• Journal of the Korean Geotechnical Society
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• v.34 no.7
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• pp.29-38
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• 2018

Three-dimensional continuum modeling of dynamic soil-pile-structure interaction embedded in a liquefiable sand was carried out. Finn model which can model liquefaction behavior using effective stress method was adopted to simulate development of pore water pressure according to shear deformation of soil directly in real time. Finn model was incorporated into Non-linear elastic, Mohr-Coulomb plastic model. Calibration of proposed modeling method was performed by comparing the results with those of the centrifuge tests performed by Wilson (1998). Excess pore pressure ratio, pile bending moment, pile head displacement-time history according to depth calculated by numerical analysis agreed reasonably well with the test results. Validation of the proposed modeling method was later performed using another test case, and good agreement between the computed and measured values was observed.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.12 no.12
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• pp.5963-5973
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• 2011

Current design and analyzing methods about soil nailing structures, developed on the basis of results obtained from experiments in laboratory or in field and numerical analyses, have applied different interaction mechanisms between the reinforced nails and the surrounding ground, and different safety factors against failure have been obtained. They might be proper approaches if the assumptions about rigidity of nails and ground conditions are met with actual conditions occurred in field. Otherwise, they would result in designing on analyzing in inappropriate ways so that it is needed to evaluate the validity of them. Therefore, in this research using the Centrifugal Model Testing, numerical parameters experiments about soil nailing structures' behavior and failure mechanism were performed. In the numerical parameters experiments, transmuted nail's length, setting angle, nail's front panel, stiffness variously, and increased the level of gravity until wall model was destroyed. Based on experimental results, we compared the effect, failure mechanism caused from parameters changes. By reviewing and comparing centrifugal model test results and methods currently in use, verified validity of existing methods.

• Journal of the Korean Geotechnical Society
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• v.18 no.6
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• pp.141-152
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• 2002

This paper is the result of the experimental and numerical research on the distribution of vertical earth pressure due to surcharge loads acting on cantilever retaining wall close to a rigid slope with a stiff angle. Centrifuge model experiments were performed with changing the roughness of adjacent slope to the wall, distance between the wall and the slope and gravitational levels. Vertical earth pressures were measured by earth cells embedded in the backfill of the wall. Test results of vertical earth pressures due to surcharge loads were compared with theoretical estimations by using two different methods of limit equilibrium and the numerical analysis. For limit equilibrium methods, the modified silo and the wedge theories, proposed by Chung(1993, 1997), were used to analyze test results. Based on those modified theories, the particular solution with the boundary condition of surcharge loads on the surface of backfill was obtained to find the vertical stress distributions acting on the backfill. FLAC with the hyperbolic constitutive model was also used for the numerical estimation. As a result of comparison of test results with theoretical and numerical estimations, distribution of vertical earth pressures obtained from centrifuge model tests is generally in good agreement with numerical estmated values by using FLAC whereas the wedge theory shows values close to test results in case the distance between the wall and the slope is narrow.

• Journal of the Korean Geotechnical Society
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• v.28 no.10
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• pp.27-40
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• 2012

In the design of a piled raft, the axial resistance 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, act as a key element changing resistances of the raft and group piles. In this study, a series of centrifuge model tests have 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 $4{\times}4$) in sands with different relative densities. The test results revealed that the increase of settlement resistance occurs separately with settlement by group pile - soil interactions. The axial resistance of group piles (at piled raft) increases by group pile - raft (pile cap) interactions and that of raft (at piled raft) decreases by group pile - raft (pile cap) interactions.

• Journal of the Korea institute for structural maintenance and inspection
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• v.15 no.3
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• pp.99-105
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• 2011

When a certain magnitude earthquake occurs, serious damage for human and properties is a major concern for most of the subway stations which were not applied for earthquake resistant design. Consideration and experimental verification for ground and structural behavior based on soil-structure interaction relation are required to evaluate seismic performance of the subway station as embedded structures. For 1/60 scaled subway station model, centrifuge modeling shaking table test is performed using Kobe and Northridge earthquakes. Compare to displacements and moments of the underground and structure obtained by soil response analysis and response displacement method based on experimental results, this paper shows how to evaluate seismic performance of subway station.

• Journal of the Korean Geotechnical Society
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• v.22 no.1
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• pp.53-61
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• 2006

Soil liquefaction occurs by complex dynamic interaction between soil particles and pore fluid. Therefore, experimental researches have been widely performed to analyze liquefaction phenomena. In this research, centrifuge tests were performed to analyze the liquefaction behavior of horizontal sand ground. Centrifugal acceleration was 40g and the thickness of model ground was 25cm, which simulates 10m thickness in prototype scale. Viscous fluid was used as pore fluid to remove the time scaling difference between dissipation and dynamic shaking. Test results showed that the dissipation of excess pore pressure is the combined behavior of solidification and consolidation. In addition, the solidification rate, the ground acceleration amplitude, and the dynamic permeability during solidification were influenced by the confining pressure.

• Journal of the Korean Geotechnical Society
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• v.21 no.1
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• pp.81-91
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• 2005

This paper is the results of experimental and numerical works on the investigating design factors influencing the bearing capacity, the ratio of stress concentration, and the failure mechanism of the clay ground improved with sand compaction piles (SCP). In order to find the behavior of the clay ground improved with SCP, extensive centrifuge model experiments were carried out for each of the SCP replacement ratio of 20, 40, and $70\%$, the non-plastic fine contents in sand of 5, 10, and $15\%$, and the ratio of the improved width to the loaded area (W/B) of 1, 2, and 3. The commertially available software of FEM, CRISP, was used to analyze test results by performing numerical estimations. In these numerical analyses the sand compaction piles and the clay ground were simulated as a linear elastic and plastic constitutive model and the modified Cam-clay model, based on Critical State Soil Mechanics, respectively.

• Tunnel and Underground Space
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• v.9 no.2
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• pp.114-130
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• 1999

It is very important to study on the structural behaviors of structurally damaged tunnel linings. A series of centrifuge model tests were performed in order to investigate different behaviors of tunnel linings. A 1/100-scaled aluminum horseshoe tunnel linings with a radius 5 cm, height 8 cm were buried in a depth with dry Joomunjin standard sand, the relative density of which was 86%. Such sectional forces as bending moments and thrusts along the tunnel circumference were measured by twelve strain gages. Earth pressures in soil mass and on the outside of lining model were estimated by pressure transducers, ground surface settlements at a center and edges by using LVDTs.

• Proceedings of the Korean Geotechical Society Conference
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• 2008.03a
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• pp.553-562
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• 2008

A remediation technique for buried pipeline system subject to permanent ground deformation is proposed. Specifically, EPS (expanded polystyrene) geofoam blocks are used as low density backfill, thereby reducing soil restraint and pipeline strains. In order to evaluate this remediation technique, a series of 12 centrifuge model tests with HDPE pipe were performed. The amount or spatial extent of the low density backfill was varied, as well as the orientation of the pipe with respect to the fault offset. Specifically, in the $-63.5^{\circ}$ test, the orientation was such that the pipe was placed in flexure and axial tension. The $-85^{\circ}$ orientation placed the pipe mainly in flexure. In all cases, the behavior of the remediated pipe was compared to that for the unremediated pipe. The geofoam backfill was successful in improving pipe behavior for two of the three pipe/fault orientations. However, for the $60^{\circ}$ orientation, the pipe buckled in compression irrespective of the geofoam backfill.

• Proceedings of the Korean Geotechical Society Conference
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• 2006.03a
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• pp.394-401
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• 2006

This study developed two dimensional finite element program(FE-SCP) for the analysis of a composite ground reinforced by sand compaction piles with a low area replacement ratio based on the Mohr-Coulomb elastic perfectly plastic constitutive model. Program FE-SCP give some conveniences to users such as automatic mesh generation according to the replacement ratio and the effective sand pile diameter in the post processor. Also, it contains optimum processor in calculation of In-situ stress equilibrium considering different coefficient of earth pressure between sand pile and surrounding clay. Estimated stress-strain behavior using FE-SCP and the measured one from a centrifuge test showed good agreement comparing to the result from a general finite element program.