• Geomechanics and Engineering
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• 제22권5호
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• pp.375-384
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• 2020

In this study, the application of conventional cubic law to a deep depth condition was experimentally evaluated. Moreover, a modified equation for estimating the rock permeability at a deep depth was suggested using precise hydraulic tests and an effect analysis according to the vertical stress, pore water pressure and fracture roughness. The experimental apparatus which enabled the generation of high pore water pressure (< 10 MPa) and vertical stress (< 20 MPa) was manufactured, and the surface roughness of a cylindrical rock sample was quantitatively analyzed by means of 3D (three-dimensional) laser scanning. Experimental data of the injected pore water pressure and outflow rate obtained through the hydraulic test were applied to the cubic law equation, which was used to estimate the permeability of rock fracture. The rock permeability was estimated under various pressure (vertical stress and pore water pressure) and geometry (roughness) conditions. Finally, an empirical formula was proposed by considering nonlinear flow behavior; the formula can be applied to evaluations of changes of rock permeability levels in deep underground facility such as nuclear waste disposal repository with high vertical stress and pore water pressure levels.

• Journal of Biosystems Engineering
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• 제19권1호
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• pp.3-8
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• 1994

An experiment on the expression and dewatering of chinese cabbage was conducted in order to investigate its dewatering behavior. Chopped cabbage was packed into cylinder and pressed by piston upto the predetermined pressure on Instron-1000. The rates of dewatering were affected domintantly by the applied pressure, but not significantly by the packed amount of cabbage in the cylinder. The pressure effect was increased very abruptly at first, but the increase rate was very low at high pressure greater than 20 MPa, showing great deviation from linear dependence of flow rate on pressure in Darcy's Law. Therefore, water expression from cabbage was not Newtonian flow of water through cell wall. In fact, the squeezed water contained a lot of solid particles, about 3% of solid cabbage particles, showing destruction of cell wall. It appeared that compression and dewatering of vegetable wastes in the low pressure. under 20 MPa, is more desirable for later treatment of the dewater. More researches are needed in order to develop a treatment method for the solid particles in the expressed water before an expeller treatment system can be applied to vegetable wastes.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2000년도 가을 학술발표회 논문집
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• pp.201-208
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• 2000

In this study, the behavior of saturated sandy soils under dynamic loads - pore water pressure and effective stress - was investigated using Disturbed State Concept(DSC) model. The model parameters are evaluated from laboratory test data. During the process of loading and reverse loading, DSC model is utilized to trace strain-hardening and cyclic softening behavior. The procedure of back prediction proposed in this study are verified by comparing with laboratory test results. From the back prediction of pore water pressure and effective mean pressure under cyclic loading, excess pore water pressure increases up to initial effective confining pressure and effective mean pressure decrease close to zero in good greement with laboratory test results. Those results represent the liquefaction of saturated sandy soils under dynamic loads. The number of cycles at initial liquefaction using the model prediction is in good agreement with laboratory test results. Therefore, the results of this study state that the liquefaction of saturated sandy soils can be explained by the effective tress analysis.

• 한국해양공학회지
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• 제23권1호
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• pp.60-66
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• 2009

This study presents an experimental investigation of the shallow water impact of a box type structure. The analysis was done based on the video images captured by a high speed camera, the flow field obtained by PIV (Particle Image Velocimetry), and pressure measurements in the divided region. The video images showed quite good agreement with the description given by Korobkin. The PIV measurements of the velocity field provided a clear view of the flow pattern for all three stages. The pressure was measured at the bottom of the tank with strain gauge type pressure gauges. The pressure measurements showed the characteristics of divided regions.

• 한국지반공학회지:지반
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• 제8권2호
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• pp.59-70
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• 1992

지질구조의 일례를 모형화하여 3종류 시료에 대해 간극수압계를 사용하여, 가압수두와 간극비 변화에 따른 간극수압 변화측정을 60회의 실험을 통하여 실시하였다. 본 연구는 불포화 붕적토층에서 간극비와 가압수두 변화에 따른 간극수압의 변화를 기록하여 최종간극수압 VWT와 공기간극수압 Ua를 구하여 이들의 변화를 최종반응률과 공기반응률로 나타냈으며, 시료별로 투수계수와 간극비의 관계를 수식화 하였다. 실험결과 시료에 따라 간극수압 변화 형태가 계단형과 파형으로 나타났으며, 최종간극수압까지의 시간 지체는 모래, 사질실트, 점토질 모래 순이었다.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2012년도 제38회 춘계학술대회논문집
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• pp.157-162
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• 2012

미크론 크기의 알루미늄 분말과 물 혼합물의 기초 연소 특성 연구를 진행하였다. 대기압 환경에서 연소속도에 영향을 미치는 당량비와 혼합물 밀도를 변화시켜 알루미늄-물 혼합물의 연소 특성 연구를 진행하였다. 이를 바탕으로 고압 환경하에서의 알루미늄 분말과 물 혼합물에 대한 연소 특성을 연구하기 위한 장치를 설계하였다. 고압 환경에서 2~50기압 범위에서는 압력에 따른 연소속도의 영향은 나노 분말의 연소 특성과 동일하였으나, 50~70기압 범위에서는 급격한 연소속도 증가 현상이 관찰되었다. 당량비에 따른 실험에서는 산화제 과잉(eq=1.5) 조건에서는 50기압 이상에서는 연소가 진행되지 않았다.

• 한국안전학회지
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• 제24권5호
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• pp.21-27
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• 2009

Effective way of cooking oil fire extinguishment is using water mist system which has cooling and smothering effects. Low pressure water mist system has advantage because it is compatible with existing sprinkler systems. To increase the effectiveness of low pressure water mist system, additives can be used which increase the momentum of water particle and the chemical effect. In this experiment, aqueous film forming form(AFFF) agent is used as additive and the effect of additive concentration and water pressure are experimented. For the extinguishment of cooking oil fire such as soybean and olive oils, AFFF agent is effective and can decrease the fire extinguishing time and water consumption.

• 설비공학논문집
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• 제14권4호
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• pp.269-277
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• 2002

Dynamic characteristics of water hammer arresters installed in a building water supply system have been investigated numerically by utilizing a commercial rode that employs the method of characteristics. Some preliminary results with those arresters produced in this study agree well with the previously reported. Then, the arresters have been incorporated into a water supply pipe system of a $59m^2$ apartment unit constructed by a leading construction company, and their dynamic characteristics, especially on the reduction in the water hammer pressure, are investigated. It is found that the setting of the arresters in the pipe system, which is recommended by the company, may not be proper for reducing the pressure to less than 1082.0 kPa when buick-closure valves in the pipe system are closed within 30 ms at the static pressure of 542.6 kPa. More arresters in the system may be required to meet a pressure criteria.

• 상하수도학회지
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• 제29권6호
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• pp.617-623
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• 2015

In this study, determination methods of monitoring location in water distribution system were suggested and applied to real test bed. Small block of Gwangtan water distribution system is consisted of 582 pipes, 564 junctions, 1 reservoir, and 1 pump station. Small block of Ho Chi Minh water distribution system is consisted of 162 pipes, 148 junctions, and 1 reservoir. Two small block water distribution systems were analyzed by pressure contribution analysis method to determine the optimum monitoring locations. The pressure change was estimated at each junctions by the additional demand at a junction. From the results, the optimum monitoring location can be determined by rank of pressure contribution index at each junctions due to demand change at a junction.

• Geomechanics and Engineering
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• 제12권4호
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• pp.707-721
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• 2017

The objective of this paper is to experimentally study the consolidation of saturated silty clay subjected to repeated heating-cooling cycles using a modified temperature-controlled triaxial apparatus. Focus is placed on the influence of the water content, confining pressure, and magnitudes and number of thermal loading cycles. The experimental results show that the thermally induced pore pressure increases with increasing water content and magnitude of thermal loading in undrained conditions. After isothermal consolidation at an elevated temperature, the pore pressure continues to decrease and gradually falls below zero during undrained cooling, and the maximum negative pore pressure increases as the water content decreases or the magnitude of thermal loading increases. During isothermal consolidation at ambient temperature after one heating-cooling cycle, the pore pressure begins to rise due to water absorption and finally stabilizes at approximately zero. As the number of thermal loading cycles increases, the thermally induced pore pressure shows a degrading trend, which seems to be more apparent under a higher confining pressure. Overall, the specimens tested show an obvious volume reduction at the completion of a series of heating-cooling cycles, indicating a notable irreversible thermal consolidation deformation.