• Proceedings of the Korean Geotechical Society Conference
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• 2000.11a
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• pp.285-292
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• 2000

Though there has been increasing use of large diameter drilled shaft as a foundation structure of bridges, current practice for quality control is to confirm the minimum required load carrying capacity during construction stage. For economic and appropriate design of drilled shaft, it is necessary to evaluate the load transfer mechanism by pile load tests during initial stage of construction and to use the test results as a feedback to a revision of initial design. In this paper, results of load tests peformed at several domestic sites are presented to investigate the load transfer characteristics of large diameter drilled shaft. It was found that most of the load on piles is sustained by shaft friction and that only small portion of the load reaches the bottom of the drilled shaft. Some test results of drilled shaft by Pile Driving Analyzer performed at same sites are also presented to compare the load transfer characteristics interpreted from static pile load tests.

• Journal of the Korean GEO-environmental Society
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• v.16 no.1
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• pp.5-16
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• 2015

In the long span bridge construction, construction cost portion of large scale marine foundation is about 40% (KICTEP, 2007). In this study, designs for deep water depth large composite foundation of a super long span cable-stayed girder bridge of prototype were performed by three design methods (ASD, LRFD, Eurocode) and the behaviors of a large diameter drilled shaft were analyzed and the 3D numerical analysis was performed. As a result, the soft rock socket lengths in allowable stress design estimation method were the longest. The soft rock socket lengths estimated by the design approach 2 among Eurocode and the LRFD were similar. The longer the socket length socketed in the soft rock was, the smaller the axial force acting on a large-diameter drilled shaft head was and the smaller the settlement of drilled shaft was.

• Journal of the Korean Geosynthetics Society
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• v.19 no.2
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• pp.1-11
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• 2020

The lateral bearing characteristics of large diameter drilled shaft depend greatly on the stiffness of the pile, horizontal subgrade reaction of adjacent ground. In particular, the empirical evaluation results of the horizontal subgrade reaction coefficient which are widely used in pile design are very important factors in evaluating the lateral bearing capacity of drilled shaft because the difference in bearing capacity depends on the estimated result. Nevertheless, the evaluation of the horizontal subgrade reaction coefficient on the large diameter drilled shaft is insufficient. In addition, although the range of influence and the location of the maximum moment which is the weaken zone on the pile may be correlated and relationship of these are major consideration in determining the reinforced zone of drilled shaft, the previous studies have not been evaluated it. In this study, the field test and nonlinear analysis of large diameter drilled shaft were performed to evaluate the horizontal subgrade reaction coefficient and to investigate the relationship between the influence range 1/β of the pile and the location of the maximum moment z_m. In the result, the lateral bearing capacity of drilled shaft showed a difference in results by about 190% according to the empirical equation on the horizontal subgrade reaction coefficient. And the relationship between the influence range of the pile and the location of the maximum moment was evaluated as a linear relationship depending on the soil density.

• Proceedings of the Korean Geotechical Society Conference
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• 2004.03b
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• pp.36-43
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• 2004

Most of pile foundations are fixed head condition, but lateral loading test for pile is performed under free head condition generally In this study, a lateral loading test for a large diameter drilled shaft was performed under the fixed pile head and the free pile head condition, where lateral displacement along the pile depth was measure. Test results and theoretical values were compared and analyzed.

• Proceedings of the Korean Geotechical Society Conference
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• 1999.10a
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• pp.431-438
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• 1999

Vertical congressive and horizontal pile load tests were performed to a instrumented large diameter (D : 1,000 mm) drilled shaft. A drilled shaft was penetrated into the weathered soil and weathered rock. PMT was done for evaluation of properties for these strata. It was expected to be difficult to get undisturbed samples of weathered soils and rocks. Thus. PMT was done at the several selected depths. In those strata, to prevent the test bore hole from collapsing, bentonite slurry was used for making the test bore hole. In this study. soil properties was evaluated by means of PMT results and estimating method (direct method, the Memard method) of vertical pile capacity and horizontal pile behaviors were summarized. Also, vertical and horizontal pile capacity were calculated using PMT and pile load test results.

• Proceedings of the Korean Geotechical Society Conference
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• 2005.03a
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• pp.9-16
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• 2005

The purpose of this study is to investigate the settlement characteristics of large drilled shafts embedded into bed rocks. To perform this research, 35 pile load test results for the large drilled shafts are used, because these deep foundations generally used as substructure systems for grand bridges. In case of the yield load can not be easily determined by load(P)-settlement(S) curve from the pile load test at the maximum loads, the standard settlements which can determine a yield load is established. The residual settlement equation of pile embedded in gneiss and igneous rocks is presented in this study. Also a equation is proposed to characterize the relationship between loads and elastic settlements in pile load tests on the large drilled shaft embedded into bedrock. Then, large drilled shaft's settlement characteristics are examined on pile length, pile diameter and pile's socked depth into rock at the pile tip.

• Proceedings of the Korean Geotechical Society Conference
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• 2006.03a
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• pp.486-493
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• 2006

This paper deals with the procedure and the results on the dynamic loading tests of two large diameter - long drilled shafts (diameter=2.0m, length=75m) which were embedded into weathered rocks through thick soft marine clays and sandy gravels. Prior to the real dynamic loading test, the numerical simulation for the test procedure was performed to check the structural stability of the main pile body using equivalent static elastic analysis and the application of the hammer system using WEAP (Wave Equation Analysis of Pile Driving). Through these preliminary analyses the dynamic loading tests on large diameter - long drilled shafts have been successfully achieved.

• Journal of the Korean Geotechnical Society
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• v.20 no.5
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• pp.135-143
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• 2004

In the land section of marine bridge construction site, to confirm the end bearing of large diameter drilled shaft constructed in the fault zone which was discovered unexpectedly, the hi-directional end loading tests were performed. The objectives of this study are to confirm the end bearing of the pile constructed in fault zone and the increasing effect of end bearing after grouting the base ground beneath the pile toe. After grouting the pile base ground, the settlement of pile base decreased considerably and the pile base resistance increased more than twice.

• Journal of the Korean GEO-environmental Society
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• v.5 no.2
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• pp.33-39
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• 2004

Most of pile foundations are a condition of fixed head on pile, but lateral loading test of pile have performed to free head on generally. This study performed field lateral loading test accompanying lateral displacement by depth of pile for two cases(fixed head and free head) and analyzed lateral behavior of large drilled shaft. Furthermore compared theoretical equation with result of lateral loading test.

• Proceedings of the Korean Geotechical Society Conference
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• 2003.03a
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• pp.447-454
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• 2003

In this test, two separated oil jacks were placed at bottom of drilled shaft(D = 1,500mm, L = 33m), and maximum upward and downward load of 1,250 tonf was applied. Also, the deformable rod sensors were placed on each level, and axial strains at each level were measured. Because the side skin friction and the end bearing could be measured separately in the Osterberg type pile load test, this test might be more economical and more applicable than a conventional static pile load test. Thus, if this Osterberg type pile load test could be established during design stage, construction cost might be reduced and its application for large diameter pile could be enhance greatly.