• Proceedings of the Korean Geotechical Society Conference
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• 2008.10a
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• pp.407-426
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• 2008

The bentonite slurry has been used as the stabilize suspension for wet process bored pile construction in Thailand. The bentonite suspension has benefit on filtration in the sand layer, but it creates thick cake film along pile shaft and loose sedimentation at pile toe. The base grouting technique was widely used to rectify the soft base or loose sedimentation problem of bored pile. The base grouting technique was not increased only end bearing capacity, but was also more increase in skin friction capacity of the bored piles. The comprehensive researches on base grouting was carried out by installing PVC casing inside the shaft to allow the drilling through the pile base in order to collect the soil sample below the pile tip. The polymer based slurry recently was used to replace the bentonite slurry to overcome the thick cake film along pile shaft as well as loose sedimentation at pile toe. The extent research on polymer slurry by physical model was performed to verify the real behavior of polymer. The appropriate mixing ratio of polymer was proposed. The design skin friction coefficient, $\beta$ and end bearing coefficient, Nq, for sand layer base on fully instrumented tested pile were proposed. The application on remedial of the lose capacity bored pile with large displacement in Bangladesh was proposed and discussed.

• Coupled systems mechanics
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• v.1 no.1
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• pp.1-7
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• 2012

The problem of laterally loaded piles is particularly a complex soil-structure interaction problem. The flexural stresses developed due to the combined action of axial load and bending moment must be evaluated in a realistic and rational manner for safe and economical design of pile foundation. The paper reports the finite element analysis of pile groups. For this purpose simplified models along the lines similar to that suggested by Desai et al. (1981) are used for idealizing various elements of the foundation system. The pile is idealized one dimensional beam element, pile cap as two dimensional plate element and the soil as independent closely spaced linearly elastic springs. The analysis takes into consideration the effect of interaction between pile cap and soil underlying it. The pile group is considered to have been embedded in cohesive soil. The parametric study is carried out to examine the effect of pile spacing, pile diameter, number of piles and arrangement of pile on the responses of pile group. The responses considered include the displacement at top of pile group and bending moment in piles. The results obtained using the simplified approach of the F.E. analysis are further compared with the results of the complete 3-D F.E. analysis published earlier and fair agreement is observed in the either result.

• Geomechanics and Engineering
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• v.17 no.3
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• pp.287-294
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• 2019

The finite element method (FEM) is widely used to evaluate the seismic performance of pile-supported buildings. However, there are problems associated with modeling the pile end resistance using the FEM, such as the dependence on the mesh size. This paper proposes a new method of modeling around the pile tip to avoid the mesh size effect in two-dimensional (2D) analyses. Specifically, we consider the area of influence around the pile tip as an artificial constraint on the behavior of the soil. We explain the problems with existing methods of modeling the pile tip. We then conduct a three-dimensional (3D) analysis of a pile in various soil conditions to evaluate the area of influence of the soil around the pile tip. The analysis results show that the normalized area of influence extends approximately 2.5 times the diameter of the pile below the pile tip. Finally, we propose a new method for modeling pile foundations with artificial constraints on the nodal points within the area of influence. The proposed model is expected to be useful in the practical seismic design of pile-supported buildings via a 2D analysis.

• International Journal of High-Rise Buildings
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• v.4 no.4
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• pp.271-281
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• 2015

This paper introduces detailed three-dimensional numerical analyses on a bored pile foundation for a high-rise building. A static load test was performed on a test pile and a numerical model of a single pile, which was calibrated by comparing it with the test result. The detailed numerical analysis was then conducted on the entire high-rise building foundation. Further study focused on soil pressures under the base slab of a piled raft foundation. Total seven cases with different pile numbers and raft-soil contact conditions were investigated. The design criteria of a foundation, especially settlement requirement were satisfied even for the cases with fewer piles under considerable soil pressure beneath the base slab. The bending moment for the structural design of the base slab was reduced by incorporating soil pressures beneath the base slab along with bored piles. Through the comparative studies, it was found that a more efficient design can be achieved by considering the soil pressure beneath the slab.

• Geomechanics and Engineering
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• v.11 no.2
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• pp.309-323
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• 2016

As the forefront of structural design method, capacity spectrum method can be applied conveniently, and through this method, deformation demand of structure can be considered. However, there is no research for the seismic application in the structure of sheet pile retaining wall to report. Therefore, focusing on laterally loaded stabilizing sheet pile wall, which belongs to flexible cantilever retaining structure and meets the applying requirement of capacity spectrum method from seismic design of building structure, this paper studied an approach of seismic design of sheet pile wall based on capacity spectrum method. In the procedure, the interaction between soil and structure was simplified, and through Pushover analysis, seismic fortification standard was well associated with performance of retaining structure. In addition, by comparing the result of nonlinear time history analysis, it suggests that this approach is applicable.

• Journal of the Korean Geotechnical Society
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• v.35 no.9
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• pp.29-36
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• 2019

Axial compressive failure loads ($P_n$) of diameter 500 mm and diameter 600 mm A type PHC pile were calculated as 7.7 MN and 10.6 MN, respectively. In the static pile load tests, the maximum axial compressive loads of the above 2 kinds of A type pile were measured as 6.9 MN and 8.8 MN respectively, therefore these measured maximum loads were at the level of 90% and 83% of $P_n$ respectively. Long-term allowable axial compressive loads ($P_a$) of the above 2 kinds of A type pile were 1.7 MN and 2.3 MN respectively. From the bi-directional pile load test data on the prebored PHC piles, it was confirmed that the allowable axial compressive bearing resistance was estimated as 131% of the long-term allowable compressive load of the PHC pile and showed higher than the allowable bearing capacity calculated by the current design method. Therefore, it has been verified that the PHC pile can be used up to the maximum long-term allowable compressive load, and it is suggested that the ultimate pile capacity formula used in the current design for prebored PHC piles should be improved to accommodate the actual capacity.

• Journal of the Korean Society of Hazard Mitigation
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• v.1 no.3 s.3
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• pp.103-110
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• 2001

The objective of this study is to investigate the behavior of superstructure considering several factors such as change of pile rigidity, soil characteristics, and the constraint condition of support. The results of this study are as follows: 1. Pile-rigidity computed by the rotating deformed plane method is continuously varied up to approximately 5D(D=diameter of pile) below the ground level. This result is consistent with the previous study$^{(12)}$, in which the pile deformation occurs at approximately $3{\sim}6$ times of pile diameter from the ground level. 2. For bridge structure-pile system, analytical results of internal forces and deformations show different values for modified pile rigidity and unchanged pile rigidity. 3. Detaild analysis considering modified pile rigidity is required for the long-span bridge design with structure pile system.

• Journal of the Korean GEO-environmental Society
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• v.19 no.7
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• pp.5-11
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• 2018

Instead of a single pile, group piles are usually used for the pile foundation. If the earthquake occurs in the ground where group piles are installed, dynamic behavior of group piles are affected not only by interaction of piles and the ground movement but also by the pile cap. However, in Korea, the pile cap influence is not taken account into the design of group piles. Research on dynamic behavior of group piles has been performed only to verify interaction of piles and the ground and has not considered the pile cap as a factor. In this research, 1g shaking table model tests were performed to verify the thickness of the pile cap affects dynamic behavior of group piles that were installed in the ground where the earthquake would occur. The test results show that, as thickness of the pile cap increased, acceleration and horizontal displacement of the pile cap decreasd while vertical displacement of the pile cap increased. The results also showed that, among the group files tested, acceleration, horizontal displacement, and vertical displacement of the bearing pile are smaller than those of the friction pile.

• Journal of the Korean Geotechnical Society
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• v.27 no.5
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• pp.33-43
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• 2011

In this study, simplified analysis (discrete analysis of column and pile) of pile bent structures was performed on the basis of the equivalent base spring model. And the minimum reinforcement ratio in pile bent structures was evaluated by taking into account various factors. To obtain the detailed information, simplified analysis was performed for column-pile interactions and the behavior of a column-pile was estimated and highlighted. Based on this study, it is shown that previous design method based on virtual fixed point theory cannot adequately predict the physical behavior of pile bent structures. It is found that the maximum bending moment is located within craking moment of the pile when material non-linearity is considered. It is also found that the minimum reinforcement ratio (=0.4%) is appropriately applicable for the optimal design of pile bent structure under ultimate lateral loading.

• Geotechnical Engineering
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• v.8 no.2
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• pp.21-30
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• 1992

Though the pile skin friction can take substantial amount of load carrying capacity, it has often been ignored in the design. Even when the pile skin friction is taken into consideration, it is questionable about the reliability of estimating it. It has been even worse in Korea. since in most cases the available information is only the SPT N values and not much information has been known about the correlation between N value and the pile skin friction in residual soils. With SPLT (Simple Pile Loading Test) it is possible to measure the pile skin friction separately from the tip resistance. In this research, results of the measured pile skin friction in residual soils are analysed. And a new design correlation based on SPT N value is proposed.