• Geomechanics and Engineering
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• 제23권5호
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• pp.441-454
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• 2020

The tunnel collapse, large deformation of surrounding rock, water and mud inrush are the major geological disasters in soft rock tunnel construction. Among them, tunnel collapse has the most serious impact on tunnel construction. Current research backed theories have certain limitations in identifying the collapse risk of soft rock tunnels. Examining the Zhengwan high-speed railway tunnel, eight soft rock tunnel collapse influencing factors were selected, and the combination of indicator weights based on the analytic hierarchy process and entropy weighting methods was obtained. The results show that the groundwater condition and the integrity of the rock mass are the main influencing factors leading to a soft rock tunnel collapse. A comprehensive fuzzy evaluation model for the collapse risk of soft rock tunnels is being proposed, and the real-time collapse risk assessment of the Zhengwan tunnel is being carried out. The results obtained via the fuzzy evaluation model agree well with the actual situation. A tunnel section evaluated to have an extremely high collapse risk and experienced a local collapse during excavation, verifying the feasibility of the collapse risk evaluation model. The collapse risk evaluation model proposed in this paper has been demonstrated to be a promising and innovative method for the evaluation of the collapse risk of soft rock tunnels, leading to safer construction.

• Safety and Health at Work
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• 제2권3호
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• pp.236-242
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• 2011

Objectives: To determine the feasibility of predicting static and dynamic peak back-compressive forces based on (1) static back compressive force values at the lift origin and destination and (2) lifting speed. Methods: Ten male subjects performed symmetric mid-sagittal floor-to-shoulder, floor-to-waist, and waist-to-shoulder lifts at three different speeds (slow, medium, and fast), and with two different loads (light and heavy). Two-dimensional kinematics and kinetics were captured. Linear regression analyses were used to develop prediction equations, the amount of predictability, and significance for static and dynamic peak back-compressive forces based on a static origin and destination average (SODA) backcompressive force. Results: Static and dynamic peak back-compressive forces were highly predicted by the SODA, with R2 values ranging from 0.830 to 0.947. Slopes were significantly different between slow and fast lifting speeds (p < 0.05) for the dynamic peak prediction equations. The slope of the regression line for static prediction was significantly greater than one with a significant positive intercept value. Conclusion: SODA under-predict both static and dynamic peak back-compressive force values. Peak values are highly predictable and could be readily determined using back-compressive force assessments at the origin and destination of a lifting task. This could be valuable for enhancing job design and analysis in the workplace and for large-scale studies where a full analysis of each lifting task is not feasible.

• 비파괴검사학회지
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• 제22권2호
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• pp.149-154
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• 2002

실제 사용 온도 보다 높은 $630^{\circ}C$에서 열처리 시간을 변수로 하여 최대 1000 시간 동안 등온 열처리를 통해 2.25Cr-1Mo 강의 경년열화재를 제작하고 열화에 따른 미세조직과 기계적 특성 변화에 대한 초음파 비파괴평가 법으로 표면 특성평가에 우수한 표면 SH파를 적용하였다. 열화에 따른 초음파의 감쇠와 전파시간 및 웨이블렛을 이용한 음속과 감쇠계수의 주파수 의존성평가를 수행한 결과 열화가 진행됨에 따라서 탄화물은 점차 조대화되고 경도는 감소하였다. 감쇠계수는 열화시간이 증가함에 따라서 증가하였고 전파시간 역시 열화의 초기단계에 급격히 증가했다. 초음파의 감쇠와 경도와는 좋은 상관관계를 나타내어 감쇠계수는 경년열화 평가에 중요한 파라미터임을 알 수 있었다.

• 환경정책연구
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• 제10권1호
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• pp.93-127
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• 2011

현재 전 세계적으로 환경오염과 자원위기 등 문제를 해결하기 위한 친환경 에너지와 관련된 기술 개발 투자가 확대되고 있다. 이러한 기술 개발 프로젝트는 국가적, 대규모적일수록 단일 기술이 아니라 여러 가지의 요소 기술들이 같이 개발되는 형태를 취하게 된다. 그러나 어떠한 기술 조합을 개발하는 것이 좋은지에 대한 의사결정을 하여 주는 방법론은 거의 존재하지 않는 실정이다. 따라서 본 연구의 목적은 최적의 친환경 에너지 기술 조합을 선정하는 방법론을 제안하는 것이다. 개발 기술들을 여러 개의 카테고리로 분류한 다음, 가장 근간이 되는 기준기술을 정하고, 해당 기준기술과의 관련성과 개발 성공에 대한 위험성이라고는 두 가지 차원과 관련성 및 위험성의 상대적 중요도를 고려하여 각 카테고리 별로 최적의 기술을 선정하게 된다. 제안한 선정 방법론의 가능성을 검증하기 위하여 풍력 발전 기술 조합 선정에 대한 사례에 적용해 보았다.

• 환경정책연구
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• 제11권3호
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• pp.67-96
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• 2012

도심 하천복원사업의 정책적 방향을 도출하기 위한 기초연구로서, 이미 사업이 종료된 청계천 복원사업에 대한 사후 비용편익 항목과 분석방안을 제시하고자 한다. 사후 비용편익 항목을 도출하기 위해 사전 비용편익분석의 비용과 편익항목에 대하여 비판적으로 검토하였다. 검토의견과 예비타당성 표준지침, 비용편익분석 이론 등에 근거하여 사후 비용편익 분석방안을 제시하였다. 그 결과, 비용부문에는 보상비, 갈등조정비, 연구 및 홍보비, 감면받은 유지용수, 물 값 등이 포함되었다. 편익부문에는 환경개선편익 추정시 하천의 자연도 평가를 포함한 다속성 평가기법을 적용하도록 제안하였다. 이와 같은 사후 비용편익 항목과 분석방안이 제시됨으로써 도심 하천복원사업의 효율성이 증대되고, 하천복원의 의미에 더 부합되도록 사업을 평가할 수 있다.

• 의료ㆍ복지 건축 : 한국의료복지건축학회 논문집
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• 제23권2호
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• pp.27-35
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• 2017

Purpose: This study analyzed the status of general hospitals as an expanded concept of medical resources including medical staff and equipment. The purpose of this study is to provide a basic for the feasibility study of the scale and establishment of facility guidelines at the planning stage of general hospitals. Methods: The subjects of this study were limited to general hospitals. The status of medical resources was based on the data of the Health Insurance Review and Assessment Service. The number of beds, doctors, nursing grades and major medical equipment were surveyed in 335 general hospitals. Results: 1) The characteristic of general hospitals varies depending on the number of inpatient beds. To be concrete, there were differences in the number of medical staffs and equipments in general hospitals based on 300 500 800 1,000 beds. 2) As the number of hospital beds increases, the number of medical staff increases more than medical equipment and facilities. Medical equipment and facilities remain constant, even when the number of beds increases. On the other hand, the number of medical staff increased about 1.5 times in each level. Implications: Architectural plans for medical staff should be considered differently depending on the number of beds. In particular, architectural planning and facility guidelines should be applied differently based on 300 and 500 beds.

• Earthquakes and Structures
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• 제4권5호
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• pp.451-470
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• 2013

It generally accepted that most building structures shall exhibit a nonlinear response when subjected to medium-high intensity earthquakes. It is currently known, however, that this phenomenon is not properly modelled in the majority of cases, especially at the design stage, where only simple linear methods have effectively been used. Recently, as a result of the exponential progress of computational tools, nonlinear modelling and analysis have gradually been brought to a more promising level. A wide range of modelling alternatives developed over the years is hence at the designer's disposal for the seismic design and assessment of engineering structures. The objective of the study presented herein is to test some of these models in an existing structure, and observe their performance in nonlinear static and dynamic analyses. This evaluation is done by the use of two of a known range of advanced computer programs: SAP2000 and SeismoStruct. The different models will focus on the element flexural mechanism with both lumped and distributed plasticity element models. In order to appraise the reliability and feasibility of each alternative, the programs capabilities and the amount of labour and time required for modelling and performing the analyses are also discussed. The results obtained show the difficulties that may be met, not only in performing nonlinear analyses, but also on their dependency on both the chosen nonlinear structural models and the adopted computer programs. It is then suggested that these procedures should only be used by experienced designers, provided that they are aware of these difficulties and with a critical stance towards the result of the analyses.

• ALGAE
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• 제25권2호
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• pp.89-97
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• 2010

To test the feasibility of using chlorophyll ${\alpha}$ fluorescence to assess the establishment success of seagrass transplants, photosynthetic characteristics of eelgrass Zostera marina transplants were measured using a Diving-pulsed amplitude modulation fluorometer in Jindong Bay on the southern coast of Korea. Maximum quantum yield ($F_v/F_m$), photosynthetic efficiency ($\alpha$), saturating irradiance ($E_k$) and maximum electron transport rate ($ETR_{max}$) of transplants and reference plants in a nearby transplant site were measured using the fluorometer for 5 months. Additionally, shoot morphology, individual shoot weight and productivity of transplants and reference plants were also monitored. Shoot height, leaf weight and productivity of transplants were significantly reduced during the first two or three months after transplantation compared to those of reference plants, and then increased to the levels of reference plants Characteristics of chlorophyll a fluorescence, including $F_v/F_m$, $\alpha$, $E_k$ and $ETR_{max}$ of transplants were also significantly reduced in the initial period, but recovered slightly sooner than shoot morphology or leaf productivity. These results indicated that after transplantation, Z. marina transplant photosynthesis recovered faster than shoot morphology, biomass or productivity. Thus, chlorophyll a fluorescence can be used as an indicator for early assessment of the status of eelgrass transplants without destructive sampling.

• Geomechanics and Engineering
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• 제23권4호
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• pp.339-349
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• 2020

This study investigates the feasibility of using the results of the UPV (ultrasonic pulse velocity) test to assess the UCS (unconfined compressive strength) of unsaturated soil. A series of laboratory tests was conducted on samples of unsaturated lateritic soils of northern Taiwan. Specifically, the unconfined compressive test was combined with the pressure plate test to obtain the unconfined compressive strength and its matric suction (s) of the samples. Soil samples were first compacted at the designated water content and subsequently subjected to the wetting process for saturation and the following drying process to its target suction using the apparatus developed by the authors. The correlations among the UCS, s and UPV were studied. The test results show that both the UCS and UPV significantly increased with the matric suction regardless of the initial compaction condition, but neither the UCS nor UPV obviously varied when the matric suction was less than the air-entry value. In addition, the UCS approximately linearly increased with increasing UPV. According to the investigation of the test results, simplified methods to estimate the UCS using the UPV or matric suction were established. Furthermore, an empirical formula of the matric suction calculated from the UPV was proposed. From the comparison between the predicted values and the test results, the MAPE values of UCS were 4.52-9.98% and were less than 10%, and the MAPE value of matric suction was 17.3% and in the range of 10-20%. Thus, the established formulas have good forecasting accuracy and may be applied to the stability analysis of the unsaturated soil slope. However, further study is warranted for validation.

• 한국건축시공학회지
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• 제10권3호
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• pp.91-97
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• 2010

현재 건물 부력에 대한 보호조치로 경제성 및 효율성 측면을 고려하여 영구배수 공법의 사용이 증가하고 있다. 영구배수공법은 건축물에 접하는 지하수를 외부로 배수시켜 건축물에 작용하는 부력을 근본적으로 제거하는 공법으로, 영구배수공법 사용시 유출지하수가 발생하게 된다. 또한 우리나라는 국제인구행동연구소(PAI)에서 지정한 물 부족 국가로 지정되어 유출지하수의 활용이 요구되고 있지만 이에 대한 평가프로세스가 아직 충분하지 않다. 따라서 본 연구는 현장 적용 사례를 통해 현장 단위에서 유출되는 지하수의 활용여부를 결정할 수 있는 평가 프로세스를 구축하고 경제성을 분석하였다. 그 결과 상수도와 비교한 10년간 상수절감 비용을 통해 유출지하수의 활용이 가능한 것으로 나타났다.