• Proceedings of the Korean Geotechical Society Conference
• /
• 2000.03a
• /
• pp.107-141
• /
• 2000

Large diameter piles can be defined as piles with diameter of at least 0.76 m (2.5 ft). In bridge foundation, large diameter piles have been used as pier foundations and their use has been increased greatly. In this study, static pile load tests for large diameter piles peformed in Kwangan Grande Bridge construction site were introduced. Also, various sensor installation methods for several types of piles (that is, open-ended steel pipe pile, drilled shafts and socketed pipe piles), pipe axial load measuring method, load transfer analysis method and pile load test results (pile-head load - settlement curve, and pile axial load distribution curve along the pile depth) were introduced.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.15 no.6
• /
• pp.3872-3878
• /
• 2014

In this study, the dynamic load transfer function, which is necessary for analyzing a pile installed by a vibro hammer, was determined by comparing the results of the analyses and instrumented tests. The static load transfer function was modeled by the Ramberg-Osgood model through an analytical method before determining the dynamic load transfer curve. The parameters of the Ramberg-Osgood model were correlated with the N value of the standard penetration test and average values of the correlation coefficient were 0.97 for the shaft load transfer and 0.98 for the base load transfer. The dynamic load transfer function was simulated using the modified Ramberg-Osgood model. The results showed that there were little differences in the characteristics of dynamic load transfer between the results of the measurement and prediction.

• Proceedings of the Korean Geotechical Society Conference
• /
• 2006.10a
• /
• pp.409-429
• /
• 2006

In designing rock-socketed drilled shaft, bearing capacity evaluation is very important because the maximum values of base and side resistance are not generally mobilized at the same value of displacement, FHWA and AASHTO code suggest different ultimate bearing capacity formular according to rock type and shaft settlement. In domestic code suggest base resistance and side resistance can be added on condition that after confirming the result of field load test with axial load transfer test. This paper shows that static load test and hi-directional load test result analysis of deep rock-socketed drilled shaft in three different sites. Load-settlement curve, t-z, and q-w curve in rock-socketed part were calculated and compared. t-z curve in weathered and soft rock showed no deflection softening behavior in pretty large strain (about 2-3% of diameter). Ultimate resistance could be the summation of side resistance and base resistance in rock-socketed drilled shaft in domestic sites.

• Proceedings of the Korean Geotechical Society Conference
• /
• 2004.03b
• /
• pp.74-81
• /
• 2004

In this study, static end loading tests with load transfer measurement were accomplished for large diameter drilled shaft constructed in fault zone. Yield pile capacity (or ultimate pile capacity) from load-settlement curve was determined and axial load transfer behavior was measurd. The end bearing capacity was increased 2 times due to grouting the toe ground under pile base.

• Proceedings of the Korean Geotechical Society Conference
• /
• 2005.03a
• /
• pp.57-64
• /
• 2005

Since the allowable bearing capacities of piles in weathered/fractured rock are mainly governed by settlement, the load-displacement behavior of the rock socketed pile should be well known. To predict pile head settlement at the design stage, the exact understanding of the load-transfer mechanisms is essential. Therefore, in this research, the load-transfer mechanisms of drilled shaft socketed into weathered rock was investigated. For that, 5 cast-in-place concrete piles with diameters of 1,000 mm were socketed into weathered gneiss. The static axial load tests and the load-transfer measurements were performed to examine the axial resistant behavior of the piles. A comprehensive field/laboratory testing program on weathered rock at the field test sites was also performed to describe the in situ rock mass conditions quantitatively. And then, the effect of rock mass condition on the load transfer mechanism was investigated. The side shear resistance of the pile in moderately weathered rock reached to yielding point at a few millimeter displacements, and after that, the rate of resistance increment dramatically decreased. However, that in the highly /completely weathered rock did not show the obvious yielding point, and gradually increased showing the hyperbolic pattern until with the relatively high displacement (>10 mm). The end bearing-displacement curves showed linear increase at least until with the base displacement of approximately 10 mm, regardless rock mass conditions.

• Proceedings of the Korean Geotechical Society Conference
• /
• 1999.10a
• /
• pp.389-396
• /
• 1999

In this study compressive and tensile load tests have been performed to investigate reinforcing effect and load transfer mechanism of small diameter piles installed in the foundation soil for the marine suspension bridge. Load tests were carried out on steel plate with diameters of 50cm, 100cm and 150cm varying loads starting from 39 tons up to 314 tons. Small diameter piles were proved to behavior like as friction piles and loads were not transmitted to the bottom of piles. From pull-out tests, the uplift capacity of small diameter piles was largely influenced by reinforcing materials compared to frictional resistance between piles and adjacent soils. The bearing capacity of small diameter piles appeared to be higher than the ultimate bearing capacity evaluated using static formulae. The load carrying capacity of small diameter piles was superior to the bored piles with a similar size. Thus, ultimate bearing capacity estimated from static formulae can provide conservative designs and thereby resulting in economic disadvantages. A further study to accumulate data regarding various soil conditions is recommended for an improved estimation of bearing capacity of piles with small diameter.

• Journal of the Korean Geotechnical Society
• /
• v.21 no.5
• /
• pp.187-196
• /
• 2005

Since the allowable bearing capacities of piles in weathered/fractured rock are mainly governed by settlement, the load-displacement behavior of pile should be known accurately. To predict pile head settlement at the design stage, the exact understanding of the load-transfer mechanisms is essential. Therefore, in this research, the load-transfer mechanism of drilled shaft socketed into weathered rock was investigated. For the investigation, five cast-in-place concrete piles with diameters of 1,000 mm were socketed into weathered gneiss. The static axial load tests and the load-transfer measurements were performed to examine the axial resistant behavior of the piles. A comprehensive field/laboratory testing program on weathered rock at the Held test sites was also performed to describe the in situ rock mass conditions quantitatively. And then, the effect of rock mass condition on the load transfer mechanism was investigated. The f-w (side shear resistance-displacement) curve of the pile in moderately weathered rock reached to yielding point at a for millimeter displacements, and after yielding point, the rate of resistance increment dramatically decreased. However, the f-w curve in the highly/completely weathered rock did not show the obvious yielding point, and the resistance gradually increased showing the hyperbolic pattern until relatively high displacement (>15 mm). The q-w (end bearing resistance-displacement) curves showed linear response at least until the base displacement of approximately 10 mm, regardless of rock mass conditions.

• Journal of the Korean Geotechnical Society
• /
• v.36 no.7
• /
• pp.15-28
• /
• 2020

As the skin friction of an embedded pile is produced by the cement paste injected into the borehole, the skin friction cannot be evaluated by the end of initial driving test, which is conducted before the cement paste is cured. In addition, the total resistance of an embedded pile may not be properly evaluated during the restrike test if the base resistance is not fully mobilized because of the insufficient driven energy. The objective of this study is to suggest a new load-settlement curve of embedded piles by combining the results of the end of initial driving and restrike tests. Test piles are installed at fields by using the embedded pile method, and the results of the dynamic pile tests are analyzed using CAse Pile Wave Analysis Program (CAPWAP) after the end of initial driving and restrike tests are conducted. A new load transfer curve, which combines the behaviors of the pile base at the end of initial driving and of the pile shaft at the restrike, is suggested, and a new load-settlement curve is obtained. Subsequently, the resistances of the test piles are evaluated using the combined load-settlement curve, and compared with the results from the end of initial driving and restrike tests. The results showed that the resistances, which are evaluated using the combined load-settlement curve, may overcome the underestimation of the resistance because of the insufficient driven energy. In addition, the resistance resulted from the combined load-settlement curve may be more similar to that from the static load test because the suggested load transfer curve is closer to the behavior of the embedded pile compared to the results of end of initial driving and restrike tests. Therefore, this study demonstrates that the combined load-settlement curve may be effectively used for the evaluation of the bearing capacity of embedded piles.

• KIEE International Transactions on Power Engineering
• /
• v.12A no.1
• /
• pp.15-19
• /
• 2002

The power transfer capability is determined by the thermal, dynamic stability and voltage limits of the generation and transmission systems. The voltage stability depends on the reactive power limit and it affects the power transfer capability to a great extent. Then, in most load flow analysis, the reactive power limit is assumed as fixed, relatively different from the actual case. This paper proposes a method for determining the power transfer capability from a static voltage stability point of view using the IPLAN which is a high level language used with PSS/E program. The f-V curve for determining the power transfer capability is determined using Repeated Power Flow method. It Is assumed that the loads are constant and the generation powers change according to the merit order. The maximum reactive power limits are considered as varying similarly with the actual case and the effects of the varied maximum reactive power limits to the maximum power transfer capability are analyzed using a 5-bus power system and a 19-bus practical power system.

• Geomechanics and Engineering
• /
• v.9 no.3
• /
• pp.313-328
• /
• 2015

In the present study, a CPT-based p-y analysis method was proposed for offshore mono-piles embedded in sands. Static and cyclic loading conditions were both taken into account for the proposed method. The continuous soil profiling capability of CPT was an important consideration for the proposed method, where detailed soil profile condition with depth can be readily incorporated into the analysis. The hyperbolic function was adopted to describe the non-linear p-y curves. For the proposed hyperbolic p-y relationship, the ultimate lateral soil resistance $p_u$ was given as a function of the cone resistance, which is directly introduced into the analysis as an input data. For cyclic loading condition, two different cyclic modification factors were considered and compared. Case examples were selected to check the validity of the proposed CPT-based method. Calculated lateral displacements and bending moments from the proposed method were in good agreement with measured results for lateral displacement and bending moment profiles. It was observed the accuracy of calculated results for the conventional approach was largely dependent on the selection of friction angle that is to be adopted into the analysis.