• Journal of the Korean Geotechnical Society
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• v.37 no.6
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• pp.39-50
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• 2021

Recently, as the occurrence of earthquakes with a magnitude of 5.0 or higher in Korea increases, many studies and interests in seismic design are increasing. A lot of damage was caused by the Pohang earthquake in 2017, and port facilities such as a breakwater were also damaged. This study analyzed the dynamic behavior of the upright breakwater, an external facility, based on a centrifugal model experiment. A series of centrifugal model test was conducted by three different seismic waves such as Pohang Earthquake Wave, Artificial Wave I, and II. As a result, the dynamic behavior of upright breakwater was analyzed. The review showed that acceleration amplification tends to be suppressed as breakwater foundation ground increases support and stiffness through DCM reinforcement and riprap replacement.

• 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.38 no.11
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• pp.119-135
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• 2022

This paper used dynamic centrifuge tests to examine the seismic response for a deep temporary retaining wall with four input motions of 100, 1,000, and 2,400 years of return periods. The centrifuge model was designed based on an actual deep excavation design with a 50 m maximum excavation depth. The model backfill was prepared with dry silica sand at a relative density of 55%, and the retaining wall was modeled as a 24.8 m height diaphragm wall supported by struts. Acceleration response was amplified at the backfill surface, top of the wall, and near bedrock. However, in the middle of the model, input motion was de-amplified. The member forces of the wall and strut induced by the seismic load, which excited, were compared with the member force at rest condition. The wall's maximum negative and positive moments were increased to 36% and 10% compared to the maximum moment at rest. The maximum axial force increases to 70% of the at rest axial force on the bottom strut. The equivalent static analysis using Mononobe-Okabe (M-O) and Seed-Whitman (S-W) seismic earth pressures were compared to the centrifuge results. Considering the bending moment, the analysis results with the M-O theory underestimates but that with the S-W theory overestimates.

• Journal of the Korean GEO-environmental Society
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• v.7 no.6
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• pp.133-143
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• 2006

A fully coupled effective stress dynamic analysis procedure for modeling seismic liquefaction on slope is presented. An elasto-plastic formulation is used for the constitutive model UBCSAND in which the yield loci are radial lines of constant stress ratio and the flow rule is non-associated. This is incorporated into the 2D version of Fast Lagrangian Analysis of Continua (FLAC) by modifying the existing Mohr-Coulomb model. This numerical procedure is used to simulate centrifuge test data from the Rensselaer Polytechnic Institute (RPI). UBCSAND is first calibrated to cyclic direct simple shear tests performed on Nevada sand. Both pre- and post-liquefaction behaviour is captured. The centrifuge test is then modeled and the predicted accelerations, excess porewater pressures, and displacements are compared with the measurements. The results are shown to be in general agreement. The procedure is currently being used in the design of liquefaction remediation measures for a number of dam, bridge, tunnel, and pipeline projects in Western Canada.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.32 no.3C
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• pp.85-94
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• 2012

This paper described a centrifuge study in order to investigate ground-underground hollow structure interaction-induced rocking behavior in liquefied ground. Uplift of the underground hollow structures is initiated due to liquefaction in sandy grounds when the ground is exposed to a strong shaking during earthquakes because the apparent unit weight of these structures is smaller than that of the liquefied soil. In order to evaluate the dynamic behavior of the underground hollow structure and the effects of original subsoil during the uplifting, model tests were performed by changing the relative density of the original subsoil and installing an acrylic box as a trench. The results of the present study show that rocking behavior of the underground hollow structure due to shear deformation of the surrounding subsoil or lateral movement from the original subsoil contributed to large magnitude of the uplift due to strong shaking.

• Land and Housing Review
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• v.6 no.3
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• pp.147-152
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• 2015

Site coefficient and amplification factor of current domestic Seismic Design Code based on American Seismic Code, have no consideration for the domestic ground condition in which the base rock is normally placed within 30m form the surface. By previous studies, the measured spectral acceleration of the result of dynamic centrifugal test and analysis was smaller than the design spectral acceleration for the period over 1.5 sec. Accordingly, in this study structural analysis and design using dynamic centrifugal test result for pile foundation were achieved, and the quantity of concrete and reinforcement of wall frame was compared with each other. Comparison results of cost using KBC the design spectral acceleration of SC, SD site and SDS, the quantity of reinforcement using SDS for SD site was 17~23% smaller than using the design code SD site.

• Journal of the Korean GEO-environmental Society
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• v.12 no.1
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• pp.61-70
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• 2011

The impact protection system consists of an arrangement of circular sheet pile cofferdams-denoted dolphin structuredeeply embedded in the seabed, filled with crushed rock and closed at the top with a robust concrete cap. Centrifuge model tests were performed to investigation the behaviors of dolphins in this study. Total 7 quasi-model tests and 11 dynamic model tests were performed. The main experimental results can be summarized as follows. Firstly, The experimental force-displacement results for quasi-static tests show a limited influence on the initial stiffness of the structure from the change in fill density and the related change in the stiffness of the fill. And by comparing the dissipation at the same dolphin displacement it was found that the denser fill increase the dissipation by 16% for the 20m dolphin and by 23% for the 30m dolphin. The larger sensitivity for the large dolphin is explained by a larger contribution to the dissipation from strain in the fill. In low level impacts the dynamic force-response is up to 26~58% larger than the quasi-static and the dissipation response is showed larger in small displacement. Hence, it is concluded conservative to use the quasi-static response characteristics in the approximation of the response, and it is further concluded that the dolphin resistance to low level impacts is demonstrated to be equivalent and even superior to the high level impacts.

• Land and Housing Review
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• v.5 no.2
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• pp.115-120
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• 2014

Site coefficient and amplification factor of current domestic Seismic Design Code (KBC-2009) have no consideration for the domestic ground condition in which the base rock is normally placed within 30m form the surface. Accordingly, in this study dynamic centrifugal test and analysis for pile foundation into clay were achieved. and the response spectrums of free surface and basement were compared with each other. Within the period 1sec., the measured spectral acceleration of free surface and basement was bigger than the design spectral acceleration of SC and SD site. However the measured spectral acceleration of free surface and basement for the period over 1.5sec. was smaller than the design spectral acceleration of SC site. There was no severe difference of spectral acceleration according to the upper structure, embedded depth of foundation and free surface conditions. Consequently, normal domestic apartment housing for the period range over 1.5sec. could be design more economically applying these test result.

• Journal of the Korean Geotechnical Society
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• v.26 no.8
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• pp.67-75
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• 2010

In this study, a series of 1 g shaking table tests were carried out for a single pile in soft clay with various input acceleration amplitudes and frequencies. Based on the results, dynamic p-y curves were drawn and, in turn, the dynamic p-y backbone curve was formed by connecting the peak points, corresponding to the maximum soil resistance, of the dynamic p-y curves. In order to represent the p-y backbone curve numerically, Matlock's p-y formulations for clay was used to find the initial stiffness ($k_{ini}$) and the ultimate capacity ($p_u$) of the clay, both of which are required to formulate the p-y backbone curve as a hyperbolic function. The suggested p-y backbone curve was verified through comparisons with currently available p-y curves as well as other researchers' centrifuge test results and numerical analysis results.

• Journal of the Korean Geotechnical Society
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• v.35 no.2
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• pp.5-17
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• 2019

Dynamic centrifuge model test was conducted to evaluate the dynamic stability of the pile-supported slab track method during dynamic railway loading and earthquake loading. The centrifuge tests were carried out for various condition of embankment height and soft ground depth. Based on test results, we found that the bending moment was increased with embankment height and decreased with soft ground depth. In addition, it was confirmed that the pile-supported slab track system could have dynamic stability for short-period seismic loading. However, in case of long-period seismic loading, such as Hachinohe earthquake, the observed maximum bending moment reached to pile cracking moment at the return period of 2,400 year earthquake. The criterion of ratio between embankment height and soft ground depth was suggested for dynamic stability of pile-supported slab track system.