• 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.

• 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.

• Journal of the Korean Geotechnical Society
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• v.21 no.1
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• pp.69-80
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• 2005

In order to investigate the stabilizing effect of piles against sliding, a series of model tests were carried out. The model apparatus was designed to perform the model test of slope reinforced by stabilizing piles. The instrumentation system was used to measure the deflection of stabilizing piles during slope failure. The stabilizing effect of the piles in a row with some interval ratio is larger than the isolated pile without interval ratio. Because the prevention force of piles in a row increased due to the soil arching effect between piles during slope failure. Especially, the maximum value of prevention ratio was presented at 0.5 of interval ratio. If the required prevention ratio is 1.1, the interval ratio must be installed from 0.5 to 0.8. Also, the stabilizing effect of piles against sliding is excellent at the interval ratio between 0.5 and 0.8. This value can be proposed as the criterion of the interval ratio between piles against slope failure.

• Geomechanics and Engineering
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• v.39 no.3
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• pp.227-240
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• 2024

This study investigates the control effect of isolation piles on ground settlement resulting from foundation pit excavation. Based on the three-stage analysis method, first, the Kerr three-parameter foundation model is introduced, and the deflection differential equation is derived to solve the horizontal displacement of the diaphragm wall. Then, based on the horizontal displacement of the diaphragm wall, the boundary element method is used to calculate the additional stress at the boundary of the foundation pit, and the horizontal additional displacement and additional stress of the soil free field at the position of the isolation pile are obtained using the Mindlin solution. Subsequently, soil free field additional stress is applied to the pile foundation, and the shielding effect of group piles is also considered. Based on the Kerr three-parameter foundation model, the deflection differential equation of the pile foundation under the influence of horizontally oriented additional stress is established to solve the horizontal displacement of the isolated piles. Finally, the boundary element method is used again to invert the additional stress caused by the horizontal displacement of the isolation pile, and the surface settlement after the isolation pile is calculated in combination with the Mindlin vertical displacement solution. The spatial finite element model is established and compared with the theoretical calculation results to prove the rationality of the theory. The influence of basic construction parameters is analyzed theoretically, and it is found that the surface settlement is reduced by 30.9% compared with no isolation pile. Of the selected parameters in this paper, the effects of the isolation pile's controlled diameter, spacing, and elastic modulus, the thickness and elastic modulus of the diaphragm wall on the surface settlement are 4.9 mm, 3.1 mm, 3.3 mm, 3 mm, 1.7 mm, respectively, which are 45.4%, 28.7%, 30.6%, 27.8%, 15.7% of the standard working conditions, respectively. This shows that optimization of the isolation pile parameters has the best effect on surface settlement, optimization of the diaphragm wall parameters has the poor effect.

• 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.

• 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.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.30 no.1C
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• pp.27-35
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• 2010

Instrumented steel sheet piles being driven by vibratory pile driver were installed in granular soil deposit and behaviors of the sheet piles were investigated. One of the instrumented steel sheet pile was installed without clutch and the other was installed with clutch. Sheet pile with clutch means that of installed in connection with pre-installed sheet pile. Penetration rates of sheet piles measured from depth measuring drum has shown that interlock friction had great effect on penetration speed of sheet pile. Clutch friction shows irregular distribution along the depths of penetration and its magnitude was estimated as 19.1kN/m. According to the accelerations obtained from accelerometer, it was seen that steel sheet pile behaviored nearly as a rigid body. Efficiency factor of an isolated sheet pile was 0.42 and that of the connected sheet pile was 0.71. Shapes of dynamic load transfer curves obtained from analysis of measuring devices was similar to those suggested by Dierssen.

• Earthquakes and Structures
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• v.23 no.6
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• pp.517-526
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• 2022

Previous studies have shown that pile-soil interactions have significant influences on the isolation efficiency of an isolated structure. However, most of the existing tests were carried out using a 1-g shaking table, which cannot reproduce the soil stresses resulting in distortion of the simulated pile-soil interactions. In this study, a centrifuge shaking table modelling of the seismic responses of a friction pendulum bearing isolated structure with a pile foundation under earthquakes were conducted. The pile foundation structure was designed and constructed with a scale factor of 1:100. Two layers of the foundation soil, i.e., the bottom layer was made of plaster and the upper layer was normal soil, were carefully prepared to meet the similitude requirement. Seismic responses, including strains, displacement, acceleration, and soil pressure were collected. The settlement of the soil, sliding of the isolator, dynamic amplification factor and bending moment of the piles were analysed to reveal the influence of the soil structure interaction on the seismic performance of the structure. It is found that the soil rotates significantly under earthquake motions and the peak rotation is about 0.021 degree under 24.0 g motions. The isolator cannot return to the initial position after the tests because of the unrecoverable deformation of the soil and the friction between the curved surface of the slider and the concave plate.

• 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.

• 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.