• Proceedings of the Korean Geotechical Society Conference
• /
• 2005.10a
• /
• pp.521-527
• /
• 2005

In the past decades, complain about ground vibration and noise induced by pile driving has been quickly increased. Because of that, auger drilled piling methods have frequently used specially in urban area. However, the present auger drilled piling methods induce inevitable ground disturbance as well as a certain degree of vibration and noise due to the final hammering. For these reasons, a new auger drilled piling method is required to be developed. This paper introduces PDT(Pulse Discharge Technology) piling method and presents the characteristics of bearing capacity. The PDT piling method is to install in-situ piles using electric power so called Pulse. The pile installed by PDT appears to be able to develop shaft and end bearing capacity efficiently.

• Proceedings of the Korean Geotechical Society Conference
• /
• 2010.03a
• /
• pp.1088-1093
• /
• 2010

The Smart bi-directional pile load test with variable end plate overcomes the shortcoming of the Osterberg cell test. It is possible that the ultimate bearing capacity of piles can be known by using two different end plates. The first step is to measure end bearing capacity with smaller end plate and the second step is similar to the conventional O-cell test. In this study, model test was performed to evaluate the smart bi-directional pile load test in sand. Vertical displacement of the model pile were messured at the axial loading condition.

• Proceedings of the Korean Geotechical Society Conference
• /
• 2004.03b
• /
• pp.544-551
• /
• 2004

Piles are structural elements made of steel, concrete or timber, and utilize as pile foundation which is one of deep foundations. Driven pile among them, which drives pile into the ground, is fast-constructable, less expensive and it supplies much bearing capacity. For these reasons, its demand is steady. In this study, by selecting the cases which reached ultimate failure during in-situ static loading tests, bearing capacities acquired from these tests were compared with those computed by existing theories and formula. As the results of the analysis, ultimate bearing capacity computed by theoretic formula were less or similar to those of test results in most cases, but lower ground water level and more dense layer where end of piles were reached remarkably high bearing capacity in theoretical methods. ${\beta}-method$ and Korean structure foundation design standard were sensitive to ground physical properties. Meyerhof metbod and API code were relatively independent from site condition.

• Proceedings of the Korean Geotechical Society Conference
• /
• 2010.09a
• /
• pp.303-314
• /
• 2010

This study, as basic research which was intended to develope the surface reinforcement method using reinforcement material which is applicable to very soft ground in Korea, was aimed at proposing the design parameter for the surface ground improvement method. To that end, a wide width tensile test using geotextile, geogrid and steel bar (substitute for bamboo) and 49 kinds of the laboratory model tests were conducted. And the result the study suggested $\beta_s$, the stiffness coefficient to evaluate the stiffness effect of reinforcement materials. Then, it was also found that the stiffness coefficient, $\beta_s$ as the testing constant would be appropriate as high as 1.0, 1.1 and 1.5 for geotextile, geogrid and steel bar, respectively. And It was evaluated that the stiffness effect affecting reinforcement improvement effect would be reduced as the thickness of embeded depth increases and that RFe, the stiffness effect reduction coefficient would have positive correlation with H/B. Finally, it was confirmed that the bearing capacity gained from the method to calculate bearing capacity, which was suggested in the study, would almost correctly estimate the capacity, demonstrating the appropriateness of the proposed bearing capacity calculation method.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
• /
• 2002.10b
• /
• pp.425-426
• /
• 2002

Lineal and angular movements of many engine components make the lubricant absorb air and the aerated lubricant greatly influences the clearance performance of contacting behaviors of engine components such as big-end bearing, cam and tappet, etc. This study investigates the behaviors of aerated lubricant in the gap between con-rod bearing and proceeding which is one of the most frictional energy consuming components in the engine. Our assumption for the analysis of aerated lubricant film is that the film formation is influenced by the two major factors. One is the density characteristics of the lubricant due to the volume change of lubricant by absorbing the bubbles and the other is the viscosity characteristics of the lubricant due to the surface tension of the bubble in the lubricant. In our investigation, it is found that these two major factors surprisingly increase the load capacity in certain ranges of bubble sizes and densities. Frictional forces are also influenced by the aerated bubble size and density, which eventually enlarge the shear resistance due the surface tension, Modified Reynolds' equation is developed for the computation of fluid film pressure with the effects of aeration ratio under the dynamic loading condition. From the calculated load capacity by solving modified Reynolds' equation, proceeding locus is computed with Mobility method at each time step.

• Journal of the Korean Geotechnical Society
• /
• v.19 no.2
• /
• pp.237-246
• /
• 2003

The driven pile has environmental problems such as vibration and noise. Especially, if the site consists of gravel, cobble and weather rock, the driven pile can not be applied. Therefore, the application of the drilled shafts is increasing in Korea. However, the bearing capacity values by the suggested theoretical formulas are generally considered too conservative. In this paper, static load tests for the rock socketed drilled shaft at Gwangandaero and Suyeong3hogyo are performed and in order to estimate the side friction of the shaft, strain gauges are applied. The bearing capacities from the field test data and the bearing capacity values by the theoretical formula are compared. Even the static load tests didn't reach to the ultimate bearing capacity condition, and all the measured bearing capacity values were higher than those by the theoretical formulas. The field data also showed that the major bearing capacities were not due to end bearings but side friction resistances. Based on the above results, several suggestions are proposed for the drilled shaft design.

• Journal of the Korean Geotechnical Society
• /
• v.23 no.1
• /
• pp.23-37
• /
• 2007

Recently a concept of pile-tip enlarged PHC pile (Ext-PHC pile), for use in the auger-drilled construction method, has been developed and is being implemented in practice. A series of field axial load tests on both PHC and Ext-PHC piles were conducted at an experimental site. In addition, a parametric study on a number of influencing factors was made using a validated finite element model. The field axial load tests indicated an enhanced load-settlement characteristics for the Ext-PHC piles compared with the PHC piles, giving approximately 50% increase in the end bearing capacity. Also found in the results of the parametric study was that the increase in the end bearing capacity of Ext-PHC piles slightly varies with the mechanical properties of supporting ground as well as pile length, in the range of 1.25 to 1.4 time that of PHC. Overall, the results of the field tests as well as the numerical study confirmed that the end bearing capacity of PHC pile can be improved by the concept of.Ext-PHC pile.

• Proceedings of the Korean Geotechical Society Conference
• /
• 2004.03b
• /
• pp.20-27
• /
• 2004

Reinforced twice than width of foundation with SIC under steel piles drived in cohesion soil and in the coal-limestone which heavily fractured. To analyze behaviour characteristic of steel piles, load transfer test was performed to steel piles attached with strain gauges to axial direction. After it passed 49days, dynamic load test was performed to set-up effect of steel piles bearing capacity. The results of test were compared to each other. According to the results, as the skin friction of steel pile was on the same condition, end bearing capacity of steel piles established on SIC solid of cemented milk in cohesion soil was three times than steel piles established on SIG solid of cemented milk in heavily fractured coal- limestone. After piles were driven and passes 49days, in case of piles on SIG solid of comented milk in cohesion soil the increaes of allowable bearing capacity was 442.9% and allowable bearing capacity of piles on SIG solid of cemented milk in heavily fractured coal-limestone increased 22.4%.

• Geomechanics and Engineering
• /
• v.18 no.3
• /
• pp.315-328
• /
• 2019

This paper presents an investigation on bearing capacity, load-settlement behavior and safety factor of rock-soil slopes reinforced using geogrid-box method (GBM). To this end, small-scale laboratory studies were carried out to study the load-settlement response of a circular footing resting on unreinforced and reinforced rock-soil slopes. Several parameters including unit weight of rock-soil materials (loose- and dense-packing modes), slope height, location of footing relative to the slope crest, and geogrid tensile strength were studied. A series of finite element analysis were conducted using ABAQUS software to predict the bearing capacity behavior of slopes. Limit equilibrium and finite element analysis were also performed using commercially available software SLIDE and ABAQUS, respectively to calculate the safety factor. It was found that stabilization of rock-soil slopes using GBM significantly improves the bearing capacity and settlement behavior of slopes. It was established that, the displacement contours in the dense-packing mode distribute in a broader and deeper area as compared with the loose-packing mode, which results in higher ultimate bearing load. Moreover, it was found that in the loose-packing mode an increase in the vertical pressure load is accompanied with an increase in the soil settlement, while in the dense-packing mode the load-settlement curves show a pronounced peak. Comparison of bearing capacity ratios for the dense- and loose-packing modes demonstrated that the maximum benefit of GBM is achieved for rock-soil slopes in loose-packing mode. It was also found that by increasing the slope height, both the initial stiffness and the bearing load decreases. The results indicated a significant increase in the ultimate bearing load as the distance of the footing to the slope crest increases. For all the cases, a good agreement between the laboratory and numerical results was observed.

• Journal of the Korean Geotechnical Society
• /
• v.29 no.12
• /
• pp.105-111
• /
• 2013

The standard penetration test (SPT) has been widely used because of its usability, economy, and many correlations with soil properties among other factors. In SPT, hammer energy is an important factor to evaluate and calibrate N values. To measure hammer energy, an instrumented SPT rod was developed considering that stress waves transferring on rods during SPT driving are the same as stress waves transferring on piles due to pile driving. Using this idea, an instrumented SPT rod with a pile driving analyzer was applied as a pile capacity prediction tool in this study. In order to evaluate this method, SPT and dynamic cone tests with the instrumented SPT rod were conducted and also 2 pile load tests were performed on pre-bored steel pipe piles at the same test site. End bearings were predicted by CAPWAP analysis on force and velocity waves from dynamic cone penetration tests and SPT. Comparing these predicted end bearings with static pile load tests, a new prediction method of the end bearing capacity using the instrumented SPT rod was proposed.