• Geomechanics and Engineering
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• 제11권3호
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• pp.345-359
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• 2016

In order to investigate the influence of the interfacial angel on failure characteristics and mechanism of combined coal-rock mass, 35 uniaxial/biaxial compressive simulation tests with 5 different interfacial angels of combined coal-rock samples were conducted by PFC2D software. The following conclusions are drawn: (1) The compressive strength and cohesion decrease with the increase of interfacial angle, which is defined as the angle between structure plane and the exterior normal of maximum principal plane, while the changes of elastic modulus and internal friction angle are not obvious; (2) The impact energy index $K_E$ decreases with the increase of interfacial angle, and the slip failure of the interface can be predicted based on whether the number of acoustic emission (AE) hits has multiple peaks or not; (3) There are four typical failure patterns for combined coal-rock samples including I (V-shaped shear failure of coal), II (single-fracture shear failure of coal), III (shear failure of rock and coal), and IV (slip rupture of interface); and (4) A positive correlation between interfacial angle and interface effect is shown obviously, and the interfacial angle can be divided into weak-influencing scope ($0-15^{\circ}$), moderate-influencing scope ($15-45^{\circ}$), and strong-influencing scope (> $45^{\circ}$), respectively. However, the confining pressure has a certain constraint effect on the interface effect.

• 마이크로전자및패키징학회지
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• 제15권1호
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• pp.51-58
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• 2008

본 논문에서는 PTC 서미스터의 전기적 온도특성을 이용하여 각종 전기화재 및 전기사고를 예방 보호하는 방재시스템에 대해 연구하였다. PTC(Positive Temperature Coefficient) 서미스터는 온도변화에 따른 저항특성이 정 (+)온도계수를 갖는 특징이 있다. PTC서미스터는 정온도계수를 갖는 $BaTiO_3$계 세라믹스의 정방정계-입방정계 구조를 가지고 상변이점인 큐리(Curie)온도 이상으로 온도가 증가하면 저항이 급격히 증가하는 현상을 보인다. 본 논문에서는 이러한 정저항 온도특성과 자체 발열특성을 갖는 PTC 서미스터를 전기단락사고나 과부하사고 등 전기사고의 감지센서로 이용하여 전기화재사고를 예방하는 제어시스템에 대해 제안하였다. 그 결과 기존에 상용되는 차단기들의 빈번한 오동작과 저 신뢰성, 저속응성 등으로 발생되는 전기화재 및 전기재해의 문제점들을 해결하였다. 또한 제안한 방재시스템의 다양한 실험결과를 통해 이론적 해석의 타당성을 입증하였다.

• 한국지진공학회논문집
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• 제2권2호
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• pp.35-44
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• 1998

최근의 중.소규모의 연이은 지진활동은 한반도도 지진에 대하여 안전지대는 아닌 것으로 생각되고 있으며, 1995년 일본의 Kobe 지진 대 참사는 국내에도 지진에 관한 많은 관심을 고조시키고 있다. 그러나, 국내의 구조물의 내진설계를 위한 사용되는 지진파에 대한 연구는 매우 미흡하며, 최근까지도 국내에서는 외국의 설계용 지진파를 그대로 사용하거나 설계응답스펙트럼을 이용하고 있는 실정이다. 본 논문에서는 국내지진파의 물리적 특성, 즉, 주기-빈도 분포, 확률밀도분포, Fourier Spectrum 및 응답스펙트럼을 구하여 비교.분석하였다. 또한 이상화된 인공지진파를 산출하여 이를 현재 교통량의 폭발적인 증가와 도로의 선형성을 이유로 사각을 가진 교량구조물이 많이 건설되고 있는바, 70$^{\circ}$사각슬래브교에 대한 지진해석을 수행하여 인공지진의 합리적 해석 횟수를 규명하였다.

• 한국지반환경공학회 논문집
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• 제14권8호
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• pp.53-60
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• 2013

국내 도로 하부구조의 다짐관리 방법은 상대 다짐도를 구하기 위한 현장밀도 시험과 하중 지지력을 확인하는 평판재하시험을 이용하고 있다. 그러나 이 두 시험방법은 시공현장 관리자의 경험적 판단을 수치화한 것으로 역학적인 근거가 미약한 실정이다. 이러한 문제점을 해결하기 위해 최근 사용되고 있는 회복탄성계수법은 차량하중의 반복재하 조건에서 유발되는 포장재료의 응력-변형 상태를 합리적으로 반영할 수 있는 합리적인 포장구조 설계법으로 평가되고 있다. 그러나 회복탄성계수를 측정하는 방법이 어렵고 시간이 많이 소요되는 등 많은 문제점이 있으므로 이를 대체할 수 있는 간편한 시험법으로 최근 소형충격재하시험법이 제안되고 있다. 따라서 본 연구에서는 노상과 보조기층의 시공 및 유지관리 현장의 변형계수를 신속하고 간편하게 측정할 수 있는 동평판재하시험을 이용하여 도로 하부지층의 다짐관리 가능성을 판단하고 정적재하시험결과를 분석하여 관계식을 제안하였다.

• 한국터널지하공간학회 논문집
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• 제15권4호
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• pp.375-385
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• 2013

본 논문에서는 천매암을 중심으로 저변성퇴적암류에 속하는 암석을 대상으로 암석학적 특징과 풍화도의 상관성에 대하여 분석하였다. 현장 지질조사를 통하여 암석의 풍화도를 결정하였고, 구성암석의 강도 값을 추정하기 위하여 슈미트해머 테스트를 실시하였다. 9개 시료의 현미경 박편 관찰을 통하여 주구성광물의 부피비와 엽리의 간격을 측정하였다. 암석시료의 현미경 분석 결과에 의하면 풍화도가 낮을수록 풍화에 강한 석영성분이 많고, 풍화도가 높을수록 풍화에 약한 운모성분이 많은 것으로 나타났다. 또한 엽리 간격이 좁을수록 강도는 낮고 풍화도는 높은 것으로 나타났다.

• 대한안전경영과학회지
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• 제24권4호
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• pp.49-59
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• 2022

Mt. Umyeon is a low-altitude mountain near a residential area, and the actual forest area is not large due to the fact that development for use as a living green space is being completed and in progress across the mountain, so the buffering action for landslides was weak. The unit was located at the top of Mt. Umyeon, and there were reports of contents related to the military unit in some accident areas. Some experts suggested that the landslide that started on the cut side of the unit could be one of the causes of the landslide at Mt. Umyeon. It is presumed that there was a sudden collapse of trees that had fallen due to erosion inside the valley. In the case of the Umyeon landslide, localized torrential rain is the biggest cause, but the fact that it suffered a lot of damage is the result of no preemptive measures. In particular, it can be said that the damage was caused by the concentration of residential and commercial facilities due to the unplanned urban expansion without prior review of the feng shui geography of settlement areas. The important lesson we have learned is that we should recognize nature as living things and live in harmony and coexistence between humans and nature through understanding and cooperation. Adapting to changes in the environment can survive, but if it doesn't, it will be slaughtered. As such, geography influences changes in feng shui. Changes in feng shui have a profound effect on not only humans but also the natural ecosystem.

• 한국농촌건축학회논문집
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• 제16권1호
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• pp.95-102
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• 2014

The number of industrial accident victims in the construction industry accounts for 1/3 of those in the entire industries and about 30% of the total compensation costs are spent in the construction industry. As such, the construction industry is a typical industry causing numerous safety accidents. This study analyzes the status of industrial accidents in small scale construction sites to build maximum five-story buildings by examining statistical data for the past five years, investigating those construction sites and conducting interviews with the workers. This study also seeks the causes of and measures for industrial accidents in the small scale construction industry through comparison with relevant systems. The findings are as follows: (1) To reduce hazard rate, shaping the working environment and safety measures that take into account the physically weak classes of the middle aged and the aging are urgently required, because 62.9% of the industrial accidents in the construction industry occurred to those who are 50 years of age or older. (2) The hazard rate at small scale construction sites with less than 10 construction workers accounts for 55% of that of the entire industries. The government, in this context, needs to support finance or technology and improve system by selecting the small scale construction sites, where industrial accidents occur frequently. (3) Because the hazard rate of unskilled workers with less than 6 months of work experience accounts for 90.95% of the total, safety education needs to be concentrated on those unskilled workers. (4) The relevant standards need to be segmented and revised and bolstered, given that 64.79% of death disaster in the construction industry occurs in the temporary structures including scaffolds and ladders.

• Geomechanics and Engineering
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• 제31권6호
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• pp.557-571
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• 2022

Landslides are often triggered by weak interlayers initiated in tailings dam foundations, and hazards gradually occur. This is serious for landslides in high tailings dams due to their high potential energy. Tailing samples with a fine-grained interlayer at a set dip angle were prepared. Consolidated undrained (CU) triaxial shear tests were carried out by using a high-pressure triaxial apparatus. The results were compared with the results under a low confining pressure. Four reasons were summarized for high tailings dams more prone to instability than low dams. The shear strength of the samples with dipping interlayers decreases with increasing dip angle. An obvious straight drop in the stress path after the peak occurs in samples with dipping interlayers at an angle of 60°. The effect of the interlayer on the mechanical behaviour of tailings is very sensitive, especially for the sample with a dipping interlayer at an angle of 60°. Shear slipping along the interlayer should be given more attention in tailings dams. Compared with the results under low confining pressure, the stress decreases continuously for the samples with dipping interlayers at large angles under high confining pressure. The positive pore pressure, which reduces the effective stress, occurred in tailings samples under high confining pressure. The residual strength of tailings under high confining pressure is smaller than that under low confining pressure. These factors increase the dam break risk and the disaster impact for high tailings dams.

• Earthquakes and Structures
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• 제14권4호
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• pp.337-347
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• 2018

This paper presents some shaking table tests conducted on a 1/4-scaled model with 5-story steel reinforced concrete (SRC) spatial frame with irregular section columns under a series of base excitations with gradually increasing acceleration peaks. The test frame was subjected to a sequence of seismic simulation tests including 10 white noise vibrations and 51 seismic simulations. Each seismic simulation was associated with a different level of seismic disaster. Dynamic characteristic, strain response, acceleration response, displacement response, base shear and hysteretic behavior were analyzed. The test results demonstrate that at the end of the loading process, the failure mechanism of SRC frame with irregular section columns is the beam-hinged failure mechanism, which satisfies the seismic code of "strong column-weak beam". With the increase of acceleration peaks, accumulated damage of the frame increases gradually, which induces that the intrinsic frequency decreases whereas the damping ratio increases, and the peaks of acceleration and displacement occur later. During the loading process, torsion deformation appears and the base shear grows fast firstly and then slowly. The hysteretic curves are symmetric and plump, which shows a good capacity of energy dissipation. In summary, SRC frame with irregular section columns can satisfy the seismic requirements of "no collapse under seldom earthquake", which indicates that this structural system is suitable for the construction in the high seismic intensity zone.

• 한국정보전자통신기술학회논문지
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• 제11권6호
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• pp.793-799
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• 2018

CCD카메라는 방사선에 쉽게 열화되어 고방사선구역에서는 촬상관을 이용한 일체화된 카메라가 사용되고 있다. 이를 방사선에 강한 전자부품을 사용한 카메라헤드부와 방사선에 약한 TR, IC등을 사용한 원격제어부로 분리제작한 내 방사선 카메라시스템을 구현하였다. 실험결과 전자부품 중 가장 먼저 손상된 것은 수평 및 수직 동기 발생 IC이었으며 $2{\times}10^5{\sim}10^6rad$의 방사선이 누적되면 정상적인 기능이 상실됨을 확인하였다. 또한 원격화를 위한 신호전송 케이블은 입출력 버퍼회로를 부가하고 쉴드와 케이블의 폐루프면적을 감소시켜 신호 손실보정 및 노이즈를 제거하였다. 따라서 전체의 시스템을 교체하는 것이 아니라 카메라 헤드부분만을 교체하여 사용할 수 있으므로 실용적이며 관리 유지비용이 많이 절감 될 것으로 기대된다.