• Journal of the Korean GEO-environmental Society
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• v.3 no.4
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• pp.51-58
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• 2002

In Korea, drilled shaft are generally socketed into rock. Driven pile has environmental problems such as vibration and noise, therefore, the applications of the drilled shaft are increasing in Korea. In this paper, static load test data of the rock socketed drilled shaft at Gwangandaero and Suyeong3hogyo are analyzed. The bearing capacities from field test data and theoretical formula are compared and analyzed. From this study, design approaches for drilled shafts in Korea are examined and several suggestions are proposed.

• Journal of the Korean GEO-environmental Society
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• v.4 no.2
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• pp.5-13
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• 2003

The domestic design method for the shaft resistance of drilled shafts into a bedrock is based on the empirical method, where the uniaxial compressive strength of rock specimen is utilized for calculation of the shaft resistance. This method has uncertainties in prediction of capacity of drilled shafts and result in uneconomic engineering design. Recently a new improved design method was suggested, which reflects important factors that affect the strength of pile sockets. Socket roughness is one of the significant factors influencing the shaft resistance of drilled shaft socketed into rock. In this paper roughness information for the shaft resistance design of socket pile was suggested on the basis of statistical analysis of data measured from wall surface in the bore holes of drilled shafts.

• Proceedings of the Korean Geotechical Society Conference
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• 1999.03a
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• pp.193-200
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• 1999

An experimental study is described in which a 305-mm-diameter instrumented drilled shaft was installed in a moderately expansive clay soil during the dry season and monitored over a period of about 18 months. The purpose of the study was In investigate the effects of seasonal moisture changes in the soil on the shear stresses imposed on the sides of the drilled shaft and movements of the shaft head. The soil in the vicinity of the test shaft was instrumented to measure suction and ground surface movement and the relation between suction, total stress and shear strength of the soil at the test site was determined through laboratory triaxial compression testing. Daily rainfall and temperatures were also monitored at the test site, the National Geotechnical Experimentation Site at the University of Houston, where control on surface grading and vegetation existed. Over the course of the study induced unit side shear values of up to 54 kPa were measured in the test shaft. A simple computational model was developed that related observed suction changes to unit side shear induced by the expansion of the soil through the use of the laboratory suction-total stress-shear strength relation.

• Proceedings of the Korean Geotechical Society Conference
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• 2005.03a
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• pp.1-8
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• 2005

In this study, static pile load tests for instrumented drilled shaft pile and instrumented driven steel pipe pile were performed. Based on the results of pile load test, skin friction of each stratum was compared. Skin friction of drilled shaft were more than those of driven pile at the same settlement. This was based on the difference of surface roughness of piles and pile construction methods.

• Proceedings of the Korean Geotechical Society Conference
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• 2006.10a
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• pp.585-592
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• 2006

Recently, many high rise buildings is planning and under construction over the world. The drilled shafts as a foundation of high rise buildings are often adopted fur the purpose of construction safety and construction cost effectiveness. It is common that the capacity of drilled shafts is beyond conventional conception. The reasonable design and quality assurance for the drilled shaft as foundation of high rise building become much more important since the drilled shafts should bear much higher working load. This paper reviews state of the art of the design and quality assurance for the drilled shafts as foundation of high rise buildings. And also some related suggestions are given in this paper.

• 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.

• Journal of the Korean Geotechnical Society
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• v.19 no.4
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• pp.95-105
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• 2003

The existing design criteria f3r the estimation of ultimate bearing capacity of drilled shaft socketed into rock masses are mainly obtained from the ultimate pile load capacities, which are determined by inconsistent failure criteria. Therefore, these design criteria generally produce difffrent predictions even for drilled shaft in the same condition. In this paper, the accuracies of the existing design criteria are investigated to develop an optimized design process for drilled shaft socketed into rock masses. Reasonable and consistent ultimate capacities of drilled shafts socked into rock masses, necessary far the check of accuracies of predictions, are determined by applying a specific failure criterion to a total of 11 pile load test results. A comparison between the predicted and the measured load capacities shows that ultimate base load capacities calculated from Zhang and Einstein's equation and NAVFAC are close to the measured values. Rosenberg and Journeaux's equation produces satisfactory prediction f3r ultimate side load capacity.

• Journal of the Korean GEO-environmental Society
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• v.7 no.6
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• pp.101-111
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• 2006

In case of drilled shafts installed by drilling through soft overburden onto a strong rock, the piles can be regarded as end-bearing elements and their working load is determined by the safe working stress on the pile shaft at the point of minimum cross-section or by code of practice requirements. Drilled shafts drilled down for some depth into weak or weathered rocks and terminated within these rocks act partly as friction and partly as end-bearing piles. The base resistance component can contribute significantly to the ultimate capacity of the pile. However, the shaft resistance is typically mobilized at considerably smaller pile movements than that of the base. In addition, the base response can be adversely affected by any debris that is left in the bottom of the socket. The reliability of base response therefore depends on the use of a construction and inspection technique which leaves the socket free of debris. This may be difficult and costly to achieve, particularly in deep sockets, which are often drilled under water or drilling slurry. As a consequence of these factors, shaft resistance generally dominates pile performance at working loads. The efforts to improve the prediction of drilled shaft pile performance are therefore primarily concerned with the complex mechanisms of shaft resistance development. In this study, the numerical analyses are carried out to investigate the behavior characteristics of side of rock socketed drilled shafts varying the loading condition at the pile head. The difference of behavior characteristics of side resistance is also evaluated with the effects of modelling of asperity.

• 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.

• Journal of the Korean Geotechnical Society
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• v.23 no.9
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• pp.51-63
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• 2007

Behavior of rock-socketed drilled shafts subjected to axial load was investigated on the basis of pile load tests. The emphasis was laid on analyzing the shear load transfer characteristics from the shafts to surrounding rock. Field load tests were performed on nine test shafts under various conditions such as weathering of rock mass, borehole roughness, pile diameters, and loading directions. The borehole roughness at each test site was profiled using a laser borehole profiler. In order to evaluate and to propose ultimate shaft resistance($f_{max}$) of drilled shafts in rock of Korean peninsular, also, database of pile load tests was developed by reviewing various literature and technical reports.