• Proceedings of the Korean Geotechical Society Conference
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• 2008.10a
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• pp.591-604
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• 2008

In this study, two design examples of drilled shafts on soft ground in Ho-Chi-Minh City, Vietnam are introduced. One is for a 27-story apartment and the other is for a Arch bridge over Saigon river. Unlikely the normal cases in Korea, all of the bored pile foundations are supposed to be placed on soil layers. Therefore, skin friction between pile and ground is the most crucial design parameter. Three methods using SPT N value of sandy soil -Korean Road Bridge Code(1996), Reese and Wright (1977), and O'Neill and Reese (1988)- were adopted to obtain an ultimate axial bearing capacity. In order to verify the calculated bearing capacity, 3 sets of static load test and a Osterberg Cell test were performed at an apartment site and a bridge site respectively. LRFD (Load Resistance Factored Design) method was compared with ASD (Allowable Stress Design) method. On application of ASD method, safety factor for skin friction was adopted as 2 or 3 while safety factor for end bearing was 3. The design bearing capacities from ASD method matched well with those from LRFD method when safety factor for skin friction was adopted as 2.

• Journal of the Korean Geotechnical Society
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• v.18 no.4
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• pp.189-197
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• 2002

The bearing capacity of open-ended piles is affected by the degree of soil plugging, which is quantified by the incremental filling ratio, IFR. There is not at present a design criterion for open-ended piles that explicitly considers the effect of IFR on pile load capacity. In order to investigate this effect, model pile load tests using a calibration chamber were conducted on instrumented open-ended piles. The results of these tests show that the IFR can be estimated from the plug length ratio PLR, which is defined as the ratio of soil plug length to pile penetration depth. The unit base and shaft resistances decrease with increasing IFR. Based on the results of the model pile tests, new design equations for calculating base load capacity and shaft load capacity of open-ended piles are proposed.

• Tribology and Lubricants
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• v.17 no.4
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• pp.321-334
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• 2001

The influence of aerated oil on high-speed journal bearing Is examined by thermohydrodynamic lubrication theory to lubrication with mixtures of a Newtonian liquid and an ideal gas. For this purpose, analytical models for viscosity and density of aerated oil in fluid-film bearing are applied. Convection to the walls, mixing with supply oil and re-circulating oil, and some degree of journal misalignment are considered. The results show that deliberate oil aeration can increase the load capacity of high-speed plain Journal bearing. And the load capacity is increased more by oil aeration under the conditions of shaft misalignment and higher speed.

• Proceedings of the Korean Geotechical Society Conference
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• 2002.11a
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• pp.209-236
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• 2002

Ultimate pile capacity - Point resistance - Frictional resistance - Determination of point and frictional resistances from field tests - Summary of recommendations from design Group effects Settlement analysis.

• Journal of the Korean Geosynthetics Society
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• v.22 no.1
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• pp.39-51
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• 2023

The bearing capacity of the prebored pile has been studied by many researchers. However, The bearing capacity of the prebored pile has been studied by many researchers. However, comparative studies between design data and pile load test data on the load sharing ratio and the settlement were insignificant. Therefore, the design data and the static load test results were compared for the prebored open-end steel piles. In the compressive static pile load test, the load sharing ratios of the base resistance and the shaft resistance were 13%~40% and 60%~87%, respectively and the settlements were measured 2.2mm~4.7mm. In the current bearing capacity calculation formula, the base resistance was shared between 54% and 75%, and the shaft resistance was shared between 25% and 46% and the settlements were calculated about 19.8mm~23.6mm. The settlement in the current bearing capacity calculation formula was 321% to 776% (average : 445%) larger than the settlement in the result of load test. When the settlement were calculated using the load sharing ratio in the pile load tests, it was 137% to 525% larger than the test settlement, and it was as large as 204% on average. It was confirmed that an appropriate evaluation of the load sharing ratio had an important effect on the calculation of pile settlement.

• Proceedings of the KSME Conference
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• 2001.06c
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• pp.305-310
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• 2001

Within some degree of journal misalignment, maximum pressure, maximum temperature, bearing load, friction and side leakage in high-speed journal bearing operation are examined under the condition of variable density and specific heat. The results are compared with the calculation results under the conditions of constant density and specific heat, and variable density and constant specific heat. It is found that the effects of variable density and specific heat on shaft misalignment are significant in determining the load capacity of a journal bearing operating at high speed.

• Journal of Korean Tunnelling and Underground Space Association
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• v.21 no.3
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• pp.363-375
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• 2019

Since the double-deck tunnel is deeply constructed in the city, it is necessary to secure the installation space of air supply and exhaust, escape passage stairs, elevator, distribution facilities and connection tunnels in the vertical shaft for the double-deck tunnel. Also, in order to minimize the effect of construction on adjacent area, it is necessary to construct the concrete structures at high speed in vertical shaft after tunnel excavation. Therefore, the slabs and the stairs in vertical shaft are needed to be constructed using precast concrete, and the rapid construction techniques of bracket for supporting the inner precast structure are needed. The bracket installation methods include cast-in-place concrete, precast concrete and steel. In this study, the improvement of the steel brackets with good economical efficiency and good workability was carried out in consideration of the improvement of the construction speed. We have developed a new bracket that is optimized through bracket shape improvement, anchor bolt position adjustment and quantity optimization. As a result of the structural performance test, it was confirmed that the required load supporting capacity was secured. As a result of structural performance test for bar type anchor bolt and bent anchor anchor bolt, it was confirmed that the required load carrying capacity was secured and that the load bearing capacity of bent anchor bolt was large.

• Journal of the Korean Geotechnical Society
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• v.24 no.6
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• pp.85-93
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• 2008

For long piles driven in deep clay deposits, it is difficult to estimate the ultimate bearing capacity due to large resistance induced by long embedded depth, and also the load transfer curve due to large residual load induced by negative skin friction, even with the performance of pile load tests. In this research, a hi-directional load test on a PHC pile driven in deep soft deposit was performed in order to evaluate the tip and shaft resistances separately, which are feasible to estimate the ultimate bearing capacity of the pile. Residual load of the pile was determined by continuous monitoring of pile strains after the pile installation. The true resistance and true load-movement curve of the pile were properly estimated by taking account of the residual load. A model far behavior of the shaft resistance vs. movement was also proposed, which includes the effects of residual load based on the experiment. Consequently, it was proved that the residual load should be taken into consideration for correctly analyzing load test results of piles in deep clay deposits.

• Proceedings of the Korean Geotechical Society Conference
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• 2001.03a
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• pp.371-378
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• 2001

The working load at pile is sometimes subjected to not only compression load but also lateral load and uplift forces. Pile foundation is essential and uplift load can be applied because of buoyancy, a typhoon, wind or seismic forces. This study was carried out to determine the uplift capacity of concrete pile foundation driven in clay. Pile was driven in clay, between pile and clay adhesion factor was estimated, and it is the mean value between the cast-in-situ-pile and steel pipe pile. When pile foundation is loaded for long time, creep behavior occurs. The behavior of creep is originated from the clay creep contacted with pile. The creep behavior of pile foundation embedded in clay is heavily depended on the thickness of clay around the pile shaft, pore water pressure in clay, and creep behavior of clay.

• Proceedings of the Korean Geotechical Society Conference
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• 2006.10a
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• pp.585-592
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• 2006

Recently, many high rise buildings is planning and under construction over the world. The drilled shafts as a foundation of high rise buildings are often adopted fur the purpose of construction safety and construction cost effectiveness. It is common that the capacity of drilled shafts is beyond conventional conception. The reasonable design and quality assurance for the drilled shaft as foundation of high rise building become much more important since the drilled shafts should bear much higher working load. This paper reviews state of the art of the design and quality assurance for the drilled shafts as foundation of high rise buildings. And also some related suggestions are given in this paper.