• Geomechanics and Engineering
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• 제15권6호
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• pp.1193-1205
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• 2018

A footing located on slopes possess relatively lower bearing capacity as compared to the footing located on the level ground. The bearing capacity further reduces under seismic loading. The adverse effect of slope inclination and seismic loading on bearing capacity can be minimized by proving sufficient setback distance. Though few earlier studies considered setback distance in their analysis, the range of considered setback distance was very narrow. No study has explored the critical setback distance. An attempt has been made in the present study to comprehensively investigate the effect of setback distance on footing under seismic loading conditions. The pseudo-static method has been incorporated to study the influence of seismic loading. The rate of decrease in seismic bearing capacity with slope inclination become more evident with the increase in embedment depth of footing and angle of shearing resistance of soil. The increase in bearing capacity with setback distance relative to level ground reduces with slope inclination, soil density, embedment depth of footing and seismic acceleration. The critical value of setback distance is found to increase with slope inclination, embedment depth of footing and density of soil. The critical setback distance in seismic case is found to be more than those observed in the static case. The failure mechanisms of footing under seismic loading is presented in detail. The statistical analysis was also performed to develop three equations to predict the critical setback distance, seismic bearing capacity factor ($N_{{\gamma}qs}$) and change in seismic bearing capacity (BCR) with slope geometry, footing depth and seismic loading.

• 한국터널지하공간학회 논문집
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• 제25권3호
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• pp.187-200
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• 2023

본 연구에서는 주변 환경에 따른 굴착식 터널의 지진취약도 변화에 대한 분석을 진행하고 대표 지진취약도 모델을 제시하였다. 기 개발된 굴착식 터널의 지진취약도 모델들에 대한 분석을 진행한 후 각 모델들에 가중치를 부여하여 주변 환경에 맞게 새로 가중조합한 모델을 개발하였다. 주변 환경은 굴착식 터널 주변의 지반조건과 매설 깊이를 고려하였다. 지진취약도 곡선의 피해 발생 확률은 최대지반가속도(PGA)를 매개변수로 하여 결정된다. PGA가 0.3 g일 때 매설 깊이가 50 m이하의 조건에서는 경미한 손상을 초과하는 피해 확률이 20%, 매설 깊이가 50 m 이상 100 m 이하의 조건에서는 피해 확률이 10%, 매설 깊이 100 m 이상의 조건에서는 피해 확률이 3% 이하로 매설 깊이에 따라 피해 확률이 점차 낮아지는 것을 확인하였다. 또한 주변 지반이 토양으로 되어있을 때보다 암반으로 되어있을 때 동일한 지표의 PGA에 대해 같은 매설 깊이에서 피해 확률이 크게 나타나며, 매설 깊이가 깊어질수록 피해 확률이 작아진다. 이 연구는 향후 터널의 종합적 지진취약도 함수 개발에 유용하게 사용될 것으로 기대된다.

• 한국지진공학회:학술대회논문집
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• 한국지진공학회 2000년도 춘계 학술발표회 논문집 Proceedings of EESK Conference-Spring
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• pp.194-201
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• 2000

In this study the modified seismic coefficient method for seismic analysis of buried box structures is developed for practical purpose. The loading coefficient in the modified seismic coefficient method is determined from the results of the response displacement analysis. In the developed method adequate velocity response spectrum in accordance with soil condition is also needed to seismic design of buried box structures, In order to investigate applicability of the modified seismic coefficient method various analyses are performed with different parameters such as depth of base rock height and width of box buried depth and value of standard penetration test. Results from the modified seismic coefficient method are compared with those of the response displacement method in terms of the maximum bending moment and the location of it. From the comparison it is shown that the feasibility of the modified seismic coefficient method for seismic analysis of buried box structures.

• Geomechanics and Engineering
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• 제23권1호
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• pp.71-83
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• 2020

Cantilever sheet pile walls are subjected to surcharge loading located on the backfill soil and at different distances from the top of the wall. The response of cantilever sheet pile walls to surcharge loadings at varying distances under seismic conditions is scarce in literature. In the present study, the influence of uniform surcharge load on cantilever sheet pile wall at varying distances from the top of the wall under seismic conditions are analyzed using finite difference based computer program. The results of the numerical analysis are presented in non-dimensional form like variation of bending moment and horizontal earth pressure along the depth of the sheet pile walls. The numerical analysis has been conducted at different magnitudes of horizontal seismic acceleration coefficient and vertical seismic acceleration coefficients by varying the magnitude and position of uniform surcharge from the top of the wall for different embedded depths and types of soil. The parametric study is conducted with different embedded depth of sheet pile walls, magnitude of surcharge on the top of the wall and at a distance from the top of the wall for different angles of internal friction. It is observed that the maximum bending moment increases and more mobilization of earth pressure takes place with increase in horizontal seismic acceleration coefficients, magnitude of uniform surcharge, embedded depth and decrease in the distance of surcharge from the top of the wall in loose sand.

• Structural Engineering and Mechanics
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• 제70권5호
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• pp.563-570
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• 2019

To analyze the seismic reliability of concrete rectangular liquid storage structures (CRLSSs), assuming that the wall thickness and internal liquid depth of CRLSSs are random variables, calculation models of CRLSSs are established by using the Monte Carlo finite element method (FEM). The principal stresses of the over-ground and buried CRLSSs are calculated under three rare fortification intensities, and the failure probabilities of CRLSSs are obtained. The results show that the seismic reliability increases with the increase of wall thickness, whereas it decreases with the increase of liquid depth. Between the two random factors, the seismic reliability of CRLSSs is more sensitive to the change in wall thickness. Compared with the over-ground CRLSS, the buried CRLSS has better reliability.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2006년도 춘계 학술발표회 논문집
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• pp.562-571
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• 2006

Mean shear wave velocity of the upper 30m $(V_s30)$ used as the current site classification criterion for determining seismic design ground motions in Korea was established based on the typical depth of site investigations in western US, in which the depth to bedrock is much deeper than that in Korea. In this study, to establish appropriate site classification system for site conditions of Korea, site investigations including in-situ seismic tests to determine shear wave velocity $(V_s)$ were carried out at total 72 sites in Korean peninsula. The mean $V_s's$ to the depths of 5m, 10m, 15m, 20m and 25m together with the $V_s30$ at the testing sites were determined, and the correlation between the mean $V_s$ to a depth shallower than 30m and the $V_s30$ was drawn and suggested for the efficient seismic site classification in Korea. The proposed correlation could be utilized for the seismic design in case of the $V_s$ profiles shallower than 30 m in depth. The correlation in this study, nevertheless, requires further modification by means of the accumulation of various site data in Korea.

• 지구물리와물리탐사
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• 제22권4호
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• pp.225-238
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• 2019

최적의 심도 영역 속도를 도출하기 위한 구조보정 속도분석(MVA, migration velocity analysis) 기법을 해양에서 취득한 원거리 다중채널 탄성파 자료에 적용하여 그 효용성을 확인한다. 지금까지 통상적으로 수행된 시간 영역 자료처리 결과는 지질학적 층서해석에는 무리 없는 결과이나, 어느 정도 가능성이 있는 플레이나 리드 지역에서의 유가스 탐사에서는 저류층 지질모델 구축, 시추 설계, 매장량 계산에서 반드시 심도 영역 속도 구조와 영상이 필요하다. 데이터 영역에서 근사 방식을 사용한 공통 중간점 기반 속도 분석으로부터 도출한 속도는 처음부터 오차를 내재하여 불확실성이 높다. 반면에, 이를 보완해 줄 검층 자료가 없는 상황에서 실측 규모의 속도 구조를 도출하는데 있어 이미지 영역 구조보정 속도분석 기법은 상당히 효율적인 방법이다. 이 연구에서는 해양에서 취득한 다중 채널 탄성파자료에 대해 합리적인 결과를 도출하기 위해 시간 영역에서 신호의 품질을 최적화하고, 이 자료에 대하여 반복적으로 MVA 기법을 적용함으로써 심도영역 속도 및 구조보정 단면도를 도출하였다. 시간 영역 속도를 단순히 Dix 방정식에 의해 심도영역으로 변환한 속도를 이용하여 생성한 결과(공통 수신점 모음도 및 중합 단면도)와 MVA 기법을 이용한 심도영역 자료처리를 통해 도출된 속도를 이용하여 생성한 결과를 비교함으로써, 심도영역 결과가 보다 합리적임을 확인하였다. 심도 영역으로 도출된 속도는 중합전 심도 구조보정에 바로 사용될 수 있을 뿐만 아니라, 현장 자료의 파형역산 적용 시 초기 모델로 활용함으로써 역산 수행 과정에서 발생할 수 있는 국부 최소(local minima) 문제를 최소화할 수 있다.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2007년도 추계학술대회 논문집
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• pp.564-568
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• 2007

Gas hydrate has been attractive topic for two dedicates because it may cause the global warming, ocean hazards associated with the instability of marine slope due to the gas hydrate release as well as high potential of future energy resources. The study on gas hydrate in Ulleung basin has been performed since 1999 to explore the potential and distribution of gas hydrate offshore Korea. The numerous multi channel seismic data have been acquired and processed by Korea Institute of Geosciences and Mineral Resources (KIGAM). The results showed clearly the gas hydrate indicators such as pull up structure, bottom simulating reflector (BSR), seismic blanking zone. The prestack depth migration has been considered as fast and accurate technique to image the subsurface. In this paper, we will present both the conventional seismic data processing and apply Kirchhoff prestack depth migration for gas hydrate data set. The results will be applied for core sample collections and for proposal more detail 2D with long offset or 3D seismic exploration.

• Earthquakes and Structures
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• 제26권3호
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• pp.229-237
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• 2024

This paper studied the subgrade spring stiffness and its influencing factors in the seismic deformation method of circular tunnel. Numerical calculations are performed for 3 influencing factors: stratum stiffness, tunnel diameter and burial depth. The results show that the stratum stiffness and tunnel diameter have great influence on the subgrade spring stiffness. The subgrade spring stiffness increases linearly with stratum stiffness increasement, and decreases with the tunnel diameter increasement. When the burial depth ratio (burial depth/tunnel diameter) exceeds to 5, the subgrade spring stiffness has little sensitivity to the burial depth. Then, a proposed formula of subgrade spring stiffness for the seismic deformation method of circular tunnel is proposed. Meanwhile, the internal force results of the seismic deformation method are larger than that of the dynamic time history method, but the internal force distributions of the two methods are consistent, that is, the structure exhibits elliptical deformation with the largest internal force at the conjugate 45° position of the circular tunnel. Therefore, the seismic deformation method based on the proposed formula can effectively reflect the deformation and internal force characteristics of the tunnel and has good applicability in engineering practice.

• 한국마린엔지니어링학회:학술대회논문집
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• 한국마린엔지니어링학회 2006년도 전기학술대회논문집
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• pp.209-210
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• 2006

Digital technology has been applied to marine seismic survey to develop data processing technology and multi-channel marine seismic survey. In result, high-resolution marine seismic survey ended in a success. Surveys are conducted for various purposes using various frequencies of acoustic sources. A low frequency source is used for deeper penetration and a high frequency source is used for higher resolution survey. In this study, a multi-source system was used for multi-channel marine seismic survey to acquire seismic sections of both low and high frequencies. Variations of depth of penetration and resolution would be used to achieve more accurate analysis of formations. In this study, the multi-source system consists of Bubble Pulser(400 Hz) for low frequency source and Sparker(1.5 kHz) for high frequency source.