Earticle

지진 발생시에 비교적 큰 규모의 피해를 일으킬 수 있는 것이 지반의 액상화(liquefaction) 발생이다. 지 반의 액상화 현상에 대한 연구는 1960년대 이후 세계적으로 괄목할 만한 성과를 얻어왔으며, 최근, 우리나 라에서도 본격적으로 현장에서 적용하고 있다. 본 연구를 통하여 현장에서 액상화 평가 및 대책공법 적용 까지의 과정을 분석할 수 있었다. 본 연구결과는 향후 유사한 현장에서 적용 가능할 것으로 판단된다.

본 연구에서는 강우침투특성을 규명하기 위해 모암의 성질이 다른 풍화토를 대상으로 침투모형시험 과 수치해석을 실시하여 풍화토별 간극수압 변화와 강우강도에 따른 간급수압 변화양상을 분석하였 다. 침투모형시험 장치는 자체 제작한 1차원 침투모형시험장비를 이용하였으며, 수치해석은 침투모 형시험장비와 동일한 실내시험 조건 및 경계조건으로 모델링하여 분석하였다. 모형시험 및 수치해 석 결과 동일한 강우강도를 적용한 결과 습윤전선이 컬럼하부에 도달하는 시간차는 유사하게 나타 났으며, 투수계수가 크면 침투능 또한 높게 나온다는 사실을 파악할 수 있었다, 또한 강우강도변화에 따라 습윤전선의 진행이 빠르게 진행됨을 파악할 수 있었다. 이러한 분석결과를 통해 지반의 투수계 수, 강우강도와 지속시간은 지반의 침투과정에 영향을 주는 주요 인자임을 확인할 수 있었다. 이러한 침투 메커니즘은 사면 안정해석에 적용되며, 지반의 액상화(지진)에 의한 위험도 평가에 응용될 수 있다.

This study conducted a rainfall infiltration test for weathered soils of different parent rocks in order to investigate infiltration characteristics. The changing pattern of pore water pressure was identified and compared with the numerical analysis results to analyze ground infiltration characteristics in relation to rainfall characteristics. The results of rainfall infiltration test and numerical analysis showed that the infiltration capacity became higher when the infiltration coefficient of weathered soil was large given that the same rainfall intensity was applied. Additionally, it was found that the movement of wetting front was fast in accordance with the changing rainfall intensity. The analysis results indicated that ground infiltration coefficient, rainfall intensity and duration were the major factors influencing ground infiltration process.

Design of Reverse Stirling Cycle based refrigerator can be predicted by Schmidt theory as a useful tool and by experiment it is found that for practical purposes the power and efficiency predicted by this analysis are about 35% of the actual values. Therefore, appropriate provision is to be made for getting the realistic result with the minimum deviation. The present paper first investigates the suitability of application of Schmidt design analysis for standard ZIF-1002 and PLN-106 Single cylinder Cryogenerator model. As the result is found to be optimistic, the same design procedure is applied for the design of a separate Cryogenerator for generating a cooling effect which is sufficient to produce 7 kg per hour liquid nitrogen using an indigenous condenser of 80% effectiveness. The paper describes all the details of the design methodologies and relevant results are found to be satisfactory.

This paper presents the design of a re-liquefaction system as a BOG (boil-off gas) handling process in liquid hydrogen transport vessels. The total capacity of the re-liquefaction system was assumed to be 3 ton/day, with a BOR (boil-off rate) of 0.2 %/day inside the cargo. The re-liquefaction cycle was devised using the He-Brayton Cycle, incorporating considerations of BOG capacity and operational stability. The primary components of the system, such as compressors, expanders, and heat exchangers, were selected to meet domestically available specifications. Case studies were conducted based on the specifications of the components to determine the optimal design parameters for the re-liquefaction system. This encompassed variables such as helium mass flow rate, the number of compressors, compressor inlet pressure and compression ratio, as well as the quantity and composition of expanders. Additionally, an analysis of exergy destruction and exergy efficiency was carried out for the components within the system. Remarkably, while previous design studies of BOG re-liquefaction systems for liquid hydrogen vessels were confined to theoretical and analytical realms, this research distinguishes itself by accounting for practical implementation through equipment and system design.

This paper reviews the development status of magnetic refrigeration system for hydrogen liquefaction. There is no doubt that hydrogen is one of most important energy sources in the near future. In particular, liquid hydrogen can be utilized for infrastructure construction consisting of storage and transportation. Liquid hydrogen is in cryogenic temperatures and therefore high efficient liquefaction method must be studied. Magnetic refrigeration which uses the magneto-caloric effect has potential to realize not only the higher liquefaction efficiency > 50 %, but also to be environmentally friendly and cost effective. Our hydrogen magnetic refrigeration system consists of Carnot cycle for liquefaction stage and AMR (active magnetic regenerator) cycle for precooling stages. For the Carnot cycle, we develop the high efficient system > 80 % liquefaction efficiency by using the heat pipe. For the AMR cycle, we studied two kinds of displacer systems, which transferred the working fluid. We confirmed the AMR effect with the cooling temperature span of 12 K for 1.8 T of the magnetic field and 6 second of the cycle. By using the simulation, we estimate the total efficiency of the hydrogen liquefaction plant for 10 kg/day. A FOM of 0.47 is obtained in the magnetic refrigeration system operation temperature between 20 K and 77 K including LN2 work input.

우리나라에는 2017년 11월 15일 경상북도 포항시에서 규모 5.4의 지진이 일어났다. 이로 인하여 우리 나라에서는 처음으로 액상화 현상이 발생하게 되었다. 이에 대한 정책적인 대책이 부재한 실정이다. 그에 반해 우리나라에서 가장 많이 발생하는 풍수해재해에 대한 보험제도와 지원제도에 대해서는 잘 정리가 되어있다. 본 연구에서는 일본 내각부 액상화 지원대책에 지원금액 산정방법과 적용사례, 지자체의 지원대책 등을 비교⋅분석도 함께 실시하여 우리나라 풍수해 보험제도와 일본의 액상화 지원제도를 반영하여 액상화정책제도의 기초적인 자료를 제공하고자 한다.

An earthquake of magnitude 5.4 occurred on November 15, 2017 in Pohang, Gyeongbuk Province, which caused the liquefaction for the first time in Korea. In Korea, while there is no policy measure to deal with the liquefaction phenomenon, the insurance and compensation system for flood damage is well designed. This study analyzed the policy support measures for liquefaction by the Japan Cabinet Office, including the method of calculating compensation amount, application cases, and compensation policies of the local governments in Japan, and compared with the insurance and compensation system for flood damage in Korea. This study provides basic data to develop policies to respond to liquefaction in Korea, based on the comparison of disaster support systems in Korea and Japan.

The purpose of this analytic study is to design and examine an efficient hydrogen liquefaction cycle by using a pre-cooler. The liquefaction cycle is primarily comprised of a pre-cooler and a refrigerator. The fed hydrogen gas is cooled down from ambient temperature (300 K) to the pre-cooling coolant temperature (either 77 K or 120 K approximately) through the pre-cooler. There are two pre-cooling methods: a single pre-coolant pre-cooler and a cascade pre-cooler which uses two levels of pre-coolants. After heat exchanging with the pre-cooler, the hydrogen gas is further cooled and finally liquefied through the refrigerator. The working fluids of the potential pre-cooling cycle are selected as liquid nitrogen and liquefied natural gas. A commercial software Aspen HYSYS is utilized to perform the numerical simulation of the proposed liquefaction cycle. Efficiency is compared with respect to the various conditions of the heat exchanging part of the pre-cooler. The analysis results show that the cascade method is more efficient, and the heat exchanging part of the pre-coolers should have specific UA ratios to maximize both spatial and energy efficiencies. This paper presents the quantitative performance of the pre-cooler in the hydrogen liquefaction cycle in detail, which shall be useful for designing an energy-efficient liquefaction system.

The purpose of this analytic study is to design and examine an efficient hydrogen liquefaction cycle by using a pre-cooler. The liquefaction cycle is primarily comprised of a pre-cooler and a refrigerator. The fed hydrogen gas is cooled down from ambient temperature (300 K) to the pre-cooling coolant temperature (either 77 K or 120 K approximately) through the pre-cooler. There are two pre-cooling methods: a single pre-coolant pre-cooler and a cascade pre-cooler which uses two levels of pre-coolants. After heat exchanging with the pre-cooler, the hydrogen gas is further cooled and finally liquefied through the refrigerator. The working fluids of the potential pre-cooling cycle are selected as liquid nitrogen and liquefied natural gas. A commercial software Aspen HYSYS is utilized to perform the numerical simulation of the proposed liquefaction cycle. Efficiency is compared with respect to the various conditions of the heat exchanging part of the pre-cooler. The analysis results show that the cascade method is more efficient, and the heat exchanging part of the pre-coolers should have specific UA ratios to maximize both spatial and energy efficiencies. This paper presents the quantitative performance of the pre-cooler in the hydrogen liquefaction cycle in detail, which shall be useful for designing an energy-efficient liquefaction system.

This study presents a dynamic simulation-based evaluation of a large-scale helium compressor test system developed for a 5-ton-per-day (TPD) hydrogen liquefaction plant. A one-dimensional transient simulation tool, EcosimPro, equipped with the CryoLib library was used to model the thermofluid behavior of the helium circulation loop and investigate start-up and pressure-control strategies relevant to helium refrigeration systems in cryogenic processes. The analysis focused on the coordinated operation of three pressure control valves—PCV501, PCV504, and PCV505—that regulate the suction and discharge pressures of the compressor. Through a series of dynamic simulations, appropriate control logic for stable pressurization and pressure regulation was derived. Sensitivity analysis further revealed that an initial loop pressure between 7 and 10 barA yields the most stable start-up condition. These findings demonstrate the usefulness of dynamic modeling using EcosimPro–CryoLib for optimizing control strategies in helium-based thermofluidic systems and provide valuable guidance and reference data for the future operation of hydrogen liquefaction infrastructure.

A vacuum system is designed for thermal insulation of a 10 ton/day class air liquefaction cold box for liquid air energy storage. The vacuum system is composed of a turbomolecular pump, a backing pump and vacuum piping for the vacuum pumps. The turbomolecular pump is in combination with the backing pump for pumping capacity. The vacuum piping is designed with system installation conditions, such as distance from the cold box, connections to vacuum pumps and installation space. The capacity of the vacuum pump combination, namely pumping speed, is determined by analysis of the vacuum system, and pump-down time to 1×10-5 mbar is estimated. Vacuum piping conductance, system pumping speed and outgassing rate are calculated for the pumpdown time with the ultimate pumping speed range of the vacuum pump combination of 1400 – 2300 l/s. Although the pump-down time gets shorter by larger capacity vacuum pumps, it mainly depends on target vacuum degree and outgassing rate in the cold box. The pump-down time is estimated as 3 – 6 hours appropriate for cold box operation for the pumping speed range. Considering the outgassing rate has uncertainty, the vacuum pump combination with pumping speed of 1900 l/s is chosen for the vacuum system, which is middle value of the pumping speed range.

2025년 2월 18일 소방청 보도자료에 의하면, 최근 5년간(2020∼2024년) 공사장 화재는 총 2천732건으로 연평균 546건이 발생했는데, 부주의가 2,049건(75%)로 가장 많았고, 부주의 세부원인별로는 용접·절단·연마가 1,300건(63.4%)로 가장 많았 다고 하였다. 화재 예방을 위해 관련법적기준, 관리실태를 고찰하고 문제점 및 개선방안을 제시하였다. 불티방지포 개선으로 63.4%의 화재 예방의 효과가 기대된다.

연구목적: 이 논문에서는 인천 해안 매립 지반에 대한 액상화 평가를 위하여 장주기의 Hachinohe 지진파와 단주기의 Ofunato 지진파에 대하여 ProShake 프로그램을 사용하여 지 반응답해석을 수행하였다. 연구방법: 지반응답해석 결과와 수정 Seed and Idriss의 방법을 이용하여 액상화 평가를 수 행하였다. 각 지점의 액상화 평가 결과를 대표할 수 있는 지표로 Iwasaki가 제시한 액상화 가능성 지수를 산정하였다. 또한, 액상화 구역도 작성을 위한 정량적인 지표로서 등가 액상 화 안전율을 이용하였다. 연구결과: 이 논문에서는 액상화 가능지수와 등가 액상화 안전율을 이용하여 인천 해안 매 립지역을 대상으로 액상화 구역도를 작성하였다. 결론: 구역도 작성 결과, 액상화 가능지수와 등가 액상화 안전율을 이용하여 작성된 구역도 가 유사한 분포 형태를 보여 이 논문에서 제시한 액상화 구역도 작성 지표로 인천 해안 매립 지역의 액상화 구역도를 작성할 경우 이용에 편리할 것으로 판단된다.

Purpose: This study was carried out to evaluate the liquefaction potential of the land reclamation area in Incheon by using the ProShake program for long frequency Hachinohe seismic wave and short frequency Ofunato seismic waves to interpret ground response. Method: The interpretation results and the Modified Seed and Idriss method were used to evaluate the liquefaction potential. The liquefaction potential index which proposed by Iwasaki was calculated to be used as a guide line to represent the liquefaction evaluation results at the given location. The equivalent liquefaction factor of safety presented by Kang(1999) was used as a quantitative index to draw up the mapping of liquefaction potential. Results: This paper presents the mapping of liquefaction potential for the Incheon seaside reclamation area using both the liquefaction potential index and the equivalent liquefaction factor of safety. Conclution: As a result, the mapping of liquefaction based on the liquefaction potential index and equivalent liquefaction factor of safety shows similar distribution pattern.

The LNG carriers have been propelled by steam turbines and the LNG boil-off(BOG) has been used as fuel or vented. However, as the alternative propulsion systems such as diesel engines are being equipped on the LNG carriers for better fuel efficiency, a need for the LNG BOG re-liquefaction system that liquefies the BOG and sends the liquid BOG back to the LNG cargo has arisen in recent years. This study investigates the design of the BOG re-liquefaction system based on the reverse Brayton refrigeration cycle. The thermodynamic and heat exchanger analysis are carried out and the limitations to the system performance are discussed.

General process for waste vinyl pretreatment system is consisted of separating, crushing, washing, drying and recovering impurities. However, there are problems such as wastewater when washing of waste vinyl. In order to solve these problems we have developed new dry type cleaning system. This system consists of five equipment : 1) Hydraulic cutter to cut in 1m size, 2) 1st crusher to cut in 20～30cm size, 3) 2nd crusher to cut in 3～8cm size. 4) Separation to recovering impurities. 5) Thermal fiow dryer to dry.

Adiabatic demagnetization refrigerator (ADR) for hydrogen re-liquefaction operating between 24 K and 20 K has been designed. Dy0.9Gd0.1Ni2, whose Curie temperature is 24 K, is selected as a magnetic refrigerant. The magnetic refrigerant powder is sintered with oxygen-free high purity copper (OFHC) powder to enhance its effective thermal conductivity as well as to achieve relatively high frequency. A perforated plate heat exchanger (PPHE) operated with forced convection is utilized as a heat switch. The forced convection heat switch is expected to have fast response relative to a conventional gas-gap heat switch. A conduction-cooled high TC superconducting (HTS) magnet is employed to apply external magnetic field variation on a magnetic refrigerant. 2nd generation GdBCO coated conductor HTS tape with Kapton® insulation (SUNAM Inc.) will be utilized for the HTS magnet. The magnetization and demagnetization processes are to be achieved by the AC operation of the HTS magnet. The designed magnetic field and target ramp rate of the HTS magnet are over 4 T with 180 A and 0.4 T/s, respectively. AC loss distribution on HTS magnet is theoretically estimated.

지반의 액상화 현상을 방지하기 위하여 모래다짐말뚝공사를 실시하는 경우에 일부 지층의 관입저항의 증대로 인해 타설장비에 과도한 부하가 발생하고 관입속도가 저하되는 경우가 있다. 이러한 상황이 발생되 면 관입장비가 전도의 위험이 증가하여 매우 위험할 수 있다. 본 연구에서는 이러한 상황에 대한 시공성에 대하여 사례를 분석하였다.