• Journal of the Korean GEO-environmental Society
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• v.4 no.2
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• pp.65-76
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• 2003

Stone column is a soil improvement method and can be applicable for loose sand or weak cohesive soil. Since the lack of sand, stone column seems one of the most adaptable approach for poor ground as a soil improvement technique. However, this method was not studied for practical application. In this paper, the bearing capacity of single stone column at the Gaduk, Ulsan and Gwangyang under the bulging and general shear failure mode were compared with those of the suggested formulas. Especially, a test result of single stone column at the Busan area by static load was compared with the bearing capacity of suggested formulas. The analysis results showed that there were not much bearing capacity differences among those suggested bearing capacity formulas. However, the bearing capacity by static load test was almost double of those with suggested formula. The result also showed that the undrained shear strength was the most important parameter for the bearing capacity estimation of stone column.

• Journal of the Korean Geotechnical Society
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• v.22 no.10
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• pp.55-67
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• 2006

Modern methods for designing IGM(Intermediate Geomaterial) socketed drilled shafts require knowledge of the compressive strength and modulus of the IGM. However, the weathered IGMs at many sites prohibit the recovery of samples of sufficient length and integrity to test cores in either unconfined or triaxial compression tests. Since rational design procedures usually require values of compressive strength, surrogate methods must be employed to estimate the compressive strength of the IGM. A surrogate method considered in this study was Texas cone penetrometer tests which were performed at several sites in North Central Texas. Correlations of Texas cone penetrometer tests and compressive strengths of cores from these formations are provided in the paper. In order to develop the relationships between Texas cone penetrations and side and base resistance of IGM socketed drilled shafts, three filed load tests were conducted in the same sites. Based on the field study and literature reviews, a design method for IGM socketed drilled shafts using Texas cone penetration test was proposed.

• Journal of the Korean Geosynthetics Society
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• v.21 no.3
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• pp.49-59
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• 2022

This study was conducted to find out the rational and appropriate design of drilled shaft. In other words, in order to find out the variation of ultimate bearing capacity according to the change in the support layer of drilled shaft, back analysis was performed using the bi-directional pile load test performed on drilled shaft. Based on the back-analyzed data, numerical analysis of the pile head load was performed, and the ultimate bearing capacity in the target ground was evaluated using the Davisson method. As a result of numerical analysis of one case where the end of the pile was seated on the top of the weathered rock layer, and three cases where the end of the pile was embedded at different locations in the weathered soil, it was found that sufficient ultimate bearing capacity was secured in all cases. In other words, the case where the end of the pile is seated on the top of the weathered rock layer, not embedded the weathered rock, and the drilled shaft embedded into the weathered soil also have sufficient bearing capacity, so it can be used as a support layer for drilled shaft.

• Journal of the Korean Geotechnical Society
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• v.27 no.12
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• pp.97-106
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• 2011

To analyze the lateral load-deflection behavior of steel-concrete composite drilled shafts, a series of lateral pile load tests were performed. The test results were compared with the results from various analytical methods for lateral pile behaviors using the coefficients of subgrade reaction ($k_h$) estimated by pressuremeter test (PMT) and standard penetration test (SPT). As a result, it was found that the analytical methods using the $k_h$ estimated by SPT N value were not suitable for evaluating the pile head lateral load-deflections of the piles within the allowable deflection. However, the methods using the $k_h$ calculated from PMT were able to represent the initial lateral behavior at the head of the piles fairly well. Also, the method by the pressuremeter curve, which was applied directly to the p-y curve of the piles, offered a reasonable lateral behavior estimation by applying the correction factor to the pile materials.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.13 no.5
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• pp.223-234
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• 1993

The main characteristics of PHC piles is that silica material and autoclave curing technique are used when manufacturing to have higher strength than PC piles. In this paper, pile drivability and bearing capacity characteristics of the PHC piles are studied through numerical analysis based on wave propagation theory, driving records and pile load tests in situ. It is found that we can have higher bearing capacity by using the PHC piles rather than the PC on condition that the most effective driving equipment is chosen when driving the pile. In other words, since the PHC piles have higher resistance to driving energy, the heavier ram can be used in the driving process, which results in the higher bearing capacity.

• 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.23 no.6
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• pp.37-51
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• 2007

In this study, pile load tests have been carried out to develop new P-y curves and then, to investigate the effects of pile rigidities on laterally loaded offshore drilled shafts in Incheon marine clay. This paper consists mainly of two parts: the first part, performance of a series of lateral load tests on small- and full-scale piles under one- and two-way loadings and the second part, comparison between the measured and predicted results by using O'Neill's and Matlock's clay models. Based on the results obtained, it is shown that relatively good agreements in bending moments and lateral displacements were obtained between the measured results using calculated P-y curves and predicted ones by O'Neill's and Matlock's clay models. The cases were considered with varying rigidity factors based on pile diameter, length and subgrade soil reaction. Through comparisons, it is found that soil P-y curve influences highly the behavior of flexible pile rather than that of rigid pile.

• Journal of the Korean Geotechnical Society
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• v.37 no.11
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• pp.7-22
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• 2021

In this study, inverse analysis was performed on the bi-directional axial compressive load test conducted on drilled shafts. And the bearing capacities were analyzed by numerical analysis of various pile tip ground conditions of silt clay, silt sand, sand silt, sand gravel, weathered rock, and soft rock. The bearing capacities were analyzed using the P-S method, the Davisson method, and the allowable sttlement of 25.4 mm. The minimum allowable bearing capacities analyzed by three methods were found to be 19.64 MN ~ 24.96 MN. At this time, the base resistances were sharing a 2% ~ 12% of a head load, shaft resistance were shared 88% ~ 98% of the head load. The greater the strength of pile tip was found to increase the allowable bearing capacity. However, the difference between the maximum allowable bearing capacity and the minimum allowable bearing capacity was 5.32 MN, and the increase in the allowable bearing capacity was only 27% depending on the pile tip.

• Journal of the Korean GEO-environmental Society
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• v.6 no.3
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• pp.47-54
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• 2005

In many practical cases, design methods of pile have been used mainly semi empirical bearing capacity equations. It can be done that confirmation of pile bearing capacities through using of dynamic and static tests during constructing or after constructions. If a prediction of layered point pile bearing capacity could be done through simple tests during field investigation, it could be done that more reliable design of pile than a prediction of using semi empirical equations or static formulations. This paper suggests a method to estimated point bearing capacity during in-situ investigation by using the dynamic rod model pile and verifies the point bearing capacity compare with results of static pile load tests. From test results, the unit ultimate point bearing capacities are relatively similar through a dynamic rod model pile tests and static pile load tests. The unit ultimate point bearing capacity by using N value is shown about 50 % value of measured unit ultimate point bearing capacity from field test result and the prediction of the unit ultimate point bearing capacity by using N value is shown very conservative, illogical and uneconomical pile designs.

• 기술발표회
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• s.2006
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• pp.115-132
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• 2006

본 글은 부산-김해간 경량전찰 건설공사의 기초설계시 현장타설말뚝 기초의 지지층을 모래자갈층으로 적용한 사례이다. 낙동강 유역은 퇴적층이 발달하여 풍화암 이상의 기반암층이 지표하 60~80m 이후에서 출현하며, 40m 이상의 심도에서 매우 조밀한 상태의 모래자갈층이 10-20m 두께로 분포하고 있어, 모래자갈층을 관통하여 기반암에 말뚝기초를 지지할 경우 기초공사에 상당한 기간이 소요될 뿐만 아니라, 시공성과 경제적인 측면에서 매우 불리하다. 이에 대한 개선방안으로 대구경 현장타설말뚝을 N치 50 이상의 조밀한 상태의 모래자갈층에 지지하였으며, 인근현장의 적용사례, 기초 구조물 안전성 검토 및 현장재하시험 등의 비교분석을 통하여 모래자갈 지지층의 적정성을 확인하였다. 따라서, 풍화암 이상의 지지지반 출현심도가 60m 이상으로 매우 깊고, 지지지반 상부에 모래자갈층이 두껍게 분포하는 경우에는 모래자갈층을 말뚝기초의 지지층으로 활용하는 방안이 시공성 및 경제성 측면에서 합리적이라 판단된다.