• Proceedings of the Korean Geotechical Society Conference
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• 2008.10a
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• pp.691-699
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• 2008

In the design of a foundation, settlement of the foundation may exceed allowable design criteria even with a competent bearing stratum. In such a case, a piled-raft foundation system may be adopted using piles as settlement reducing component. In this paper, Disconnected Piled Raft Foundation (DPRF) system, which installs disconnected piles underneath the raft and uses the piles as ground reinforcements, is studied as a cost effective design method against the classical piled-raft foundation system. To this end, large size loading tests were carried out on weathered ground changing area replacement ratio and length of piles. The results indicated that the settlement of the reinforced ground was reduced by 34~87% and the allowable bearing pressure increased by 70% on average from those of the unreinforced original ground, respectively. The correlating formula between the area replacement ratio and the load bearing ratio of piles were derived from the test results and numerical analysis. From the correlation, a design method determining the size and the quantity of the disconnected piles to enhance the bearing capacity of original ground to the desired value was proposed based on one inch settlement criteria.

• Journal of the Korean Geotechnical Society
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• v.24 no.5
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• pp.37-54
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• 2008

The standard construction manual of the SDA (Separated Doughnut Auger) piling method was proposed so that the resisting capacity of the augered piles could work effectively. 438 dynamic pile load tests were performed on 379 test piles, which were installed at 36 sites in Korea by the SDA piling method with application of various water-cement ratio of cement milks. The dynamic pile load test results showed that the bearing capacity of the SDA augered piles depended on the water-cement ratio of cement milks. And couple of the formulas were presented according to water-cement ratio and various grounds to estimate quantitatively both the unit end bearing and the unit frictional capacity of the SDA augered piles. It was also considered that the water-cement ratio of cement milks exerts an influence on the bearing capacity of the SDA augered piles. The presented formulas were compared with the existing formulas, which were presented by several standard design codes to design the augered piles.

• Proceedings of the Korean Geotechical Society Conference
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• 2005.03a
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• pp.705-712
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• 2005

Among soft ground treatment methods with granular soil used in domestic, the sand compaction pile method has been utilized greatly, but, as a result of exhaustion of sand and increase of unit cost, a necessity of an alternative method is suggested. In this study, the static load tests for group crushed-stone compaction piles which were constructed at in-situ site were performed. Pile diameter was 700mm and area of loading plates were changed. The static load tests of single and group piles were performed for area replacement ratio of 20, 30 and 40%. Based on test results, bearing capacity of group crushed-stone compaction pile were estimated. The more both single pile and group pile increase, the more yield bearing capacity tended to increase. Also, the yield bearing capacity of a group pile is about 50% less than the yield bearing capacity of a single pile. If the ground reinforced with the crushed-stone compaction pile is replacement ratio of $20{\sim}40%$, RIYB of both single pile and group pile increases qualitative tendency of linear more than original ground

• Proceedings of the Korean Geotechical Society Conference
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• 2002.03a
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• pp.397-404
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• 2002

The bearing capacity of open-ended piles is affected by the degree of soil plugging, which is quantified by the IFR. There is not at present a design criterion for open-ended piles that explicitly considers the effect of IFR on pile load capacity In order to investigate this effect, model pile load tests using a calibration chamber were conducted on instrumented open-ended piles. The results of these tests show that the IFR increases with increasing relative density and increasing horizontal stress of soils. The unit base and shaft resistances decrease with increasing IFR. Based on the results of the model pile tests, new empirical relations for base load capacity and shaft load capacity of open-ended piles are proposed. In order to check the accuracy of predictions made with the proposed equations, the equations were applied to the full-scale pile load test preformed in this study, Based on the comparisons with the pile load test results, the proposed equations appear to produce satisfactory predictions.

• Geomechanics and Engineering
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• v.18 no.4
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• pp.363-371
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• 2019

In this study, the load carrying behavior of piled rafts installed in inclined bearing rock layer was investigated for rock-mounted and -socketed conditions. It was found that settlements induced for an inclined bearing rock layer are larger than for a horizontal layer condition. The load capacity of piled rafts for the rock-mounted condition decreased as rock-layer inclination angle (${\theta}$) increased, while vice versa for the rock-socketed condition. The load capacities of raft and piles both decreased with increasing ${\theta}$ for the rock-mounted condition. When bearing rock layer was inclined, loads carried by uphill-side piles were greater than those by downhill-side piles. The values of differential settlements of rock-mounted and -socketed conditions were not significantly different whereas slightly higher for the rock-socketed condition. The values of load sharing ratio (${\alpha}_p$) and its variation with settlement were not markedly changed by the inclination of bedrock. It was shown that ${\alpha}_p$ for piled rafts installed in rock layer was not affected by ${\theta}$ whereas actual loads carried by raft and piles may vary depending on the pile installation and rock-layer inclination conditions.

• 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.

• Proceedings of the Korean Geotechical Society Conference
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• 2002.11a
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• pp.102-117
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• 2002

The general design practice for piled footings is based on the assumption that the piles are free-standing, and that all the external loads are carried by the piles, with any contribution of the footing being ignored. This approach is not reasonable, because the footing itself is actually in direct contact with the soil, and thus carries a significant fraction of the loads. In the case of not considering the bearing capacity of footing, the bearing capacity of group piles can be evaluated conservatively in the designing the group piles. There are a number of reasons why the idea of piled raft design with considering the capacity of footing has not become widely used. One of the reasons is the lack of reliable calculation methods for estimating the behavior of piled raft. In this study the bearing capacity, settlement, load distribution, etc. of piled raft footing are studied.

• Journal of the Korean Geosynthetics Society
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• v.12 no.4
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• pp.99-107
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• 2013

In order to investigation Lateral bearing capacity of bored-precast pile, we carried out the analysis of the relationship between Lateral load and horizontal displacement using the result of horizontal pile load test. The six piles injected cement milk of 50%, 70% and 100% of the embedded length of pile were used in the horizontal pile load test. The horizontal displacement, yielding load and horizontal bearing capacity are mainly affected by The injecting ratio of cement milk (injected length of cement milk/embedded length of pile). As the injecting ratio of cement milt is increased, the starting point of horizontal displacement in piles become close to the ground surface and the amount of horizontal displacement is decreased. Also, the horizontal bearing capacity and yielding load are highly increased with increasing the ration of cement milk. The horizontal bearing capacity and yielding load of bored pile with 1 of cement milk ratio are about two or three times those of pile with 0.5 of cement milk ratio.

• Geomechanics and Engineering
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• v.24 no.1
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• pp.29-42
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• 2021

The utilization of buildings can be improved by extending them vertically. However, the added load of the extension might require building foundations to be underpinned; otherwise, the loads on the foundations might exceed their bearing capacity. In this study, a preloading method was presented aiming at transferring partial loads from existing piles to underpinning piles. A pneumatic-type model preloading device was developed and used to carry out centrifuge experiments to evaluate the load-displacement behavior of piles, the pile-soil interaction during preloading, and the additional loading caused by vertical extension. The results showed that the preloading devices effectively transfer load from existing piles to underpinning piles. In the additional loading test of group piles, the load-sharing ratio of a pile increased with its stiffness. The load-sharing ratio of a preloaded micropile was less than that of a non-preloaded micropile as a result of the reduction in axial stiffness caused by preloading before additional loading. Therefore, a slight reduction of the load-sharing capacity of an underpinning pile should be considered if the preloading method is applied. Further, two full scale preloading devices was developed. The devices preload underpinning piles and thereby produce reaction forces on a reaction frame to jack existing piles upward, thus transferring load from the existing piles to the underpinning piles. Specifically, screw-type and hydraulic-jack type devices were developed for the practical application of foundation underpinning during vertical extension, and their operability and load transfer effect verified via full-scale structural experiments.

• Journal of the Korean Geotechnical Society
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• v.18 no.4
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• pp.189-197
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• 2002

The bearing capacity of open-ended piles is affected by the degree of soil plugging, which is quantified by the incremental filling ratio, IFR. There is not at present a design criterion for open-ended piles that explicitly considers the effect of IFR on pile load capacity. In order to investigate this effect, model pile load tests using a calibration chamber were conducted on instrumented open-ended piles. The results of these tests show that the IFR can be estimated from the plug length ratio PLR, which is defined as the ratio of soil plug length to pile penetration depth. The unit base and shaft resistances decrease with increasing IFR. Based on the results of the model pile tests, new design equations for calculating base load capacity and shaft load capacity of open-ended piles are proposed.