• Journal of the Korean Geotechnical Society
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• v.34 no.11
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• pp.107-119
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• 2018

PHC piles, extension-plate attached PHC piles, and steel pipe attached PHC piles were installed in field test site. Axial compressive static load tests including load distribution test and Pile Driving Analyzer (after driving) were done on the tip-transformed PHC piles and the grouted tip-transformed PHC piles. Load-displacement curves of three different type of PHC piles, which are PHC pile (TP-1), extension plate attached PHC pile (TP-2) and steel pipe attached PHC pile (TP-3), showed almost the same behavior. Thus bearing capacity increase effect of the tip-transformed PHC piles was negligible. Share ratio of side resistance and end bearing resistance for PHC pile, extension plate attached PHC pile, and steel pipe attached PHC pile were 95.8% vs. 4.2%, 95.6% vs. 4.4%, and 97.8% vs. 2.2% respectively.

• Journal of the Korean GEO-environmental Society
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• v.20 no.3
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• pp.31-38
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• 2019

To determine the optimum dynamic load test analysis for PCFT (Prestressed Concrete Filled steel Tube) hybrid composite piles that PCFT piles are connected to the top of PHC piles, the dynamic load tests and CAPWAP analyses were performed on two hybrid composite piles with steel pipe and PCFT piles as upper piles. The results of the dynamic load tests and CAPWAP analyses showed that the particle velocity measured in PCFT hybrid composite piles was equal to the wave speed of PHC piles when the strain gauges and accelerometers are attached to the surface of inner composite PHC pile after removing the steel pipe in the upper PCFT pile. In addition, when assuming that the material of that upper PCFT pile was the same as that of the lower PHC pile and the cross-sectional area of the steel pipe in upper PCFT pile was converted to that for concrete through the pile model (PM) in CAPWAP analysis, the accuracy of the CAPWAP analysis result for PCFT hybrid composite piles was very high.

• Journal of the Korean Geotechnical Society
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• v.29 no.8
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• pp.53-63
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• 2013

Bored pre-cast piles using PHC piles is widely used in foundation of building structures constructed in urban areas because noise and vibration due to pile installation are low. However, since slime is formed at the base of borehole and the density of bearing stratum surrounding the base of borehole is decreased due to stress relaxation in drilling process of bored pre-cast pile method, the base load capacity of bored pre-cast piles is very low compared to the strength of bearing stratum. In this study, a new type of PHC pile, which short steel pipe with the same diameter as the PHC pile is attached to the pile tip, is developed to increase the base load capacity of bored pre-cast piles. In order to check the effect of the use of new PHC pile on the base load capacity of bored pre-cast piles, field pile load tests are performed for bored pre-cast piles using the new and existing PHC piles. Results of the pile load tests show that the new PHC pile gives higher base load capacity to bored pre-cast piles than the existing PHC pile, since the tip of new PHC pile is penetrated to undisturbed bearing stratum passing through the slime at the base of borehole and the loosened bearing stratum under the slime by pile driving using light hammer.

• Journal of the Korean Geotechnical Society
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• v.32 no.9
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• pp.5-16
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• 2016

New PHC piles, where short steel pipes are attached to the pile toe, are developed to increase the base load capacity of bored pre-cast piles embedded in weathered rock. In this study, new bored pre-cast piles using the new PHC piles are installed at 7 test sites with different soil conditions, and static and dynamic pile load tests are performed to investigate quantitative characteristics on the base load capacity of new bored pre-cast piles. In addition, based on the static pile load test results, a new empirical equation for estimating the base load capacity of new bored pre-cast piles is proposed. A comparison between predicted and measured base load capacities shows that the proposed empirical equation produces conservative predictions for the new bored pre-cast piles. However, the existing design criterion significantly underestimates the base load capacity of new bored pre-cast piles.

• Journal of the Korean Geotechnical Society
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• v.34 no.1
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• pp.37-46
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• 2018

Hollow prestressed concrete filled steel tube (HCFT) piles, which compose hollow PHC piles inside thin wall steel tubes, are developed. In order to investigate the strength characteristics of HCFT piles, flexural and shear tests were conducted on HCFT piles as well as PHC and steel pipe piles with the same diameter. Results of the test program showed that the flexural strength of HCFT piles was 2.88 and 1.19 times those of ICP and steel pipe piles with thickness of 12 mm, respectively, and its shear strength was 2.40 times that of steel pipe piles. The shear key attached to the inside of thin wall steel tube did not affect the flexural behavior of HCFT piles. It was also observed that the flexural strengths of HCFT piles with diameters of 450 and 500 mm were 35 to 63% higher than the sum of the flexural strengths of its components, respectively, because the strength of concrete in compressive zone increased by confining effect of thin wall steel tube on concrete. HCFT piles used as upper piles in hybrid composite piles might decrease the lateral displacement and increase the structural safety of structures subjected to lateral loads.

• Journal of the Korean Geotechnical Society
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• v.16 no.1
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• pp.107-116
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• 2000

Dynamic and static load tests are conducted in four construction sites by using steel pipe piles(SPP) and concrete piles to compare differences of load bearing mechanism. Steel pipe piles are instrumented with electric strain gages and are subject to dynamic load tests during driving. The damage of strain gages attached is checked simultaneously. Static load test is also conducted on the same piles after two to seven days' elapse. Then load-settlement behavior and shaft and/or tip resistances are measured. As a result, the allowable bearing capacity calculated by the Davisson's offset method of CAPWAP analysis shows 2~33% larger than that of static load test. The average value of allowable bearing capacity of static load test is closer to the allowable capacity obtained at the safety factor of 2.5 applied on ultimate bearing capacity than to the one obtained from the Davisson's offset method. The analysis of strain gage readings shows that unit skin friction increases with depth. Furthermore, the friction mobilized around the 1~2m above the pile tip considerably contributes to the total shaft resistance.