• Title/Summary/Keyword: Isolated pile cap

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A Study on the Effect of Carrying Vertical Loads Over Embankment Piles (성토지지말뚝의 연직하중 분담효과에 관한 연구)

  • 홍원표;이광우
    • Journal of the Korean Geotechnical Society
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    • v.18 no.4
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    • pp.285-294
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    • 2002
  • Embankment Piles, which is subjected to damage due to lateral movement of soft ground, can be classified into pile slab, cap beam pile, and isolated cap pile according to the installation pattern of pile cap. In the cap beam pile and the isolated cap pile method, the soil arch is developed by the different stiffness between pile and soil, and most embankment loads are transferred into embankment piles through soil arch. In these two methods, the difference of soil arch is that the soil arch of the cap beam pile method develops like the arch from of tunnel between cap beams and the soil arch of the isolated cap pile method develops like dome between isolated caps. Therefore, theoretical analysis methods on soil arching effect of the cap beam pile and the isolated cap pile method were respectively proposed according to their own arch form considering the limiting equilibrium of stresses in a crown of soil arch. And a series of model tests were performed both to investigate the load transfer by soil arching in fills above embankment piles and to verify the reliability of the theoretical analysis.

The Influence of Negative Skin Friction on Piles in Groups Connected to a Cap (부마찰력이 작용하는 기초판으로 연결된 군말뚝의 거동)

  • Lee, Cheol-Ju;Park, Byung-Soo
    • Journal of the Korean Geotechnical Society
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    • v.22 no.8
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    • pp.25-31
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    • 2006
  • Over the years the investigation of behaviour of piles in groups connected to a cap in consolidating soil has attracted far less attention than the study of isolated piles in groups. In this paper, a series of three-dimensional numerical simulations have been performed to study the behaviour of pile groups connected to a cap in consolidating ground. Both elastic no-slip and elasto-plastic slip analyses were considered. Based on the analysis results, when piles were connected to a cap, tensile forces were developed near the pile head at the outer piles. Elastic solution and no-slip analysis over-predicted the tensile force near the pile head for outer piles. Relatively speaking, the number of piles in a group is more important than the pile spacing in terms of the influence of negative skin friction on the pile behaviour. The issue on the development of tensile forces on the pile head at the outer piles is perhaps needed to be carefully considered in the pile design to prevent the damages of the pile-cap connection.

Model Tests on Embankment Piles with Isolated Pile Caps (단독캡을 사용한 성토지지말뚝에 대한 모형실험)

  • 홍원표;이광우
    • Journal of the Korean Geotechnical Society
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    • v.19 no.6
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    • pp.49-59
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    • 2003
  • The factors affecting the vertical loads acting on embankment piles can be classified into two factors on pile and soil. Factor on pile is the space between pile cap and factors on soil are embankment height and soil parameters(c, $\phi$). Therefore, a series of model tests were performed both to investigate the extent of influence of these factors and to verify the reliability of the proposed theoretical analysis. In the model tests, the piles were installed in the 6 columns $\times$ 6 rows(or 5 columns $\times$ 5 rows) below the embankment and the isolated pile caps with the area of 2.5cm $\times$ 2.5cm were installed on each pile head. The portion of the embankment load carried by model pile caps decreases with increment of the space between pile caps and increases with increment of the embankment height and the relative density(or internal friction angle) of fill. Also, the experimental results showed good agreement with theoretical predictions.

Soil Arching in Embarikments Suppoyed by Piles with Geosynthethics (말뚝과 토목섬유로 지지된 성토지반의 아칭효과)

  • Hong, Won-Pyo;Lee, Jae-Ho
    • Journal of the Korean Geotechnical Society
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    • v.23 no.6
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    • pp.53-66
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    • 2007
  • A series of model tests were performed to investigate the soil arching effect in embankments supported by piles with geosynthetics. In the model tests, model piles with isolated cap were inserted through the holes in a steel plate, which could be operated up and down. Then geosynthetics was laid on the pile caps below sand fills. The settlement of soft ground was simulated by lowering the plate. As the plate was lowered, the soil arching was mobilized in the embankments. The deformation of both the sand fills and geosynthetics were captured by camera. Also the loads acting on pile cap and the tensile strain of geosynthetics were monitored by data logging system. Model tests showed that the embankment loads transferred on pile cap by soil arching Increased rapidly with settlement of the soft ground. In case of the absence of geosynthetics, the loads acting on pile caps dropped to residual value after peak value, whereas loads on pile caps gradually increased until constant value in case of geosynthetic-reinforced. This illustrated that reinforcing with the geosynthetics has a good effect to restrain the settlement of embankments. Also, the deformation shape of geosynthetics between pile caps was circular. The embankment loads transferred on pile caps can be estimated by considering both soil arching and tensile strain of geosynthetics in embankments supported by piles with geosynthetics.

Analytical model of isolated bridges considering soil-pile-structure interaction for moderate earthquakes

  • Mohammad Shamsi;Ehsan Moshtagh;Amir H. Vakili
    • Geomechanics and Engineering
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    • v.34 no.5
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    • pp.529-545
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    • 2023
  • The coupled soil-pile-structure seismic response is recently in the spotlight of researchers because of its extensive applications in the different fields of engineering such as bridges, offshore platforms, wind turbines, and buildings. In this paper, a simple analytical model is developed to evaluate the dynamic performance of seismically isolated bridges considering triple interactions of soil, piles, and bridges simultaneously. Novel expressions are proposed to present the dynamic behavior of pile groups in inhomogeneous soils with various shear modulus along with depth. Both cohesive and cohesionless soil deposits can be simulated by this analytical model with a generalized function of varied shear modulus along the soil depth belonging to an inhomogeneous stratum. The methodology is discussed in detail and validated by rigorous dynamic solution of 3D continuum modeling, and time history analysis of centrifuge tests. The proposed analytical model accuracy is guaranteed by the acceptable agreement between the experimental/numerical and analytical results. A comparison of the proposed linear model results with nonlinear centrifuge tests showed that during moderate (frequent) earthquakes the relative differences in responses of the superstructure and the pile cap can be ignored. However, during strong excitations, the response calculated in the linear time history analysis is always lower than the real conditions with the nonlinear behavior of the soil-pile-bridge system. The current simple and efficient method provides the accuracy and the least computational costs in comparison to the full three-dimensional analyses.

Laboratory Model Tests on the Load Transfer in Geosynthetic-Reinforced and Pile-Supported Embankment System (토목섬유보강 성토지지말뚝시스템에서의 하중전이 효과에 관한 모형실험)

  • Hong, Won-Pyo;Lee, Jae-Ho
    • Journal of the Korean Geosynthetics Society
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    • v.9 no.3
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    • pp.9-18
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    • 2010
  • A series of model tests were performed to investigate the load transfer by soil arching in geosynthetic-reinforced and pile-supported(GRPS) embankment systems. In the model tests, model piles with isolated cap were inserted in the model container and geosynthetics was laid on the pile caps below sand fills. The settlement of soft ground was simulated by rubber form. The loads acting on pile caps and the tensile strain of geosynthetics were monitored by data logging system. At the given interval ratio of pile caps, the efficiency in GRPS embankment systems increased with increasing the height of embankment fills, then gradually converged at constant value. Also, at the given height of embankment fills, the efficiency decreased with increasing the pile spacing. The embankment loads transferred on pile cap by soil arching increased when the geosynthetics installed with piles. This illustrated that reinforcing with the geosynthetics have a good effect to restraint the movement of surrounding soft grounds. The load transfer in GRPS embankment systems was affected by the interval ratio, height of fills, properties of grounds and tensile stiffness and so on.

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