• Geomechanics and Engineering
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• 제24권5호
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• pp.491-503
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• 2021

Shallow tunnels are vulnerable to earthquakes, and shallow ground is usually inhomogeneous. Based on the limit equilibrium method and variational principle, a solution for the seismic collapse mechanism of shallow tunnel in inhomogeneous ground is presented. And the finite difference method is employed to compare with the analytical solution. It shows that the analytical results are conservative when the horizontal and vertical stresses equal the static earth pressure and zero at vault section, respectively. The safety factor of shallow tunnel changes greatly during an earthquake. Hence, the cyclic loading characteristics should be considered to evaluate tunnel stability. And the curve sliding surface agrees with the numerical simulation and previous studies. To save time and ensure accuracy, the curve sliding surface with 2 undetermined constants is a good choice to analyze shallow tunnel stability. Parameter analysis demonstrates that the horizontal semiaxis, acceleration, ground cohesion and homogeneity affect tunnel stability greatly, and the horizontal semiaxis, vertical semiaxis, tunnel depth and ground homogeneity have obvious influence on tunnel sliding surface. It concludes that the most applicable approaches to enhance tunnel stability are reducing the horizontal semiaxis, strengthening cohesion and setting the tunnel into good ground.

• Geomechanics and Engineering
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• 제32권6호
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• pp.639-652
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• 2023

Stepped earth slopes incorporated with anti-slide piles are widely utilized in landslide disaster preventions. Explicit consideration of the three-dimensional (3D) effect in the slope design warrants producing more realistic solutions. A 3D limit analysis of the stability of pile stabilized stepped slopes is performed in light of the kinematic limit analysis theorem. The influences of seismic excitation and surcharge load are both considered from a kinematic perspective. The upper bound solution to the factor of safety is optimized and compared with published solutions, demonstrating the capability and applicability of the proposed method. Comparative studies are performed with respect to the roles of 3D effect, pile location, pile spacing, seismic and surcharge loads in the safety assessments of stepped slopes. The results demonstrate that the stability of pile reinforced stepped slopes differ with that of single stage slopes dramatically. The optimum pile location lies in the upper portion of the slope around L_x/L = 0.9, but may also lies in the shoulder of the bench. The pile reinforcement reaches 10% universally for a looser pile spacing D_c/d_p = 5.0, and approaches 70% when the pile spacing reaches D_c/d_p = 2.0.

• 한국지반환경공학회 논문집
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• 제24권5호
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• pp.13-20
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• 2023

강릉지역은 유기질토가 생성되기 적합한 환경을 지닌 지역으로 유기질토 상부와 하부에 퇴적 모래층이 분포되어 있는 충적층 지반이 존재한다. 본 연구는 모래층 사이에 유기질토 및 점토가 협재된 지반 상부에 조성된 강릉지역을 통과하는 철도노반의 내진 안전성을 평가하기 위하여 상사율을 고려한 철도노반 및 지반 모형을 제작하여 진동대 시험을 실시하고 유효응력 해석 결과값을 비교하여 내진 안정성을 평가하였다. 적용된 지진파는 인공지진파, 경주지진파, Borah 지진파, Nahanni 지진파, Tabas 지진파를 적용하였으며 상부 모래층의 최대 응답가속도는 0.239g(인공지진파), 과잉간극수압비는 0.509(Borah파)가 발생하는 것으로 분석되었다. 신설노반의 하부지반에 적용된 jet grouting에 의한 지반보강 효과로 인해 신설 노반의 발생변위는 기존노반에 비해 최소 33.7%에서 최대 56.7% 감소한 것으로 나타났다. 진동대 시험결과는 Flac 프로그램의 Finn 모델을 적용한 유효응력해석으로 검증하였으며, 진동대 시험값과 유사한 경향을 나타내었다.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2009년도 춘계 학술발표회
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• pp.620-625
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• 2009

The seismic slope stability is most often evaluated by the pseudo-static limit analysis, in which the earthquake loading is simplified as static inertial loads acting in horizontal and/or vertical directions. The transient loading is represented by constant acceleration via the pseudostatic coefficients. The result of a pseudostatic analysis is governed by the selection of the value of the pseudostatic coefficient. However, selection of the value is very difficult and often done in an ad hoc manner without a sound physical reasoning. In addition, the maximum acceleration is commonly estimated from the design guideline, which cannot accurately estimate the dynamic response of a slope. There is a need to perform a 2D dynamic analysis to properly define the dynamic response characteristics. This paper develops the modified one-dimensional seismic site response analysis. The modified site response analysis adjusts the density of the layers to simulate the change in mass and weight of the layers of the slope with depth. Multiple analyses are performed at various locations within the slope to estimate the change in seismic response of the slope. The calculated peak acceleration profiles with depth from the developed procedure are compared to those by the two-dimensional analyses. Comparisons show that the two methods result in remarkable match.

• Geomechanics and Engineering
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• 제10권1호
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• pp.59-76
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• 2016

The non-linear Hoek-Brown failure criterion has been widely accepted and applied to evaluate the stability of rock slopes under plane-strain conditions. This paper presents a kinematic approach of limit analysis to assessing the static and seismic stability of three-dimensional (3D) rock slopes using the generalized Hoek-Brown failure criterion. A tangential technique is employed to obtain the equivalent Mohr-Coulomb strength parameters of rock material from the generalized Hoek-Brown criterion. The least upper bounds to the stability number are obtained in an optimization procedure and presented in the form of graphs and tables for a wide range of parameters. The calculated results demonstrate the influences of 3D geometrical constraint, non-linear strength parameters and seismic acceleration on the stability number and equivalent strength parameters. The presented upper-bound solutions can be used for preliminary assessment on the 3D rock slope stability in design and assessing other solutions from the developing methods in the stability analysis of 3D rock slopes.

• 한국지진공학회:학술대회논문집
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• 한국지진공학회 2001년도 추계 학술발표회 논문집 Proceedings of EESK Conference-Fall 2001
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• pp.139-146
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• 2001

The seismic safety analysis were performed for the center-core rockfill dam(CCRD) The static and pseudo-static FEM analysis using seismic coefficient Method, and dynamic FEM analysis using Hachinohe earthquake wave(0.12g) were used for the seismic safety of CCRD. The results of seismic analysis were that the factor of safety of down slope was 1.5, horizontal displacement is about 14.3cm, and vertical displacement is 3.3cm at dam creast. The model dam did not show any seismic stability problems for 0.12g. And much more research is still necessary in seismic safety of CCRD.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2003년도 추계학술대회논문집
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• pp.338-344
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• 2003

The seismic analysis method of spent fuel storage structures for PHWR plant is introduced in comparison with the method for PWR plant. Investigating the structural characteristics of the storage structures, the former is vertically stacked fuel storage trays, while the latter is welded honeycomb type structure. However, as both structures are submerged and free standing, the analysis methods to anticipate the seismic response of both structures are complicated. For the better estimation of actual seismic response, how to model the dynamic properties and the structural behaviour is the key issue. In this paper, the overall procedures of the seismic modelling and stability check for seismic sliding and overturning of the two different storage structures are discussed in the viewpoint of analysis reliability

• 농업과학연구
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• 제47권4호
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• pp.963-978
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• 2020

Earthquakes can induce a large number of landslides and cause very serious property damage and human casualties. There are two issues in study on earthquake-induced landslides: (1) slope stability analysis under seismic loading and (2) debris flow run-out analysis. This study aims to review technical studies related to the development and application of earthquake-induced landslide models (seismic slope stability analysis). Moreover, a pilot application of a physics-based slope stability model to Mt. Umyeon, in Seoul, with several earthquake scenarios was conducted to test regional scale seismic landslide mapping. The earthquake-induced landslide simulation model can be categorized into 1) Pseudo-static model, 2) Newmark's dynamic displacement model and 3) stress-strain model. The Pseudo-static model is preferred for producing seismic landslide hazard maps because it is impossible to verify the dynamic model-based simulation results due to lack of earthquake-induced landslide inventory in Korea. Earthquake scenario-based simulation results show that given dry conditions, unstable slopes begin to occur in parts of upper areas due to the 50-year earthquake magnitude; most of the study area becomes unstable when the earthquake frequency is 200 years. On the other hand, when the soil is in a wet state due to heavy rainfall, many areas are unstable even if no earthquake occurs, and when rainfall and 50-year earthquakes occur simultaneously, most areas appear unstable, as in simulation results based on 100-year earthquakes in dry condition.

• 한국산업융합학회 논문집
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• 제23권6_1호
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• pp.881-888
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• 2020

A butterfly valve is a valve that adjusts flow rate by rotating a disc for about 90° with respect to the axis that is perpendicular to the flow path from the center of its body. This valve can be manufactured for low-temperature, high-temperature and high-pressure conditions because there are few restrictions on the used materials. However, the development of valves that can be used in a 600℃ environment is subject to many constraints. In this study, the butterfly valve's stability was evaluated by a fluid-structured interaction analysis, thermal-structure interaction analysis, and seismic analysis for the development of valves that can be used in high-temperature environments. When the reverse-pressure was applied to the valve in the structural analysis, the stress was low in the body and seat compared to the normal pressure. Compared with the allowable strength of the material for the parts of the valve system, the minimum safety factor was approximately 1.4, so the valve was stable. As a result of applying the design pressures of 0.5 MPa and 600℃ under the load conditions in the thermal-structural analysis, the safety factor in the valve body was about 3.4 when the normal pressure was applied and about 2.7 when the reverse pressure was applied. The stability of the fluid-structure interaction analysis was determined to be stable compared to the 600℃ yield strength of the material, and about 2.2 for the 40° open-angle disc for the valve body. In seismic analysis, the maximum value of the valve's stress value was about 9% to 11% when the seismic load was applied compared to the general structural analysis. Based on the results of this study, the structural stability and design feasibility of high-temperature valves that can be used in cogeneration plants and other power plants are presented.

• 한국지역지리학회지
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• 제18권4호
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• pp.351-363
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• 2012

한반도는 주변의 북중국, 일본과 같이 지구조적 활동이 활발한 지역들에 비해 상대적으로 안정된 것으로 알려져 있다. 그럼에도 불구하고 한반도 남동부 지역을 중심으로 지속적으로 보고되고 있는 제4기 단층의 존재는 한반도의 신기 지체구조 운동의 성격을 본질적이고 구체적으로 이해할 필요가 있음을 시사한다. 경주시 양남면 일대에서 확인된 수렴단층과 읍천단층은 그 최종 운동 시기가 제4기 후기로 확인되고 있어 현생 지구조 체계 하에서 발생하고 있는 지각 변형 사건임을 분명히 지시해 주고 있다. 이들 단층운동과 관련된 동-서 방향의 최대 압축 응력은 인도-호주판과 유라시아 판의 충돌 응력이 원거리에 전파되는 과정에서 발생하는 것으로 이해된다. 특징적으로 한반도 남동부 지역의 제4기 단층들은 반복적 재활성 가능성이 크므로 잠재적 지진 재해에 대비해야 할 것으로 판단되며, 특히 본 연구는 연구 지역 내에 위치하고 있는 원자력 발전소 인근의 지진 안정성에 관한 중요한 단서를 제공하고 있다.