• Journal of the Korean Geotechnical Society
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• v.19 no.1
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• pp.31-40
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• 2003

Current design of pile group is based on the estimation of the overall bearing capacity of a pile group from that of a single pile using a group efficiency. However, the behaviors of a pile group are influenced by various factors such as the method of pile installation, pile-soil-pile interaction, cap-soil-pile interaction, etc. Thus, it is practically impossible to take into account these factors reasonably with the only group efficiency. In this paper, a new method for the design of pile groups is proposed, where the significant factors affecting the behavior of a pile group are considered separately by adopting several efficiencies. Furthermore, in the proposed method, the load transfer characteristics of piles and the difference of pile behaviors with respect to the pile locations in group can be taken into account. The efficiencies for the method are determined using the settlement failure criterion, which is consistent with the concept of allowable settlement fur structures. The efficiencies calculated from the results of existing model tests are presented, and the bearing capacity of a pile group in the other model test is calculated and compared with that from the test result to verify the validity of the proposed method.

• Journal of the Korean Geotechnical Society
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• v.21 no.5
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• pp.51-58
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• 2005

In this study, the large scale model tests were executed to estimate the Load Sharing Ratio (LSR) of raft in a piled footing under various conditions. The conditions such as the subsoil type, pile length, pile spacing, away type and pile installation method etc. were varied in the pile loading tests about the free-standing group piles and a piled footing. As a result of this study, it was found that there was no difference in the load-settlement curves, resulting from the pile installation method and subsoil type. The piles supported most of the external load until a yielding load of the piled footing, but the raft supported a considerable load after a yielding load. As the relative density of sands increased, the LSR decreased. As the pile spacing was wider and the pile length increased, there was a tendancy for the LSR to increase. But it was also found that the LSR was not affected by the pile installation method and the subsoil type.

• Journal of the Korean GEO-environmental Society
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• v.20 no.10
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• pp.39-46
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• 2019

The interaction between the ground and structures should be considered for seismic design of group piles supporting the superstructure. The p-y curve has been used widely for the analysis of nonlinear relationship between the ground and structures, and various researches have conducted to apply the dynamic p-y curve for seismic design of group piles. This curve considers the interaction between the ground and structures under the dynamic load such as an earthquake. However the supported effect by the pile cap and the interaction by inertia behavior of superstructures. Therefore, the shaking table test was conducted to verify the effect of the change of the pile cap in group piles supporting superstructures embedded in sandy soil. The test condition is that the arrangement and distance between centers of piles are fixed and the length of the pile cap is changed for various distances between the pile cap side and the pile center. The result shows that the distance between the pile cap side and the pile center have an effect on the dynamic p-y curve and the effect of group piles.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.32 no.2C
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• pp.49-60
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• 2012

In this study, the behaviors of friction pile groups are investigated using 3D finite element (FE) analysis. The emphasis was quantifying on the shear load transfer (f-w) characteristics of pile groups and the shaft group effects. A framework for determining the f-w curve is proposed based on both theoretical analysis and field load test database. Through comparisons with case histories and FE results, it is shown that the proposed f-w curve is capable of predicting the behavior of a friction pile in deep soft clay. Additionally, a numerical analysis that takes into account the group efficiency factors were performed for major parameter on group pile-soil interaction, such as the pile spacing, pile arrangement, soil condition, and location of pile cap. Based on these results, the shaft group efficiency factors were also proposed.

• Proceedings of the ESK Conference
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• 1994.04a
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• pp.105-105
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• 1994

신체 부위를 이용한 Manual Materials handling(MMH) 작업시 무리한 작업하중의 취급으로 인하 여 많은 사고 또는 요통이 발생하기 때문에 작업자의 능력에 맞는 적정 하중에 대한 연구가 필요 하다. MMH작업의 적정하중에관한 연구는 미국 등의 나라에서는 많이 이루어져 왔으나 우리나라에서 는 연구되어 있지 않다. 미국의 경우 NIOSH Guideline을 만들어 MMH시 작업지침으로 활용하고 있으 나 이 지침을 그대로 우리나라에 적용하기에는 신체조건이 달라 우리나라 고유의 연구가 필요하겠다. 적정하중의 연구에는 많은 시간과 경비가 필요하기 때문에 외국의 경우 심리 육체적방법(Psychophysical Method)을 사용하여 시간과 경비를 줄이고도 실제 8시간 작업시의 결과와 비슷한 결과를 얻었다. 본 연구에서는 MMH작업의 적정 하중결정에 있어서 심리육체적 방법을 사용하여 한국인 작업자에 대한 하중과 HIOSH Guideline의 RWL값과의 비교를 하였다. 학생군과 실제 작업자군의 피실험자에 대하여 심리육체적 방법을 적용하여 들기작업을 실험하였다. 6가지 들기 작업을 20분 동안 실시하여 피실험자들이 자신에게 적합하다고 생각하는 적정하중을 측정하였다. 그 결과, 학생군은 RWL값보다 평균 2.5배를, 작업자군은 3.4 배를 적정하중으로 정하였다. 따라서 HIOSH Guideline을 적용한 RWL값은 우리나라 작업자에게는 많은 여유가 있는 하중임을 보여 주었다.

• Journal of the Korean Geotechnical Society
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• v.28 no.9
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• pp.57-67
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• 2012

In the design for piled rafts, the load capacity of the raft is in general ignored and the load capacities of pile are only considered for the estimation of the total load carrying capacity of the piled raft. The axial resistance of piled raft is offered by the raft and group piles acting on the same supporting ground soils. As a consequence, pile - soil - raft and pile - soil interactions, occurring by stress and displacement duplication with pile and raft loading conditions, acts as a key element in the design for piled rafts. In this study, a series of centrifuge model tests has been performed to compare the axial behavior of group pile and raft with that of a piled raft (having 16 component piles with an array of $4{\times}4$) at the stiff and soft clays. From the test results, it is observed that the interactions of piles, soil, and raft has little influences on the load capacities of piles and raft in piled rafts compared with the load capacities of group piles and raft at the same clay soil condition.

• Journal of the Korean GEO-environmental Society
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• v.8 no.3
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• pp.67-75
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• 2007

This study was undertaken in order to investigate the load bearing capacity of raft in a piled raft through the laboratory model tests, the numerical and analytical analyses. The model tests were conducted about a piled raft, the free-standing pile group, a single pile, as well as a shallow foundation under equal conditions. The pile spacing and length, group type and soil conditions were varied in the laboratory model tests. The experimental results were compared with those by the commercial program, DEFPIG, conventional methods and Phung's method. According to this study, the behavior of piled raft was affected by pile spacing, length and soil conditions. Phung's method proved to be reliable for estimating the experimental results.

• Journal of the Korean Geotechnical Society
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• v.21 no.10
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• pp.123-131
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• 2005

In the present study, laboratory pull-out tests with screw anchors are carried out to investigate behavior characteristics of the anchors used in foundation system of underground structures which are applied to uplifting seepage forces. Small scaled pull-out tests in sand under saturated condition and dry condition were carried out. For estimating the group effects of the anchors, the upward displacement and the pullout load varied with spacing of the anchor were observed. The test results were compared with theoretical equation for the ultimate pull-out force. Also, the result of tests can be used to the finite element analysis program, $PENTAGON^{2D}$.

• Journal of the Korean Geotechnical Society
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• v.35 no.11
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• pp.25-36
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• 2019

The safety barrier is installed on road embankment to prevent vehicles from falling into road side slope. Among the safety barrier, flexible guardrails are usually installed. The flexible guardrail generally consists of a protection cross-beam and supporting in-line piles. These guardrail piles are installed nearby slope edge of road embankment because the side area of the road is much narrow. The protection cross-beam absorbs impact energy caused by vehicle collision. The pile-soil interaction also absorbs the rest of the impact energy and then, finally, the flexible guardrail system resists the impact load. This paper aims to investigate the pile-soil interaction subjected to impact load using centrifuge model tests. In this study, a single pile was installed in compacted residual soil and loaded under lateral impact load. An impact loading system was designed and developed available on centrifuge tests. Using this loading system, a parametric study was performed and the parameters include types of loading and ground. Finally, the ultimate bearing capacity of supporting pile under impact load was analyzed using load-displacement curve and soil reaction pressure distributions at ultimate were evaluated and compared with previous studies.

• Journal of the Korean GEO-environmental Society
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• v.19 no.10
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• pp.35-41
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• 2018

Dynamic interaction of the ground-foundation-structure must be considered for safety of earthquake resistant design for piles supported structures. The p-y curve, which is proposed in the static load and cyclic load cases, is used for the earthquake resistant design of piles. The p-y curve does not consider dynamic interaction of the ground-foundation-structure on dynamic load cases such as earthquake. Therefore, it is difficult to apply the p-y curve to earthquake resistant design. The dynamic p-y curve by considering dynamic interaction of the ground-foundation-structure has been studied, and researches had same conditions that pile caps were on the ground surface and superstructures were added on pile caps for the simple weight. However, group piles are normally embedded into the ground except for marine structures, so it seems that the embedding the pile cap influences on the dynamic p-y curve of group piles. In this study, the shaking table model test was conducted to confirm dynamic behavior of group piles by the embedded pile cap in the ground. The result showed that dynamic behavior was different between two cases by embedding the pile cap or not.