• Geotechnical Engineering
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• v.7 no.3
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• pp.51-64
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• 1991

The reliable estimation of pile bearing capacity is essential for the improvement of the re- liability and the cost-effectiveness of the design. There have been numerous pile bearing capacity prediction methods proposed up to now, however, execpt for the estimation made from the result of the pile loading test, not one method is appropriate for the reliable prediction. Due to the considerable time and expenses required to carry out the pile loading test, the test has seldom been utilized. The development of Simple Pile Loading Test(SPLT) which utilizes the pile skin friction as the required reaction force to cause the pile tip settlement, provides a solution to perform more pile loading tests and consequently a more economical pile design is possible. The separate measurement of skin friction and tip resistance during the course of performing SPLT provides a better understanding of the pile behavior than the result of the conventional pile loading test where only the total resistance is measured. On the other hand, there are some points to be clarified in order to apply the test results of SPLT to practical problem. They are the direction of the applied load to mobilize the skin friction and the use of reduced sized sliding core. In this research, both the SPLT and the conventional pile loading test on 406mm diameter steel pipe pile have been performed. From the result, it would be safe to use the measured SPLT skin friction value directly in the design, since the value is somewhat lower than the value measured in the conventional test. It is further assumed that the tip resistance value of the reduced sized sliding core should properly be analysed by taking the incluonce of scale effect into consideration.

• Journal of the Korean Geotechnical Society
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• v.35 no.3
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• pp.5-16
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• 2019

With the recent concentration of urban populations, the constructions of large structures are increasing, along with the development of foundations for large structures. PHC Piles have been used in many structures ever since Japanese introduced the technology at the end of the 20th century. Recently, many studies on the use of the PHC Pile have been carried out as earth retaining using the merits of PHC piles. In this study, static axial compression tests were conducted on the PHC-W piles constructed as column-type in building underground additional wall using the PHC-W earth retaining wall. The end bearing capacity of pile was calculated using the axial load transfer measurement that was obtained from the static axial compression test result. Since end bearing capacity of the PHC-W pile embedded in weathered rock showed a different behaviour from the conventional PHC pile, the calculation method of end bearing capacity for column-type PHC-W piles would be proposed. The unit ultimate end bearing equation proposed for single and group PHC-W pile embedded in weathered rock is $q_b=13.3N_b$ and $q_b=6.8N_b$.

• Journal of the Korean Geotechnical Society
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• v.23 no.5
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• pp.15-27
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• 2007

This paper deals with the bearing capacity behaviour of geosynthetic-reinforced stone column(GRSC) constructed in soft ground, as part of an investigation regarding the applicability of GRSC in Korea. In this study, two-dimensional finite element analyses were performed to investigate the effect of relevant design factors on the bearing capacity behaviour. The parametric study is performed for various influencing factors. The results indicated that the geogrid encasement tends to significantly improve the load carrying capacity of a stone column. Also found were that the geogrid encasement length and its stiffness significantly affect the load carrying capacity behaviour of GRSC, and that the encasement length of three times the stone column diameter is sufficient in mobilizing the full reinforcement effect. Practical implications of the findings are discussed.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.22 no.1
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• pp.1-9
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• 2010

Pile reinforcement systems with enlarged upper section are newly introduced by using a mechanism that most of horizontal forces are resisted in the upper part of the pile. The new systems are expected to be effectively applicable to the marine structures including port and harbor facilities. In this study, three different reinforcement methods such as bucket pile type, top base pile type, and grouting reinforcement type were utilized in the 3-D. numerical simulations. The parametric study deals with the effects of various factors including soil types and stratigraphy, reinforcement methods, type and dimension of the pile on the lateral behaviors of the pile. The results show that the reinforcement method with bucket pile is the most efficient one compared to the top base pile type and grouting reinforcement type.

• Journal of the Korean Geosynthetics Society
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• v.18 no.4
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• pp.263-272
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• 2019

This paper describes the results of bearing capacity using field loading test of pile, in order to extend the applicability of drilled shaft with mid-size, and the results were compared with the prediction results of design bearing capacity by empirical formular. The static load test result showed that the allowable bearing capacity of high pile strength was about 2.4 times higher than that of low pile strength. The dynamic load test result showed that the allowable bearing capacity of high pile strength was about 1.4 times~1.5 times higher than that of low pile strength. The comparison result of allowable bearing capacity between static and dynamic load test showed that the difference of allowable load ranged from 3% to 6% under the same settlement conditions. As a result of comparing the ultimate bearing capacity by load test and design bearing capacity, it was found that the FHWA proposed equation could be more reasonable than the other proposed equation in load sharing ratios of end bearing and skin friction.

• Journal of the Korean Geotechnical Society
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• v.29 no.7
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• pp.17-36
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• 2013

In this paper, the empirical relations of skin friction and end bearing resistance with the results of site investigation in soft rock are proposed through the analysis of bi-directional pile load tests of rock socketed drilled shafts performed at large offshore bridge foundations and high-rise building projects (13 test piles in 4 projects). The site investigation and drilling for bi-directional pile load tests were performed at the centers of test piles, and f-w curves for skin friction and q-w curves for end bearing were plotted based on load-transfer measurements. From the above curves, the empirical relations of skin friction and end bearing resistance with the results of site investigation depending on the mobilized displacement are determined by multiple regression analysis and compared with previous studies. Since the f-w and q-w curves of rock-socketed piles in Korea show hardening behavior according to mobilized displacement, the developed empirical relations by the mobilized displacement are more reasonable than those of previous studies which could not consider the mobilized displacement and suggested the ultimate capacity with unconfined compressive strength only. Particularly, the developed equations correlated with unconfined compressive strength show the best correlations among the equations correlated with other parameters.

• Journal of the Korean Geotechnical Society
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• v.21 no.10
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• pp.73-83
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• 2005

Recently, foundation designs based on piled raft concept have been increasing, where the piles are required not to ensure the overall stability of the foundation but to act as settlement reducer. When a concrete track is constructed on soft ground, excessive settlements may occur, while it rarely has bearing capacity problems. In this case, the settlement of the concrete track may be effectively reduced by arranging a small number of small-diameter piles beneath the track. This paper presents the effect of pile installation on the reduction of concrete track's settlement. A 3D finite difference method was employed to model the piled concrete tracks. A parametric study was carried out to assess the effect of varying soil condition and pile arrangements. From the analysis results, it is verified that the effect of the pile installation is significant to effectively reduce the settlement of concrete track. Optimal number of pile rows and pile spacings was proposed for the economical design of a piled concrete track. The bearing mechanism of piles was also investigated by analyzing load sharing characteristics of pile according to soil conditions and pile arrangements.

• Journal of the Korean Geotechnical Society
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• v.33 no.6
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• pp.17-25
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• 2017

In this research, post grouting methods were applied on PHC piles, and static load tests were conducted to confirm the effect of post grouting on bearing capacity enhancement of PHC piles. Grouting pressures of 1.9 MPa and 3.5 MPa were applied, and bearing capacities of grouted piles were compared with that of non-grouted pile. From the static load test results, the bearing capacities of grouted piles were about 3 times higher than that of non-grouted pile. In addition, the design efficiency (allowable bearing capacity/nominal bearing capacity) increased from 32% to 97% after post grouting, and the axial stiffness of piles also increased by about 1.3 times per grouting pressure.

• Geotechnical Engineering
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• v.11 no.2
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• pp.19-28
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• 1995

Based on the various test data acquired in the field, the large pressure chamber and the small pressure chamber, uplift behaviors and method of determining the ultimate uplift capacity of pile driven in small pressure chamber were studied. After uplift pile experienced 2 or 3 sudden slip due to increase of uplift load, complete pullout failure was occurred. Thus, it appears that the ultimate uplift capacity could be identified as the load at displacement where first slip occurs. The ultimate uplift capacity might be determined in every test and the disturbance after first uplift test could be recovered by adding one blow of the drop hammer, which had to depend on the model pile capacity.

• Journal of the Korean Geosynthetics Society
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• v.10 no.1
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• pp.1-8
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• 2011

The problems like a deterioration of loading bearing capacity, an exaggeration of settlement and lateral deformation are able to be generated, meanwhile structures are built in soft ground. Top-Base method is belonged to a rigidity mat foundation method which is used to surface treatment of soft ground. This method makes an effect to increase the bearing capacity of foundation using friction force, and prevent the differential settlement. Further more, the In-Situ Top-Base method has advantages in the phase of economic effect by reduction of the construction cost and offers an expediency on construction comparing with precast products. This paper presents the way of the estimation of bearing capacity for In-Situ Top-Base method through field plate load test in soft ground. It utilizes the results to a future design by analyzing the properties in the existing study and designs through these analysis and calculating the top-base method's reasonable range.