• Proceedings of the Earthquake Engineering Society of Korea Conference
• /
• 1998.04a
• /
• pp.81-88
• /
• 1998

During an earthquake, there are three main components of excitation : horizontal excitation of the ground, vertical excitation of the pile due to superstructure feedback produced by vertical excitation of the ground, and the seawater excitation induced by the vertical ground shaking, that is, "the seaquake." These excitations could have effects on the soil plugs in open-ended pipe piles installed at offshore sites. In this study, seaquake excitation induced by the vertical ground shaking was simulated by pulsing the water pressure at the seabed. During a seaquake, due to induced excess porewater pressure and pressure gradients in the soil, the capacity of open-ended pipe piles installed in a simulated sea depth of greater than 220 m was reduced serevely and the soil plugging resistance was degraded by more than 80%. The soil plug was failed because of the upward seepage forces that developed in the soil plug due to excess pore water pressure produced in the bottom of the soil plug during the seaquake. The compressive capacity of an open-ended pile in a simulated sea depth of less than 220m was reduced only by about 10%, and the soil plug resistance was degraded by less than 5%.s than 5%.

• Journal of The Korean Society of Agricultural Engineers
• /
• v.54 no.5
• /
• pp.103-111
• /
• 2012

In this study, the full-scale laboratory model test on utilization of recycled aggregates and crushed stone as vertical drains to use an alternative material of sand in soft ground is performed. The settlement and pore water pressure were measured to evaluate the discharge capacity and filed application, and the results were compared and analyzed through the finite element method. The measured and estimated settlement in all vertical drain materials decreases gradually with the load increase. The measured settlement 6.55~8.63 mm, and the estimated by the Hyperbolic model was 7.45~7.92 mm. So the model used for the analysis can be applied to the settlement estimation of the actual field. The variations of pore water pressure with time showed constantly regardless of the load in all vertical drainage materials. The pore water pressure was similarity to that of sand after rapid drawdown. Therefore, it was applicable to the field because discharge capacity was enough to be an alternative material to the sand which had been being used as the vertical drains.

• Korean Journal of Agricultural Science
• /
• v.37 no.1
• /
• pp.97-104
• /
• 2010

In this study, a laboratory model test on utilization of recycled aggregates and crushed stone as vertical drains to use alternative material of sand in soft ground is performed. The vertical and horizontal coefficient of permeability of the recycled aggregates and crushed stone showed largely 1.2~4.0 times and 3.0~3.3 times greater than sand, respectively. Therefore, it showed enough to be an alternative material to the sand which had been being used as the vertical and horizontal drainage material before. The variations of pore water pressure with time showed constantly regardless of the load in all vertical drainage materials. When water level drops suddenly, the pore water pressure of the recycled aggregate and crushed aggregate is reduced to nearly zero. Therefore, it was applicable to the field because discharge capacity was similarity to that of sand. The settlement in crushed aggregates and recycled aggregate decreases gradually with the load increase. When water level drops suddenly, earth pressure in all drains materials was evaluated the equivalent drainage capacity similarity to sand because it show approaching the nearly zero.

• Journal of the Earthquake Engineering Society of Korea
• /
• v.18 no.6
• /
• pp.279-289
• /
• 2014

Considering a rigorously fluid-structure interaction, a method for an earthquake response analysis of a floating offshore structure subjected to vertical ground motion from a seaquake is developed. Mass, damping, stiffness, and hydrostatic stiffness matrices of the floating offshore structure are obtained from a finite-element model. The sea water is assumed to be a compressible, nonviscous, ideal fluid. Hydrodynamic pressure, which is applied to the structure, from the sea water is assessed using its finite elements and transmitting boundary. Considering the fluid-structure interaction, added mass and force from the hydrodynamic pressure is obtained, which will be combined with the numerical model for the structure. Hydrodynamic pressure in a free field subjected to vertical ground motion and due to harmonic vibration of a floating massless rigid circular plate are calculated and compared with analytical solutions for verification. Using the developed method, the earthquake responses of a floating offshore structure subjected to a vertical ground motion from the seaquake is obtained. It is concluded that the earthquake responses of a floating offshore structure to vertical ground motion is severely influenced by the compressibility of sea water.

• Proceedings of the Korean Geotechical Society Conference
• /
• 2006.03a
• /
• pp.1165-1172
• /
• 2006

In this study, an aspect of settlement, developed from different ground improvement method like suction drain method using vacuum pressure and vertical drain method using overburden pressure, was compared each other. In order to analyze settlement tendency of each method exactly, the finite element analysis program was used. The analyses of vertical settlement and lateral displacement for suction drain method and vertical drain method were conducted independently during the solving stage. The initial condition of drainage zone was fixed with 25m depth and 21m width. After the program analyses, the settlement condition had a different tendency with the ground improvement method. Especially, in the results of vertical drain method, the disparity of settlement between the middle of improved zone and unimproved zone. In the case of suction drain method, however, the difference of settlement was smaller than that of vertical drain method.

• Journal of the Korean Society for Aviation and Aeronautics
• /
• v.26 no.2
• /
• pp.83-90
• /
• 2018

This paper describes a case study on the design factor analysis of vertical wind tunnel for skydiver's training or experiencing of paradropping exercise in the air. The case study of vertical wind tunnel design is to provide the knowledges on effects of parameter's variation when it is applied to overall or partial duct of tunnel circuit. The analysis of design parameters based on pressure loss are produced one by one through the tunnel components from the flight chamber because the wind tunnel must satisfy the requirement of flight chamber such as flow speed, quality and quantity. Results shows the various effects of parameter variation with pressure loss in the wind tunnel circuit. Pressure loss should be based on the determination of fan and power system which can be selected from market or new design.

• Nuclear Engineering and Technology
• /
• v.36 no.1
• /
• pp.12-23
• /
• 2004

In the present study a new measurement technique has been developed, which uses an ultrasonic transmission signal in order to identify the vertical two phase flow pattern. The ultrasonic measurement system developed in the present study not only provides the information required for the identification of vertical two phase flow patterns but also makes real time identification possible. Various vertical two phase flow patterns such as bubbly, slug, churn, annular flow etc. have been accurately identified with the present ultrasonic measurement system under atmospheric condition. In addition, the present test apparatus can practically simulate the ultrasonic propagation characteristics under high temperature and high pressure systems. Therefore, it is expected that the present ultrasonic flow pattern identification technique could be applicable to the vertical two phase flow systems under high temperature and high pressure conditions.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.8 no.4
• /
• pp.550-560
• /
• 1996

Recently, fluidized bed heat exchangers with circulating liquid are widely used in a number of places-chemical, process, food concentration, waste water treatment facilities, etc. In a circulating heat exchanger, solid particles circulate with the liquid, thereby increase the heat transfer and reduce the fouling potential of the heat exchanger. In this study, glass beads were circulated through a vertical tube. The pressure loss and the heat transfer coefficient were measured. At low flow velocities, glass beads enhanced the heat transfer considerably. The enhancement increased as the volume fraction of the glass beads increased. The pressure loss showed a similar trend. From the observed particle behavior near tube wall, a possible explanation of the trend is provided.

• Proceedings of the Korea Society for Energy Engineering kosee Conference
• /
• 1996.04a
• /
• pp.121-131
• /
• 1996

Recently, circulating liquid fluidized bed heat exchangers are widely used in a number of places - chemical, process, food concentration, waste water treatment facilities, etc. In a circulating heat exchanger, solid particles circulate with the liquid, thereby increase the heat transfer and reduce the fouling potential of the heat exchanger. In this study, glass beads were circulated through a vertical tube. The pressure loss and the heat transfer coefficient were measured. At low flow velocities, glass beads enhanced the heat transfer considerably. The enhancement increased as the volume fraction of the glass beads increased. It also increased as the particle diameter increased. The pressure loss showed a similar trend. From the observed particle behavior near tube wall, a possible explanation of the trend is provided.

• Journal of the Korean Geotechnical Society
• /
• v.26 no.12
• /
• pp.51-60
• /
• 2010

Earth pressure due to gravity generally increases linearly with the depth, but the distribution of earth pressure due to surface load depends on the loading condition, the ground condition, and the boundary condition. In this study, the earth pressure on a rigid wall due to the vertical surface load was measured in experiments. Rigid wall was built in the model test box, and it was filled with homogeneous sandy ground (width 30 cm, height 88 cm, length 110 cm). Rigid wall was composed of 8 segments, which were tested on the two load cells. In the tests, we observed the distribution of the earth pressure on the rigid wall depending on the vertical surface load and it's location. According to the test results, the lateral earth pressure due to the vertical surface load showed its maximum value at a constant depth and decreased with the depth, to the negligible value at the critical depth. The critical depth and the depth at which lateral earth pressure reaches its maximum were not decided by the magnitude of the vertical surface load. They were dependant on the distance from the rigid wall.