• Title/Summary/Keyword: Liquefaction evaluation

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A Study on transverse Behavior of Lifeline System Due to Liquefaction-induced Permanent Ground Displacement (액상화 영구지반변형에 의한 라이프라인 구조물의 횡방향 거동에 관한 연구)

  • 김문겸
    • Proceedings of the Earthquake Engineering Society of Korea Conference
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    • 1998.10a
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    • pp.369-376
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    • 1998
  • The purpose of the present study is to analyze the response of pipelines subjected to liquefaction-induced permanent ground displacement and to discuss the failure prediction of domestic waterway pipelines. Initially here, characteristics of liquefaction are reviewed and then permanent ground displacement is investigated base on previous earthquake hazard cases. Next, considering the distribution of the transverse permanent ground displacement and equivalent spring constant effect, formulas obtained by a beam theory are established to analyze continuous pipelines. This analysis was performed without consideration of axial effects. So the finite element analysis was used in order to consider the axial stiffness of soil. As a result, degree of liquefaction, width of deformed ground and axial stiffness are crucial points for evaluation the failure of pipelines subjected to permanent ground displacement.

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Characteristics of Liquefaction Behavior with Earthquake Load Frequency (지진하중 주파수에 따른 액상화 거동 특성)

  • Yoon, Won-Sub
    • Journal of the Korean Society of Industry Convergence
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    • v.22 no.6
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    • pp.739-748
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    • 2019
  • In this study, cyclic triaxial tests were performed for liquefaction characteristics according to earthquake loading frequency. The test period was tested for 0.1Hz, 0.2Hz, 0.5Hz 1.0Hz, 1.5Hz. It was analyzed that the number of earthquake loading increases as the test result frequendy increases. Therefore, additional study of the liquefaction evaluation method was needed considering the local characteristics of the high frequency earthquakes in Korea and the cyclic triaxial test frequency(0.1Hz), which is mainly used in the design.

Evaluation of the Numerical Liquefaction Model Behavior with Drainage Condition (배수조건에 따른 액상화 수치모델의 거동평가)

  • Lee, Jin-Sun;Kim, Seong-Nam;Kim, Dong-Soo
    • Journal of the Korean Geotechnical Society
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    • v.35 no.11
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    • pp.63-74
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    • 2019
  • Numerical liquefaction model and response history analysis procedure are verified based on dynamic centrifuge test results. The test was a part of the Liquefaction Experiments Analysis Project (LEAP). The model ground was formed inside of rigid box by using the submerged Ottawa F65 sand with a relative density of 55% and 5° of surface inclination. A tapered sinusoidal wave with a frequency of 1 Hz was applied to the base of the model box. Numerical analyses were performed by two dimensional finite difference method in prototype scale. The soil is modeled to show hysteretic behavior before shear failure, and Mohr-Coulomb model is applied for shear failure criterion. Byrne's liquefaction model was applied to track the changes in pore pressure due to cyclic loading after static equilibrium. In order to find an appropriate flow condition for the liquefaction analysis, numerical analyses were performed both in drained and undrained condition. The numerical analyses performed under the undrained condition showed good agreement with the centrifuge test results.

Soil Depth Information DB Construction Methods for Liquefaction Assessment (액상화 평가를 위한 지층심도DB 구축 방안)

  • Gang, ByeongJu;Hwang, Bumsik;Kim, Hansam;Cho, Wanjei
    • Journal of the Korean GEO-environmental Society
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    • v.20 no.3
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    • pp.39-46
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    • 2019
  • The liquefaction is a phenomenon that the effective stress becomes zero due to the rapidly accumulated excess pore water pressure when a strong load acts on the ground for a short period of time, such as an earthquake or pile driving, resulting in the loss of the shear strength of the ground. Since the Geongju and Pohang earthquake, liquefaction brought increasing domestic attention. This liquefaction can be assessed mainly through the semi-empirical procedures proposed by Seed and Idriss (1982) and the liquefaction risk based on the penetration resistance obtained from borehole DB and SPT. However, the geotechnical information data obtained by the in-situ tests or boring information fundamentally have an issue of the representative of the target area. Therefore, this study sought to construct a ground information database by classifying and reviewing the ground information required for liquefaction assessment, and tried to solve the representative problem of the soil layer that is subject to liquefaction evaluation by performing spatial interpolation using GIS.

Compilation of liquefaction and pyrolysis method used for bio-oil production from various biomass: A review

  • Ahmad, Syahirah Faraheen Kabir;Ali, Umi Fazara Md;Isa, Khairuddin Md
    • Environmental Engineering Research
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    • v.25 no.1
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    • pp.18-28
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    • 2020
  • In this paper the authors provide comparative evaluation of current research that used liquefaction and pyrolysis method for bio-oil production from various types of biomass. This paper review the resources of biomass, composition of biomass, properties of bio-oil from various biomass and also the utilizations of bio-oil in industry. The primary objective of this review article is to gather all recent data about production of bio-oil by using liquefaction and pyrolysis method and their yield and properties from different types of biomass from previous research. Shortage of fossil fuels as well as environmental concern has encouraged governments to focus on renewable energy resources. Biomass is regarded as an alternative to replace fossil fuels. There are several thermo-chemical conversion processes used to transform biomass into useful products, however in this review article the focus has been made on liquefaction and pyrolysis method because the liquid obtained which is known as bio-oil is the main interest in this review article. Bio-oil contains hundreds of chemical compound mainly phenol groups which make it suitable to be used as a replacement for fossil fuels.

Evaluation of Subsurface Liquefaction through Spectrum Intensity at Surface (지표면 스펙트럼 강도를 통한 지반의 액상화 평가에 대한 연구)

  • ;Towhata, Ikou
    • Geotechnical Engineering
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    • v.14 no.2
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    • pp.9-20
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    • 1998
  • The earthquake-induced liquefaction of ground brings high possibility of failure of lifeline. If subsurface liquefaction is detected immediately after an earthquake the damage caused by the failure of lifeline can be reduced. The goal is achieved by deploying many accelerometers in the area of possible liquefaction and collecting records through a wireless network. This paper attempts to develop a measure to interpret the collected data oft surface motion and to assess the thickness of liquefied layers. For this purpose. both analysis of earthquake records and shaking table tests on model ground were carried out. It was shown that the thickness of liquefied layers can be assessed by using the maximum acceleration and the spectrum intensity at the surface.

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Development of energy-based excess pore pressure generation model using damage potential (손상잠재력을 이용한 에너지-과잉간극수압 발현 모델 개발)

  • Park, Keun-Bo;Kim, Soo-Il;Kim, Ki-Poong;Lee, Chae-Jin
    • Proceedings of the Korean Geotechical Society Conference
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    • 2008.03a
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    • pp.575-586
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    • 2008
  • The main objective of this paper is to develop an improved model for the analysis of liquefaction potential and to predict excess pore pressure (EPP) using the proposed model that can simulate behavior of saturated sand under earthquake loading conditions. The damage concept is adopted for the development of the proposed model. For the development of the model, a general formulation based on experimental results and damage potential using cumulative absolute velocity (CAV) is proposed for a more realistic description of dynamic responses of saturated sand. Undrained dynamic triaxial tests are conducted using earthquake loading conditions. Based on test results, the NCER-NCW function in terms of $w_d$ and CAV is developed. Procedure for the evaluation of EPP and determination of model parameters for the proposed model is presented as well. For the determination of initial liquefaction, the minimum curvature method using the NCS-NCW curve is proposed. It is observed that predicted initial liquefaction using the proposed method agrees well with measured initial liquefaction. From results of additional undrained dynamic triaxial tests, it is seen that predicted EPP generation using the proposed model agrees well with measured results for earthquake loading cases.

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Effect of Re-liquefaction System on Operating Expenditure of LNGC in Terms of Fuel Oil Consumption Cost and BOG Combustion Cost (천연가스 운반선의 재액화 장치가 운항비용에 미치는 영향에 관한 연구: 연료비용 및 증발 가스 연소비용 관점에서)

  • You, Youngjun;Lee, Joon Chae
    • Journal of the Society of Naval Architects of Korea
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    • v.57 no.3
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    • pp.152-159
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    • 2020
  • Ship owners had pursued higher benefits by demanding the new design and construction of ships with higher operational efficiency. There was a necessity for shipyards to suggest a more economical design and advanced operation concept in order to meet the demands. Especially, since BOG combustion and activation of the re-liquefaction unit had to be taken into account in ship design in addition to fuel oil and gas consumption, the evaluation of the operating efficiency considering the technological trends was necessary. In this paper, it was aimed to study the design philosophy and operation strategy by considering the effect of fuel oil and gas consumption, BOG combustion, and activation of the re-liquefaction unit on the operating cost for laden voyage according to ship speed, BOR, and activation of the re-liquefaction unit. For this purpose, the costs were acquired by conducting the sailing simulation of an LNGC based on a mathematical model including the maneuvering equations of motion. The design philosophy and operation strategy was reviewed in terms of the operating cost.

Evaluation on the Seismic Performance of Port Structures using GIS (GIS를 이용한 항만구조물의 내진성능 평가기법)

  • Kim, Na Young;Kang, In Joon;Choi, Hyun;Kim, Tae Hyo
    • Journal of Korean Society for Geospatial Information Science
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    • v.22 no.4
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    • pp.31-38
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    • 2014
  • Seismic of the Korean Peninsula is terrible about 1,900 times. Lately, because of a world-occurring seismic, investment of seismic design about ground & structures come to the force as means to protect national life and property. This study evaluated having seismic performance above design criteria among the existing port structures not applied seismic design. Based on the results, classified apprehensive area of liquefaction from seismic performance evaluation and made hazards according to liquefaction risk & structural performance using the analysis of seismic performance and GIS method. After Establishing quantitative & detailed input database through liquefaction evaluation and seismic performance, analysed all seismic data are used directly valuation data on repair reinforcement for apprehensive area of earthquakes.

The Study on Liquefaction Characteristics of Silty Sand Soils by Cyclic Triaxial Test (반복삼축시험에 의한 실트 모래 지반의 액상화 특성 연구)

  • Lee, Song;Jeon, Je-Sung;Kim, Tae-Hwun
    • Journal of the Korean Geotechnical Society
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    • v.15 no.4
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    • pp.133-152
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    • 1999
  • The cyclic triaxial test was carried out to research liquefaction characteristics and sample disturbance effects of silty sand soils at the west coast in Korea. First, liquefaction in silty sand was generated when axial strain approached to $\pm10%$ of strain and behavior of pore pressure was similar to the formula suggested by Seed, Martin, and Lysmer(1975). Also, it was found that dilatancy was generated at failure. Secondly, the liquefaction evaluation methods suggested by many researchers were carried out and the results were compared. In these methods the weak depth in liquefaction was similar and the method carried out by cyclic triaxial test on remolded sample showed the least safety factor. Thirdly the stress ratio by cyclic triaxial test was compared with that obtained from SPT N-value as a kind of empirical methods. It was found that the effect of sample disturbance was relatively small when SPT N-value was less than 20, but there were large differences in safety factor and resistance of liquefaction in soil by the effects of disturbance and remolding when SPT N-value was more than 20.

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