• Proceedings of the Korean Geotechical Society Conference
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• 2004.03a
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• pp.227-247
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• 2004

직접기초(Shallow Foundation)란 상부구조로부터의 하중을 직접 지반에 전달시키는 형식의 기초로써 기초의 최소폭(B)과 근입깊이(D$_{f}$ )와의 비가 대체로 1.0이하인 경우나(Terzaghi, 1943), D$_{f}$ /D$\leq$1-4인 경우에도 직접기초라 정의되었다(Das, 1984). 현재, 깊은 기초보다 이용이 적지만 허용지지력과 허용침하량이 확보되는 지반이라면 깊은기초보다 훨씬 경제적인 설계를 할 수 있는 것이 직접기초이다. 이러한 직접기초의 지지력에 관한 이론적인 기본 개념은 Terzaghi(1943)에 의하여 처음 정립되었고, 그 이후 Meyerhof(1951, 1963), Hansen(1970), Vesic(1973, 1975), Chen(1975) 등에 의하여 각기 다른 지지력 산정식이 제안되었다.(중략)

• Journal of the Korean Geotechnical Society
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• v.15 no.2
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• pp.73-80
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• 1999

Analytical studies on piles so far have been directed toward prediction of bearing capacity under vertical loads. Various static and dynamic formulas have been used in predicting the ultimate bearing capacity of a pile. Further, the reliability of these formulas has been verified by comparing the predicted values with the pile load test measurements. Accordingly, by means of the ultimate load from the data measured by the actual field load tests of PHC piles, safety factors were compared and analyzed static and dynamic formula methods applying to 4 different sites. As a result, the safety factor by Meyerhof formula method indicates 3.0 and the safety factor by Hiley formula method indicates 5.0.

• Proceedings of the Korean Geotechical Society Conference
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• 2005.03a
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• pp.1183-1190
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• 2005

본 논문에서는 백령도 사곶해수욕장의 지반지지력 변화를 알아보고자, 평판재하시험(이하 PBT로 표시함)을 실시하였다. 시험에서 얻어진 데이터는 최대곡률법, logP-logs법, $P-{\triangle}s/{\triangle}(logt)$법을 종합적으로 분석 검토하여 결과값을 산출하였고, 시료를 채취하여 실내실험을 한 결과 통일분류법상 SP의 상태를 나타내었다. 재하시험과 실내실험의 데이터를 비교 분석한 결과, 물다짐의 상태에 따라 침하량의 차이가 2배 가까이 차이를 보였으며, 물다짐이 이루어진 곳의 침하량값이 작고, 허용지지력이 높은 것으로 산출 되었다.

• 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 Society of Hazard Mitigation
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• v.7 no.1 s.24
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• pp.29-38
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• 2007

The research on the track performance and stability of the tilting-train was performed and the settlement of the roadbed was estimated as the tilting train was being operated on the rail joint under the allowable velocity subjected to the track performance and the stability of the tilting-train. Since the impact on the continuous welded rail (CWR) induced by the tilting-train loading is different from the impact on the rail joint, it needs to investigate the settlement of the roadbed beneath the CWR. In this study, when the tilting-train is being operated on the CWR under the allowable velocity subjected to the track performance and the stability of the tilting-train, the settlement and bearing capacity of the roadbed beneath the CWR have been evaluated using numerical analysis and compared with those beneath the rail joint. The numerical results show that the settlements of the roadbed beneath CWR and rail joint are amount to 71.2% and 88.8% of the allowable settlement, respectively. And the stresses are amount to 10.4% and 12.1% of the allowable bearing capacity, respectively.

• The Journal of Engineering Geology
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• v.29 no.3
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• pp.211-222
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• 2019

This study evaluates the yield load and allowable bearing capacity of ground in compressive loading tests to confirm the effect of CPR foundation reinforcement. The average compressive strength of the injection materials was higher than the planned compressive strength. Standard penetration tests for each stratum showed that foundation reinforcement improved the average N values, thereby increasing the bearing capacity of the ground. Compressive loading tests on two CPR piles revealed that the total and net settlement due to the maximum load exceed that permissible for the CPR pile diameter. The yield load and allowable bearing capacity calculated by the settlement criterion and the load-settlement curves varied greatly with the method applied. Therefore, it seems to be necessary to determine the optimum value through comprehensive analysis after applying various yield load calculation methods.

• Journal of the Korean Geotechnical Society
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• v.35 no.12
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• pp.59-67
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• 2019

With the increasing use of geotextile mats in dredging and reclaiming work and coastal construction, the assessment of bearing capacity in soft ground has become an important evaluation index for negligent accidents. The review of the allowable bearing capacity of soft ground consisting of inhomogeneous layers by laying geotextile mats and sand mat layers for soft ground improvement is generally compared with the equation of Meyerhof (1974) and Yamanouchi (1985). Mayerhof formula results in economic loss due to underestimation of bearing capacity, and Yamanouchi (1985) formula does not take into account negligent accidents for punching shear failure, so rather high bearing capacity is evaluated. It is considered that economic feasibility and stability will be ensured by proposing a modified formula to calculate the appropriate bearing capacity by applying the seam tensile strength of the geotextile mat to the design standard of soft ground improvement.

• 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.

• Land and Housing Review
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• v.6 no.3
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• pp.139-145
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• 2015

To improve the pile design efficiency(design bearing capacity/the strength of materials) from 70 percent(160tonf) to 80 percent(190tonf), this paper analysed the existing pile loading test data and performed the precise dynamic loading test and Bi-directional loading test for the first time in Korea. Analysis result of the existing dynamic loading test data by Davisson method showed that bearing capacity of piles penetrated at weathered rock stratum(N=50/15) exceeded 190tonf. But the analysis result by CAPWAP method showed that piles less than the target bearing capacity were 40% due to the lack of impact energy. To get the target bearing capacity from the dynamic loading test, using the hammer over 6tonf to trigger the enough impact energy is necessary. Allowable bearing capacty of Bi-directional static loading test by Davisson method was 260.0~335tonf(ave. 285.3tonf) and exceeded overwhelmingly the target capacity. And this exceeded the bearing capacity of precise dynamic loading test(ave. 202.3tonf) performed on the same piles over 40%. The difference between the capacity of Bi-directional loading test and dynamic loading test was caused by the insufficient impact energy during dynamic loading test and increase by interlocking effect by near piles during Bi-directional static loading test.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.5 no.4
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• pp.23-30
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• 1985

Dynamic pile-driving formulas are widely used in predicting the load capacity of piles in cohesionless soils. However, the accuracy of the formulas has been questioned for a long time due to their oversimplified assumptions and empirical parameters involved in the formulas. The allowable pile capacities calculated by 6 different dynamic pile-driving formulas are compared statistically with the capacities measured in the field, in this paper, to find out the correlations between the calculated capacities and the measured values. The statistical data are then used to evaluate and to adjust the formulas to improve their accuracy. For the greatest accuracy and simplicity of use, it is recommended that the adjusted form of Gates formula be used. When the result of this recommended formula is compared with that of the existing Olson's modified formula, the former is found to be conservative by more than 10 percents.