• 제목/요약/키워드: SAFE-ROCK

검색결과 165건 처리시간 0.026초

Quantitative Determination of Cristobalite Content in Diatomite and Filtered Food (규조토와 여과식품 중 크리스토발라이트의 정량분석)

  • Jeong, Gi Young
    • Journal of the Mineralogical Society of Korea
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    • 제32권4호
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    • pp.313-321
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    • 2019
  • Diatomite is a silicic porous sedimentary rock composed of diatom frustules, used for filtration aid, filler, absorbent, abrasive, carrier, insulator, and fertilizer. During the calcination of diatomite to improve physical properties for filtration-aid application, amorphous silica is transformed to cristobalite. X-ray diffraction and scanning electron microscopy studies were carried out for 17 diatomite samples, showing that 16 diatomite samples contain cristobalite in the range of 6~100 %. Concentration of respirable cristobalite in air is regulated as harmful substances, but the residual cristobalite in food is treated as generally safe substance. The determination procedure of cristobalite content in food was established for managing food safety. Calibration curve of cristobalite filtered on silver membrane were obtained by X-ray diffraction. The lower limit of quantification was evaluated as 2.7 mg. The cristobalite was not detected in the analyses of selected food samples using the established procedure.

Preliminary Study for Non-destructive Measurement of Stress Tensor on H-beam in Tunnel Support System using a Magnetic Anisotropy Sensor (자기 이방성 응력측정법을 활용한 터널 지보 구조물의 비파괴계측에 관한 기초적 연구)

  • Lee, Sang-Won;Akutagawa, Shinichi;Kim, Young-Su;Jin, Guang-Ri;Jeng, Ii-Han
    • Proceedings of the Korean Geotechical Society Conference
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    • 한국지반공학회 2008년도 춘계 학술발표회 초청강연 및 논문집
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    • pp.766-777
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    • 2008
  • Currently in increasing number of urban tunnels with small overburden are excavated according to the principle of the New Austrian Tunneling Method (NATM). Successful design, construction and maintenance of NATM tunnel demands prediction, control and monitoring of ground displacement and support stress high accuracy. A magnetic anisotropy sensor is used for nondestructive measurement of stress on surfaces of a ferromagnetic material, such as steel. The sensor is built on the principle of the magneto-strictive effect in which changes in magnetic permeability due to deformation of a ferromagnetic material is measured in a nondestructive manner, which then can be translated into the absolute values of stresses existing on the surface of the material. This technique was applied to measure stresses of H-beams, used as tunnel support structures, to confirm expected measurement accuracy with reading error of about 10 to 20 MPa, which was confirmed by monitoring strains released during cutting tests The results show that this method could be one of the promising technologies for non-destructive stress measurement for safe construction and maintenance of underground rock structures encountered in civil and mining engineering.

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Non-destructive Measurement of H-beam in Support System using a Magnetic Anisotropy Sensor (자기이방성 응력측정법을 이용한 강아치 지보구조물의 비파괴 계측)

  • Yoo, Ji-Hyeung;Moon, Hong-Deuk;Lee, Jae-Ho;Kim, Dae-Sung;Kim, Hyuk
    • Proceedings of the Korean Geotechical Society Conference
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    • 한국지반공학회 2010년도 춘계 학술발표회
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    • pp.1392-1397
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    • 2010
  • Currently in increasing number of urban tunnels with small overburden are excavated according to the principle of the New Austrian Tunneling Method(NATM). Successful design, construction and maintenance of NATM tunnel demands prediction, control and monitoring of ground displacement and support stress high accuracy. A magnetic anisotropy sensor is used for non-destructive measurement of stress on surfaces of a ferromagnetic material, such as steel. The sensor is built on the principle of the magneto-strictive effect in which changes in magnetic permeability due to deformation of a ferromagnetic material is measured in a non-destructive manner, which then can be translated into the absolute values of stresses existing on the surface of the material. This technique was applied to measure stresses of H-beams, used as tunnel support structures, to confirm expected measurement accuracy with reading error of about 10 to 20MPa, which was confirmed by monitoring strains released during cutting tests The results show that this method could be one of the promising technologies for non-destructive stress measurement for safe construction and maintenance of underground rock structures encountered in civil and mining engineering.

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A Study on the Behaviour of an Earth and Rockfill Dam Due to Reservoir Water (저수변화에 따른 사력댐의 거동 연구)

  • Shin, Jong-Ho
    • Journal of the Korean Geotechnical Society
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    • 제19권6호
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    • pp.61-70
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    • 2003
  • The behaviour of an earth and rock-fill dam is complicated due to reservoir water and various materials in zoned dams. Different materials with a wide range of permeability and seasonal variation of reservoir water result in the time dependent post-constructional behaviour. In aged dams it is often required to control water level to keep the dams safe. In this case information on the post-constructional dam behaviour is important. However, present geotechnical knowledge does not fully support the occasion. In this study the post-constructional behaviour of a dam is investigated using coupled finite element models for series of idealized water reservoir cases: impoundment, draw down, seasonal fluctuation with different rising and falling speeds. Numerical results were analysed in respect of geotechnical parameters such as load transfer, hydraulic fracturing potential and stress paths. It is shown that the control of water level is an important factor while operating dams.

Design consideration and explosion safety of underground ammunition storage facilities (지하탄약고의 설계요소 및 폭발안전 연구)

  • Kim, Oon-Young;Lee, Myung-Jae;Kim, Min-Seok;Kim, Joon-Youp;Joo, Hyo-Joon
    • Journal of Korean Tunnelling and Underground Space Association
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    • 제5권1호
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    • pp.55-70
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    • 2003
  • Ammunition magazine, which is installed on the ground, has difficulty in protecting from the external attack, and accidental explosion should cause great damage to the life and property. For these reasons, it is needed to develop underground magazine that it has the advantages of safety, security and maintenance. This paper introduce the design case for blasting facilities, which should resist blasting pressure, as well as layout of underground magazine, which takes a safety for explosion and a working space of loading/unloading machine into consideration. On the layout, in case of ${\bigcirc}{\bigcirc}$ underground magazine, put three storage chambers in position almost parallel with principle stress direction, where less effected on discontinuity and hard rock area. Also, secured safe distance according to safety criteria of the Defense Ministry, and verified suitable layout by trace simulation for loading/unloading machine on working stage. Blasting design was performed on evaluation of maximum blast pressure between donar and acceptor chambers, and design condition for blast door, valve, etc. Diminution facilities against explosion, such as thrust block or debris trap, determined its size after plan in accordance with blasting criteria and calculation by structural analysis.

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Microbial contamination including Vibrio cholerae in fishery auction markets in West Sea, South Korea

  • Choi, Yukyung;Lee, Yewon;Lee, Soomin;Kim, Sejeong;Lee, Jeeyeon;Ha, Jimyeong;Oh, Hyemin;Shin, Il-Shik;Yoon, Yohan
    • Fisheries and Aquatic Sciences
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    • 제22권11호
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    • pp.26.1-26.7
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    • 2019
  • Background: The monitoring of pathogens of fishery auction markets is important to obtain safe fishery products regarding hygiene and sanitation. In this study, aerobic, coliform, Escherichia coli, and Vibrio cholerae were monitored in the fishery products and environmental samples obtained from fishery auction markets. Methods: The fishery products (flounder, octopus, skate, rock cod, sea bass, snail, monkfish, flatfish, comb pen shell, corb shell, conger eel, hairtail, croaker, and pilchard) were placed in filter bags, and the environmental samples (samples from the water tanks at the fishery auction markets, seawater from the fishery distribution vehicles, ice from wooden or plastic boxes, and surface samples from wooden and plastic boxes used for fish storage) were collected. Aerobic bacteria, E. coli, and coliform in the samples were enumerated on aerobic count plates and E. coli/coliform count plates, respectively. For V. cholerae O1 and V. cholerae non-O1 quantification, most probable number (MPN)-PCR analysis was performed. Results: Aerobic and coliform bacteria were detected in most samples, but E. coli was not detected. Wooden boxes were contaminated with high levels of aerobic and coliform bacteria in all seasons (spring, summer, and fall). During fall, V. cholerae non-O1 were detected in snails, hairtails, croakers, flatfishes, pilchards, plastic boxes, and water samples. Conclusions: These results indicate an increased prevalence of V. cholerae contamination in fishery products in fall, including food contact samples, which can be vehicles for cross-contamination.

Study on Establishing a Blast Guideline for Securing an Underground Crusher Room from Ground Vibrations (지하 조쇄실의 진동 안정성 확보를 위한 발파지침 수립 연구)

  • Choi, Byung-Hee;Ryu, Chang-Ha;Kim, Hyun-Woo;Kang, Myoung-Soo
    • Explosives and Blasting
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    • 제33권2호
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    • pp.15-24
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    • 2015
  • In general, blast vibrations could make underground cavern unstable by causing relative movements between the surrounding rock blocks that are divided by discontinuities such as joints and faults around the cavern. In the study, a blast guideline was established to obtain the stability of a large-scale cavern for underground crusher room in an open pit limestone mine in Korea. The guideline was suggested in the form of a standard calculation method of the maximum charge per delay for a safe blast. The allowable level of peak particle velocity for the cavern was determined based on the result of a numerical analysis using FLAC2D. The ground vibration data required for the study was obtained from field measurements.

Case Study on the Tunnel Collapses during the Construction and Application of Geotechnical Investigation (터널 시공 중 지반 관련 사고 사례의 원인 분석과 지반 조사 결과의 활용에 관한 검토)

  • Park, Nam-Seo;Lee, Chi-Mun;Gang, Sang-Ho
    • Proceedings of the Korean Geotechical Society Conference
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    • 한국지반공학회 1998년도 지반조사위원회 봄 학술세미나
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    • pp.47-60
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    • 1998
  • It is considered in this paper that the main causes of tunnel collapse during the construction were the insufficiency of data of geotechnical investigations, or their limits due to special ground condition such as its heterogeneity and anisotropy It is thought that safety of ground can be affected by the geological conditions such as presences of discontinuities in good intact rocks, and considered to be necessary that awareness of the conditions of discontinuities in advance is important to apply adequate reinforcement measures. It is also shown that a serious accident had occurred because of the unawareness of the permeable alluvial deposits at the top of the tunnel. And it is shown that the example of application of the results of geotechnical investigation such as face-mapping, pilot boring etc. during tunnel construction, and a serious deformation of tunnel under special geological condition. Therefore, it is strongly recommended to perform an adequate geotechnical investigation to confirm the geotechnical conditons of ground before design, and supplimentary investigation is also needed depending on conditions for safe and econonic construction.

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Need-to-knows about Digital Implant Surgery (디지털 가이드 수술의 이해와 임상적 적용)

  • Paek, Janghyun;Kwon, Kung-Rock;Kim, Hyeong-Seob;Pae, Ahran;Noh, Kwantae;Hong, Sung-Jin;Lee, Hyeon-jong
    • The Journal of the Korean dental association
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    • 제56권11호
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    • pp.631-640
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    • 2018
  • Nowadays computer-guided "flapless" surgery for implant placement using templates is gaining popularity among clinicians and patients. The advantages of this surgical protocol are its minimally invasive nature, accuracy of implant placement, predictability, less post-surgical discomfort and reduced time required for definitive rehabilitation. Aim of this study is to describe the digital implant protocol, thanks to which is now possible to do a mini-invasive static guided implant surgery. This is possible thanks to a procedure named surface mapping based on the matching between numerous points on the surface of patient's dental casts and the corresponding anatomical surface points in the CBCT data. With some critical points and needing an adequate learning curve, this protocol allows to select the ideal implant position in depth, inclination and mesio-distal distance between natural teeth and or other implants enabling a very safe and predictable rehabilitation compared with conventional surgery. It represents a good tool for the best compromise between anatomy, function and aesthetic, able to guarantee better results in all clinical situations.

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A Case Study on Reinforcement Method by Excavation Adjacent to the Subway Tunnel using Numerical Analysis (수치해석을 통한 지하철 구조물 인접 굴착에 따른 보강공법 적용사례연구)

  • Byun, Yo-Seph;Jung, Kyoung-Sik;Chun, Byung-Sik
    • Journal of the Korean GEO-environmental Society
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    • 제12권9호
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    • pp.5-11
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    • 2011
  • Recently, large and deep excavations are increasing. The damage of adjacent structures due to excavation has steadily increased with increasing construction demand. Especially in urban development and poor conditions, the excavation adjacent to the subway structures has caused a lot of problems. This paper was reviewed that the underground excavation and reinforcement of the status process through a case study on the field. And stability analysis through the case study evaluates applicability for reasonable reinforcement method by numerical analysis. As a result, the strata distribution condition of all 16 sites consisted of landfill from the top and distributed in the order of deposits, weathered soils, weak rock from the bottom. Also, when proceeding the excavation adjacent to structures, the location of site and layer conditions have highly effect on the results of the construction. Therefore, this study was applied reinforcement method to protect damage by excavation. Displacement and settlement were within allowable criterion and hence, stability of structure was analyzed as safe.