lines of 40 m (E-W direction) and 28 m (N-S direction) on the site in Pohang. The telluric currents were sampled at 1 kHz for about a month. We have compared and analyzed the data of earthquake signals and electrical noises based on the earthquakes that occurred during the monitoring period. We have monitored if there were significant signals related to the earthquake on measured time series data. Through this study, we will suggest the direction of continuous research in the future.

• Journal of the Korean Geotechnical Society
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• v.35 no.7
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• pp.15-27
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• 2019

The purpose of this study is to investigate the mechanism about damages occurring at quay wall and backfill in Youngilman Port during Pohang earthquake (M5.4) on November 15, 2017. In the field investigation, the horizontal displacement of the caisson occurred between 5 cm and 15 cm, and the settlement at backfill occurred higher than 10 cm. 2D-effective Stress Analysis was performed to clarify the mechanism for the damage. The input earthquake motion used acceleration ($3.25m/s^2$) measured at bedrock of Pohang habor. Based on a numerical analysis, it was found that the effective stress decreased due to the increase of excess pore pressure in the backfill ground and the horizontal displacement of the caisson occurred by about 14 cm, and the settlement occurred by about 3 cm. In backfill, the settlements occurred between 6 cm and 9 cm. This is similar to field investigation results. Also, it was found that the backfill soil was close to the Mohr-Coulomb failure line due to the cyclic loading from the effective stress path and the stress-strain behavior. It may be related to decreasing of bearing capacity induced by the reduction of effective stress caused by the increase of the excess pore water pressure.