• Geomechanics and Engineering
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• v.8 no.2
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• pp.187-220
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• 2015

Soil disturbance induced by installation of mandrel driven vertical drains decreases the in situ horizontal hydraulic conductivity of the soil in the vicinity of the drains, decelerating the consolidation rate. According to available literature, several different profiles for the hydraulic conductivity variation with the radial distance from the vertical drain, influencing the excess pore water pressure dissipation rate, have been identified. In addition, it is well known that the visco-plastic properties of the soil also influence the excess pore water pressure dissipation rate and consequently the settlement rate. In this study, a numerical solution adopting an elastic visco-plastic model with nonlinear creep function incorporated in the consolidation equations has been developed to investigate the effects of disturbed zone properties on the time dependent behaviour of soft soil deposits improved with vertical drains and preloading. The employed elastic visco-plastic model is based on the framework of the modified Cam-Clay model capturing soil creep during excess pore water pressure dissipation. Besides, nonlinear variations of creep coefficient with stress and time and permeability variations during the consolidation process are considered. The predicted results have been compared with V$\ddot{a}$sby test fill measurements. According to the results, different variations of the hydraulic conductivity profile in the disturbed zone result in varying excess pore water pressure dissipation rate and consequently varying the effective vertical stresses in the soil profile. Thus, the creep coefficient and the creep strain limit are notably influenced resulting in significant changes in the predicted settlement rate.

• Geomechanics and Engineering
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• v.8 no.4
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• pp.523-540
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• 2015

Based on limit equilibrium principles, this study presents a theoretical derivation of a new analytical formulation for estimating magnitude and lateral earth pressure distribution on a retaining wall subjected to seismic loads. The proposed solution accounts for failure wedge inclination, unit weight and friction angle of backfill soil, wall roughness, and horizontal and vertical seismic ground accelerations. The current analysis predicts a nonlinear lateral earth pressure variation along the wall with and without seismic loads. A parametric study is conducted to examine the influence of various parameters on lateral earth pressure distribution. Findings reveal that lateral earth pressure increases with the increase of horizontal ground acceleration while it decreases with the increase of vertical ground acceleration. Compared to classical theory, the position of resultant lateral earth force is located at a higher distance from wall base which in turn has a direct impact on wall stability and economy. A numerical example is presented to illustrate the computations of lateral earth pressure distribution based on the suggested analytical method.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.14 no.5
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• pp.391-397
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• 2002

Pressure drop were experimentally investigated for ice slurry flowing in the acrylic pipes with inner diameter of 24 mm. Ice slurry was made from 6.5% ethylene glycol-water solution, and the pipes is consisted of horizontal, vertical (upward and downward) and $90^{\circ}$ elbow pipe. The ice Packing factor (IPF) and the flow rate of the experiments were varied from 0 to 30% and from 5 to 70kg/min respectively The measured pressure drop in various pipe positions were compared with those for the solution flow (IPF=0). The pressure drop was larder than that for solution flows as the IPF increased when the flow rate was low or very high. Sharp increases in pressure drop were observed for the cases when IPF is more than 70% in horizontal and vertical pipes, whereas the pressure drop increased with the IPF simultaneously in an elbow pipe.

• Journal of the Korean Geotechnical Society
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• v.33 no.11
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• pp.59-72
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• 2017

In this study, the calculation method of the active earth pressure acting on the imaginary vertical plane at the end of the heel of the wall is proposed. For cantilever retaining wall, a change of shear zone behind the wall affects the earth pressure in the vertical plane at the end of heel of the wall depending on wall friction and angle of ground slope. It is very complicated to calculate the earth pressure by a limit equilibrium method (LEM) which considers angles of failure planes varying according to the heel length of the wall. So, the limit analysis method (LAM) is used for calculation of earth pressure in this study. Using the LAM, the earth pressures considering the actual slope angles of failure plane are calculated accurately, and then horizontal and vertical earth pressures are obtained from them respectively. This study results show that by decreasing the relative length of the heel, the slope angle of inward failure plane becomes larger than theoretical slope angle but the slope angle of outward failure plane does not change. And also the friction angle on the vertical plane at the end of the heel of the wall is between the ground slope angle and the wall friction angle, thereafter the active earth pressure decreases. Finally, the Coulomb earth pressure can be easily calculated from the relationship between friction angle (the ratio of vertical earth pressure to horizontal earth pressure) and relative length of the heel (the ratio of heel length to wall height).

• Korean Journal of Applied Biomechanics
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• v.19 no.4
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• pp.771-778
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• 2009

We aimed to determine the effect of heel height on foot pressure by comparing and analyzing data on foot pressure in shoes with different heel heights. Qn the basis of a previous study, we selected 3cm and 7cm as the shoe heel heights preferred by female college students. We divided 10 female students into forefoot and hindfoot to measure vertical force, maximum pressure, and average pressure. The average pressure on the forefoot was higher and that on the hindfoot was lower in the case of 7cm high-heeled shoes. The maximum pressure on the forefoot was significantly higher in the case of the 7cm heel height (p<.05). The vertical force, maximum pressure, and average pressure on the hindfoot were also significantly higher in the case of the 7cm heel height (p<.05). The results showed that wearing 7cm high-heeled shoes exerted greater maximum pressure on the forefoot and greater vertical force, maximum pressure, and average pressure on the Hndfoot. This leads to increase in confining pressure caused by high pressure distribution over the forefoot and increase in the pressure on the hindfoot, which may cause deformation of toes and heel pain over a long period. Therefore, female college students who wish to wear high heels are recommended to wear 3cm high-heeled shoes rather than 7cm high-heeled shoes.

• Journal of Korean Tunnelling and Underground Space Association
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• v.15 no.6
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• pp.559-570
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• 2013

High speed railway can transport large quantity of people and commodities in a short time and has become one of the most desirable and environmentally friendly transportation. However, it is hard to have a complicated route for high speed railways, construction of tunnels is essential to pass through a mountain area. When a high speed train enters a tunnel, pressure wave is created in a tunnel and the wave causes micro pressure wave and discomfort to passengers. In order to alleviate pressure wave in a tunnel, constructing a vertical shaft is one of the most efficient ways. This study represents a numerical analysis module, which takes into account the effect of a vertical shaft in a tunnel. The module can be used in a numerical program (TTMA) specialized for aerodynamics in a tunnel, and it was validated by comparing numerical results with various measurements in Emmequerung tunnel and results from numerical analysis using Fluent.

• Proceedings of the SAREK Conference
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• 2008.06a
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• pp.895-900
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• 2008

It is the objective of the present study to conduct correlation analysis for deriving control parameters in vertical shafts using the results obtain by the design of experiments in the preceding research. The control parameters are categorized into objective parameters, derived parameters, condition parameters, operation parameters, and sensing parameters. The maximum pressure in the shaft should be sufficiently small in order to maintain exhaust hood performance. The pressure variations between floors should also be minimized in order to maintain uniform exhaust performance between floors and to save energy for excessive pressure drop in the shaft. The standard deviation based on -4Pa is proposed as an objective parameter to control pressure in shafts. The correlation equation has been obtained between the standard deviation and the sensing parameters of outdoor temperature and the pressure at the top of the shaft.

• Journal of Ocean Engineering and Technology
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• v.15 no.4
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• pp.20-27
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• 2001

Recently numerical approaches for wave loads acting on the vertical caisson of breakwater, and resulting wave reflection and transmission coefficients have been performed. Although the numerical studies by Sulisz's(1997) and Kim et al.(2000) are suggested representatively, theoretical formulation for nonlinear wave pressure is not developed yet. And experimental results of Sulisz(1997) revealed that nonlinear uplift pressure on the caisson may be produced largely on the case of caisson founded on the high rubble mound. From the results of this study, the nonlinear theory for the uplift wave pressure acting on the caisson by applying boundary integral method of Green theorem is formulated, and also the characteristics of nonlinear uplift pressure and run-up height on the caisson are evaluated numerically, according to the variations of hydraulic properties of the rubble mound.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.15 no.2
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• pp.109-115
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• 2003

The performance of two vertical-blade eliminators (V1, V2) and two horizontal-blade ones (H1, H2) for absorption chillers were tested in terms of pressure drop and refrigerant entrainment. The test was carried out using a wind tunnel with a cross section of 300 mm$\times$300 mm. The pressure drop of four eliminators tested was found to be in the rage of 1.0~2.7mm $H_2O$ at the face velocity of 2m/s. In the refrigerant entrainment test the vertical-blade eliminators showed much better performance than the horizontal-blade ones. The horizontal-blade eliminators showed satisfactory results at the air velocity of 2m/s but exceeded the limit value at 3 m/s. Since the cooling capacity of a machine is lowered by about 2.5% at the pressure drop of 1 m $H_2O$, more researches are required to reduce the pressure drop in the eliminator.

• Journal of Industrial Technology
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• v.8
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• pp.3-11
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• 1988

Shock pressure of wave breaking on vertical wall is studied experimentally with beaches, which have four different slopes (1/4.02, 1/7.05, 1/10, 1 /13.5). This results is summerized as follows: 1. Maximum impact presures are occured where the wave break directly on the wall rather than breaking in front of the wall. 2. Deep water steepness, and the beach slope are the two Quantities governing the magnitude and location of maximum dimensionless impact pressure from wave breaking directly on the wall, also, the greatest pressure is produced with a beach slope of 1/10. 3. This study is clearly shown that the location of maximum pressure can be presented above still water level under respectively experimental condition. The dimensionless elevation of maximum Pressure is greatest on a beach slope of 1/10.