• Journal of the Korean Geotechnical Society
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• v.25 no.7
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• pp.23-33
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• 2009

In this study the characteristics of piled raft was investigated by using both centrifuge and numerical modeling. The ultimate bearing capacities of single pile, unpiled raft, freestanding pile group and piled raft were compared in order to investigate load sharing of each element : pile and raft. The comparison determined parameters to simply evaluate the ultimate bearing capacity of piled raft. Centrifuge test results were simulated by numerical simulation to verify the parameters.

• Journal of the Korean Geosynthetics Society
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• v.11 no.3
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• pp.11-17
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• 2012

This paper presents the results of investigation into bearing capacity of a geocell reinforced load base. In order to analyze variation of bearing capacity of the geocell reinforced road base comparing to without reinforced geocell road base, a series of full-scale tests were performed and measured using FWD (Falling Weight Deflectometer). The results indicate that bearing capacity of geocell (T=1.5 mm) reinforecd road base increase than the unreinforced road base.

• Journal of the Korean Geosynthetics Society
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• v.19 no.1
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• pp.65-73
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• 2020

This study describes the evaluation results of pile length ratio and N value on the bearing capacity of drilled shafts in cohesionless soil. The bearing capacity ratio in Meyerhof's formula is affected only by the length ratio, and it is equally evaluated a sharing ratio of the end bearing capacity and the skin friction. NAVFAC's formula shows that the pile length influences both end bearing capacity and the skin friction, but pile length is also found to be a more influence factor on the end bearing capacity. Especially, it was found that the effect of pile length factor was larger than the effect of N value and pile diameter. FHWA's formula was evaluated to reflect the influence factor by skin friction more positively than other formulas at calculation the bearing capacity. It was also confirmed that the influence of the skin friction is larger when the ultimate bearing capacity is evaluated.

• Journal of the Korean Geotechnical Society
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• v.22 no.8
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• pp.5-11
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• 2006

A series of large scale plate loading tests are performed to assess bearing capacity characteristic of dredged and reclaimed ground that is reinforced by bamboo net and geotextile as a surface strengthen method. Bearing capacity ratio is distributed from 3.46 to 6.03 for bamboo net and from 2.19 to 3.59 for Geotextile In case of bamboo net, BCR was obtained from 1.6 to 1.7 times than Geotextile. As the comparison of each bearing capacity from test and theory shows, bearing capacity theory for geotextile was not suited for bamboo net. The bearing capacity analysis reinforced by bamboo net shows a good relationship between sand mat thickness (H) / bamboo net space (S), and bearing capacity ratio (BCR).

• The Journal of Engineering Geology
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• v.30 no.4
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• pp.635-648
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• 2020

Performance improvement of helical piles in static load tests using hexagon joints that do not require welding or bolting was investigated. Two sites were selected for pile field tests to evaluate their bearing capacity. Static and pull-out load tests were undertaken to assess the method for estimating bearing capacity. The field tests indicated that the bearing capacity of the gravity grout pile was ≥600 kN in the static load test, consistent with the AC 358 Code. The non-grout pile had a bearing capacity of ≤600 kN, suggesting that gravity grouting is required. Field pile load-test results were used to establish the bearing capacity equation, based on a small number of helical pile.

• Journal of the Korea institute for structural maintenance and inspection
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• v.14 no.3
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• pp.178-185
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• 2010

This paper presents the evaluation of foundation stability according to decrease of the foundation contact area on the ground. In order to carry out this research, the experimental and numerical studies are performed. In the experimental study, the carefully controled laboratory model tests are carried out with different foundation size and types. The model test results are analyzed and interpreted by analytical and numerical calculation in order to verify both results obtained from experimental and numerical studies. It is clearly found from the results that the foundation stability is considerably reduced when the foundation contact area ratio is less than 75%. This research may be very useful to develop the economical foundation type.

• Journal of the Korean Geotechnical Society
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• v.34 no.7
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• pp.39-49
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• 2018

Jacked pile that involves the use of hydraulic jacks to press the piles into the ground is free from noise and vibration, and is possibly installed within a limited construction area. Thus, as an alternative to conventional pile driving methods, pile jacking could become widely accepted for the construction projects in urban area (e.g., reconstruction or remodeling construction projects). Great concern has arisen over the prediction of axially loaded jacked pile behavior. Against this background, a series of pile load tests were hence conducted on a jacked steel pipe pile installed in weathered zone (i.e., weathered soil and weathered rock). From the test results, base resistance and shaft resistance for each test condition were evaluated and compared with the values predicted by the previous driven pile resistance assessment method. Test results showed that the previous driven pile resistance assessment method highly underestimated both the base and shaft resistances of a jacked pile; differences were more obviously observed with the shaft resistance. The reason for this discrepancy is that a driven pile normally experiences a larger number of loading/unloading cycles during installation, and therefore shows significantly degraded stiffness of surrounding soil. Based on the results of the pile load tests, particular attention was given to the modification of the previous driven pile resistance assessment method for investigating the axially loaded jacked pile behavior.

• Journal of the Korean Geotechnical Society
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• v.38 no.10
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• pp.61-74
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• 2022

Considering that the number of cases in which a structure foundation is located on weathered rock has been increasing recently, for adequate design bearing capacity of a foundation on weathered rock, allowable bearing capacities of such foundations in geotechnical investigation reports were studied. With reference to the study results, the allowable bearing capacity of a foundation on weathered rock was approximately 400-700 kN/m², with a large variation, and was considered a conservative value. Because the allowable bearing capacity of the foundation ground is an important index in determining the foundation type in the early design stage, it can have a significant influence on the construction cost and period according to the initial decision. Thus, in this study, six large-scale plate-bearing tests were conducted on weathered rock, and the bearing capacity and settlement characteristics were analyzed. According to the test results, the bearing capacities from the six tests exceeded 1,500 kN/m², and it shows that the results are similar with the one of bearing capacity formula by Pressuremeter tests when compared with the various bearing capacity formula. In addition, the elastic modulus determined by the inverse calculation of the load-settlement behavior from the large-scale plate-bearing tests was appropriate for applying the elastic modulus of the Pressuremeter tests. With consideration of the large-scale plate-bearing tests in this study and other results of plate-bearing tests on weathered rock in Korea, the allowable bearing capacity of weathered rock is evaluated to be over 1,000 kN/m². However, because the settlement of the foundation increases as the foundation size increases, the allowable bearing capacity should be restrained by the allowable settlement criteria of an upper structure. Therefore, in this study, the anticipated foundation settlements along the foundation size and the thickness of weathered rocks have been evaluated by numerical analysis, and the foundation size and ground conditions, with an allowable bearing capacity of over 1,000 kN/m², have been proposed as a table. These findings are considered useful in determining the foundation type in the early foundation design.

• Journal of the Korean Geotechnical Society
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• v.23 no.3
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• pp.61-75
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• 2007

Deep foundations have been popularly installed in hard stratum such as gravels or rocks in Korea. However, it is necessary to consider sand or sandy gravel layers that locate at the mid-depths as the bearing stratum of piles in the thick Nakdong River deltaic deposits, as done in the Chaophraya (Bangkok) and Mississippi River deltas. This study was focused on the finding of suitable methods for estimating bearing capacity when driving prestressed high-strength concrete (PHC) piles to a required depth in the deltaic area. Ground investigation was performed at five locations of two sites in the deltaic area. Bearing capacity of the driven piles has been computed using a number of proposed methods such as CPT-based and other analytical methods, based on the ground investigation and comparison one another other. Five PDA (pile driving analyzer) tests were systematically carried out at the whole depths of embedded piles, which is a well-blown useful technique for the purposes. As the results, the bearing capacities calculated by various methods were compared with the PDA and static load testing results. It was found that the shaft resistance is significantly governed by set-up effects and then the long-term value agrees well with that of the $\beta$ method. Also, the design methods for toe resistance were determined based on the SLT result, rather than PDA results that led to underestimation. Moreover, using the CPT results, appropriate methods were proposed for calculating the bearing capacity of the piles in the area.

• Journal of the Korean GEO-environmental Society
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• v.23 no.12
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• pp.5-15
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• 2022

Conventionally, because evaluation methods of the bearing capacity for double steel pipe-concrete composite pile design have not been established, the conventional vertical bearing capacity equations for steel hollow pile are used. However, there are severe differences between the predictions from these equations, and the most conservative one among vertical bearing capacity predictions are conventionally adopted as a design value. Consequently, the current prediction method for vertical bearing capacity of composite pile prediction composite pile causes design reliability and economical feasibility to be low. This paper investigated mechanical behaviors of a new composite pile, with a cross-section composed of double steel pipes filled with concrete (DSCT), vertical bearing capacities were analyzed for several DSCT pile conditions. Axisymmetric finite element models for DSCT pile and surrounding ground were created and they were used to analyze effects on behaviors of DSCT pile pile by embedding depth, stiffness of plugging material at pile tip, height of plugging material at pile tip, and rockbed material. Additionally, results from conventional design prediction equations for vertical bearing capacity at steel hollow pile tip were compared with that from numerical results, and the use of the conventional equations for steel hollow pile was examined to apply to that for DSCT pile.