• Journal of the Korean Geosynthetics Society
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• v.17 no.4
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• pp.41-52
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• 2018

Since the composite ground design method is easy to apply for calculation or numerical analysis, it is applied to the design of cement mixing methods. However, the comparison studies between analysis and actual results such as a trial test and construction for the cement mixing method are few because the composite ground design method was developed for the compaction pile (SCP, GCP) methods. In this study, the results of various analysis methods, such as the composite ground analysis method (1 case) and the individual pile method (3 cases), were compared with actual measurements through a two-dimensional finite element numerical analysis. In case of the surface settlements, the results of study show that the individual plate method was larger than the actual measurements, while other methods are similar. The settlements at the under ground of the improved area is overestimated in all analysis methods. When comparing numerical analysis results for the horizontal displacement, and ground reaction forces, the individual pile method in equivalent wall concept was found to be the most similar to the measurements. The composite ground method was not able to predict the behavior of stress transfer (Arching effect) and it turned out that the prediction of horizontal displacement was too large.

• Journal of the Korean Geosynthetics Society
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• v.20 no.4
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• pp.95-103
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• 2021

While the existing pile foundation had the role of supporting the superstructure or reducing the earth pressure, recently there are cases where it is integrated with the superstructure to increase the lateral resistance. This study aims to evaluate a lateral resistance of block-type breakwaters with group piles by modelling experiments. The lateral resistance and bending moments of the piles by penetrated depths for the piles were measured. As a result, it was found that the lateral resistance increased as the depth of embedment of the group piles. In particular, the lateral resistance was 1.52 times greater in the case where the pile embedded up to the riprap layer than the case where the pile was embedded into the block. For the bending moment, the rear piles ware larger than the front piles, and the outside piles were larger than the inside piles. The location of the maximum bending moment in the ground was shown at the interface between the riprap layer and the natural ground.

• Interaction and multiscale mechanics
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• v.4 no.4
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• pp.321-336
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• 2011

This paper presents the results of static vertical load tests carried out on a model building frame supported by pile groups embedded in cohesionless soil (sand). The effect of soil interaction on displacements and rotation at the column base and also the shears and bending moments in the columns of the building frame were investigated. The experimental results have been compared with those obtained from the finite element analysis and conventional method of analysis. Soil nonlinearity in the lateral direction is characterized by the p-y curves and in the axial direction by nonlinear vertical springs along the length of the piles (${\tau}-z$ curves) at their tips (Q-z curves). The results reveal that the conventional method gives the shear force in the column by about 40-60%, the bending moment at the column top about 20-30% and at the column base about 75-100% more than those from the experimental results. The response of the frame from the experimental results is in good agreement with that obtained by the nonlinear finite element analysis.

• Journal of the Korean Geotechnical Society
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• v.16 no.3
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• pp.157-162
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• 2000

측발유동을 받는 일렬 군말뚝의 그룹효과를 파악하이 위해 3차원 유한요소해석을 수행하였다. 국내의 대표적인 화강풍화토 지반에 선단지지된 말뚝을 대상으로 측방으로 지반변위 발생시 말뚝 두부조건과 중심간격(2.5D, 5.0D, 7.0D, 단독말뚝) 및 말뚝주면의 접촉효과를 고려한 군말뚝의 상호작용계수를 산정하였다. 본 연구 결과, 단독말뚝과 비교하여 군말뚝의 간격이 좁아짐에 따라 상호작용계수는 현저하게 감소하였으며 말뚝 두부조건이 회전구속, 힌지,자유단의 순으로 감소정도가 크게 나타났다. 이는 실내모형실험을 통해 산정된 상호작용계수와도 비교적 잘 일치함을 보였다.

• Proceedings of the Korean Geotechical Society Conference
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• 2003.03a
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• pp.439-446
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• 2003

In this paper the model tests have been conducted and the results are compared with those by the theoretical methods to study the behaviors of the piled raft. The size of model box is 2.2m${\times}$2m${\times}$2m. The raft is made of rigid steel plate and piles made of steel pipes. Generally the bearing capacity of group piles is designed with only the pile capacities, and the bearing capacity of raft is ignored. But the uncertainty of pile-raft-soil interaction leads to conservative design ignoring the bearing effects of raft. In the case of considering the bearing capacity of raft, the simple sum of bearing capacity of raft and that of each pile cannot be the bearing capacity of piled raft. Because the pile-raft-soil interaction affects the behavior of piled raft. Thus the effects of pile-raft-soil interaction are very important in the optimal design. In this paper, the behaviors of piled raft are studied through model tests of 2${\times}$2, 2${\times}$3, and 3${\times}$3 pile groups. The spacing between piles is changed in the model tests. And the behaviors of free standing and piled raft are also studied.

• Journal of the Korean Geotechnical Society
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• v.17 no.6
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• pp.5-14
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• 2001

This paper describes a simplified design method of stabilizing piles based on an experimental tests and an analytical study which can take into account the safety factor of slope and pile spacing. The nonlinear characteristics of the soil-pile interaction for stabilizing piles are modeled by using load transfer method. The interaction factors due to pile spacing and cap rigidity were estimated by using a three dimensional nonlinear finite element approach and laboratory tests. Based on the results obtained, the interaction factors are proposed quantitatively for one-row pile groups with spacing-to-diameter ratios varying far 2.5 to 7.0. The Bishop's simplified method of slope stability analysis is extended to incorporate the soil-pile interaction and determine the safety factor of the reinforced slope. Through the comparative study, it is found that the prediction by present approach is in relatively good agreement with the results of centrifuge tests and field tests and three dimensional finite element analyses.

• Structural Engineering and Mechanics
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• v.61 no.2
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• pp.245-253
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• 2017

The increasing lack of good quality soils allowing the development of roadway, motorway, or railway networks, as well as large scale industrial facilities, necessitates the use of reinforcement techniques. Their aim is the improvement of the global performance of compressible soils, both in terms of settlement reduction and increase of the load bearing capacity. Among the various available techniques, the improvement of soils by incorporating vertical stiff piles appears to be a particularly appropriate solution, since it is easy to implement and does not require any substitution of significant soft soil volumes. The technique consists in driving a group of regularly spaced piles through a soft soil layer down to an underlying competent substratum. The surface load being thus transferred to this substratum by means of those reinforcing piles, which illustrates the case of a piled embankment. The differential settlements at the base of the embankment between the soft soil and the stiff piles lead to an "arching effect" in the embankment due to shearing mechanisms. This effect, which can be accentuated by the use of large pile caps, allows partial load transfer onto the pile, as well as surface settlement reduction, thus ensuring that the surface structure works properly. A technique for producing rigid piles has been developed to achieve in a single operation a rigid circular pile associated with a cone shaped head reversed on the place of a rigid circular pile. This technique has been used with success in a pile-supported road near Bourgoin-Jallieu (France). In this article, a numerical study based on this real case is proposed to highlight the functioning mode of this new technique in the case of industrial slabs.

• Journal of the Korean Geotechnical Society
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• v.32 no.8
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• pp.35-46
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• 2016

In this study, a sensitivity analysis was carried out by using numerical analysis under the consideration that it is difficult to analyze the behavior of real piled raft foundations on different ground conditions through a real scale test. The program used for numerical analysis is FLAC 3D based on the finite difference method. Piles were modelled by using pile element that is one of the structure elements of FLAC 3D and the ground and raft were modelled by using continuum element. With a fixed pile arrangement of $3{\times}3$, the diameter, length, space of piles, and ground conditions were selected as sensitivity parameters and their mutual correlation were investigated. As a result, the bigger and longer pile diameter, length and pile space are, the bigger the bearing capacity of the piled raft becomes. When pile space exceeded a specific value, however, the piled raft foundation behaved like a shallow foundation supported by only a raft. Also it can be confirmed that the better ground conditions are, the more total bearing capacity of the piled raft foundation increases.

• Land and Housing Review
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• v.3 no.4
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• pp.451-456
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• 2012

In this study, a numerical analysis to evaluate the reduction of seismic load due to pile group was performed and compared the peak ground acceleration(PGA) measured at free-field and foundation. The special attention was given to the amplification of seismic acceleration on the foundation due to the pile effects. The analysis considering pile effects was carried out for 4, 8 and 12 piles with same condition by PLAXIS 2D Dynamics. Based on the analysis results, it is found that the overall reduction in seismic load due to foundation and reduction rates are similar irrespective of pile numbers. This study gives a possibility for effective design of piled foundation by reducing seismic load about 20~25%.

• Proceedings of the Korean Geotechical Society Conference
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• 2002.10a
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• pp.358-365
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• 2002

In this paper the model tests have been conducted and the results were compared with those by the theoretical methods to study the behaviors of the piled raft. The size of model box is 2.2m${\times}$2m${\times}$2m. The raft is made of rigid steel plate and piles are made of steel pipes. Generally the bearing capacity of group piles is designed with only the pile capacities, which is Ignored the bearing capacity of raft. But the uncertainty of pile-raft-soil interaction leads to conservative design ignoring the bearing effects of raft. In the case of considering the bearing capacity of raft, the simple sum of bearing capacity of raft and that of each pile cannot be the bearing capacity of piled raft. Because the pile-raft-soil interaction affects the behavior of piled raft. Thus the effects of pile-raft-soil interaction are very important in the optimal design. In this paper, the behaviors of piled raft are studied through model tests of 2${\times}$2, 2${\times}$3, and 3${\times}$3 pile groups. The spacing between piles is changed in the model tests. And the behaviors of free standing and piled raft are also studied.