• Journal of the Earthquake Engineering Society of Korea
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• v.26 no.3
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• pp.117-125
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• 2022

In this study, centrifuge model tests were performed to evaluate the seismic response of multi-DOF structures with shallow foundations. Also, elastic time history analysis on the fixed-base model was performed and compared with the experimental results. As a result of the centrifuge model test, earthquake amplification at the fundamental vibration frequency of the soil (= 2.44 Hz) affected the third vibration mode frequency (= 2.50 Hz) of the long-period structure and the first vibration mode (= 2.27 Hz) of the short-period structure. The shallow foundation lengthened the periods of the structures by 14-20% compared to the fixed base condition. The response spectrum of acceleration measured at the shallow foundation was smaller than that of free-field motion due to the foundation damping effect. The ultimate moment capacity of the soil-foundation system limited the dynamic responses of the multi-DOF structures. Therefore, the considerations on period lengthening, foundation damping, and ultimate moment capacity of the soil-foundation system might improve the seismic design of the multi-DOF building structures.

• Journal of the Korean Geotechnical Society
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• v.19 no.3
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• pp.33-38
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• 2003

Marine sediment capping is a technique where clean sand is placed over contaminated sediment to reduce the migration of contaminants to the environment. The design of in-situ caps placed over marine sediment must take into consideration the self-weight consolidation of the cap and the consolidation of the sediment as a result of adding the cap layer. Centrifuge tests were adopted to simulate the effects of consolidation settlement of capped marine sediment caused by the placement of a clean sand layer. The modeling of models technique was utilized to verify the correct modeling procedures used in this study. Two centrifuge tests were conducted with the same boundary conditions at different gravitational accelerations of 100 g and 50 g. There was good agreement between these tests. It can be concluded that the centrifuge experiment is able to model consolidation settlement of capped marine sediment.

• Proceedings of the Korean Geotechical Society Conference
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• 2010.09a
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• pp.979-990
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• 2010

Although a centrifuge model test is performed with scaled models, it has a lot of advantages compared with usual scale model tests, for the reproduction of stress levels equal to a full scale test is possible. At the beginning of the Daewoo Institute of Construction Technology, a servo-motor-driven single axis actuator was introduced and has been in use with a geo-centrifuge. However, for variety of experiments and construction stage simulation, various apparatuses have been developed, such as a vacuum generator, a lateral actuator for tidal power simulation, a gravel hopper and a sand drainer for filled-up ground, and a water level controller. The apparatuses have been manufactured with enough strength and durability to be operated under specific g levels. This paper presents the properties of the apparatuses and the results of the tests performed with those.

• Proceedings of the Korean Geotechical Society Conference
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• 2002.03a
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• pp.381-388
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• 2002

A series of centrifuge model tests were performed to investigate the behavior of piled bridge abutment subjected to lateral soil movements induced by the construction of approach embankment. In these tests, both the depth of soft clay and the rate of embankment construction are chosen as key parameters to examine the effects on lateral soil movements. The depth of soft clay layer varies from 5.2 m to 11.6 m, and the rate of embankment construction has two types of staged construction(1m/30days, 1m/15days) and instant construction. It is shown that, the distribution of lateral flow induced by stage embankment construction has a trapezoidal distribution. And practical guidelines to check the possibility of some lateral movement of piled abutment were investigated. The validity of the proposed guidelines by centrifuge test was compared with the observed performance by lateral movement index, F(Japan Highway Public Corporation) and modified I index(Korea Highway Corporation). Based on the results obtained, the critical values of F and modified I, as a practical guidelines, are proposed to 0.03 and 2.0, respectively.

• Journal of the Korean Geotechnical Society
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• v.20 no.8
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• pp.41-48
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• 2004

Several centrifuge modelling tests were performed to compare sand compaction pile (SCP) with gravel compaction pile (GCP) at the point of bearing capacity. SCP and GCP were installed as 30, 40, 50, 60, 70% of replacement ratio in cylindrical model tank (diameter = 20 cm, height = 40 cm), and the loading tests were carried out to analyze the bearing characteristics of soft clay ground reinforced by SCP and GCP. As a result of loading tests, the bearing capacities of soft grounds reinforced by SCP and GCP increase with increasing replacement ratio of pile, and a GCP reinforced ground has larger bearing capacity than that of a SCP reinforced ground. Several proposed bearing capacity equations for ground reinforced by SCP or GCP were compared with loading test results.

• Proceedings of the Korean Geotechical Society Conference
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• 2009.03a
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• pp.278-287
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• 2009

This thesis studied effect of zoning on seepage flow in concrete faced gravel-fill dam (CFGD) designed to have selected main rockfill or gravel-fill zone, Zone 3Bs with higher permeability to enhance the safety against accidental water infiltration into the dam. For this purpose, centrifuge model tests with two cases, with and without Zone 3Bs, were performed in order to investigate the necessity and the function of Zone 3Bs. Model dams were made by soil samples with modified coefficients of permeability and concrete faced slab was simulated with aluminum alloy. Water infiltration was simulated by rising water table over cracks on the facing. Behaviors of model dams were measured by LVDTs, strain gages, pore water pressures and cameras. Form the results of centrifuge tests, it was found out that the Zone 3Bs acts as a protection of main gravel-fill zone by inducing flow paths for infiltrated water into it as well as by draining off the infiltrated water out of the dam in a short time.

• Journal of the Korean Geotechnical Society
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• v.28 no.2
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• pp.23-31
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• 2012

The purpose of this study is to analyze earth pressure acting on a circular shaft-tunnel considering arching effect by centrifuge modeling test on sands. The centrifuge testing method provides a way to model an in-situ stress state condition with a stress gradient within a laboratory specimen. A small-scale model of circular shaft-tunnel, which has a real diameter of 6.0 m and height of 15.0 m, was designed and tested twice under 75g-level. Additionally, an effect of excavation was presented by separating two segments of circular shaft wall to find behavioral properties and strength of earth pressure along with excavating ground. The test results were compared with those of the proposed earth pressure equation. The test results showed that earth pressure decreased by about 70% in comparison with existing two-dimensional earth pressure. This fact might be attributed to three-dimensional arching effects.

• Journal of Ocean Engineering and Technology
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• v.20 no.5 s.72
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• pp.49-56
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• 2006

In this thesis, centrifuge model experiments and numerical analyses were carried out to investigate the behavior of an excavated slope in soft clay ground. Centrifuge model tests were performed with various slopes for the excavated ground, such as 1:1.5 and 1:2. Pore pressuresthe model ground were measured to find their effects on the stability of the excavated slope. These experiments showed that the model with 1:2.5 maintained its stability within a short period of time and failed gradually. Therefore, anexcavated slope of soft soil with this slope might maintain stable conditions within a certain time. The mode1 with a 1:3 slope was observed to maintain a very stable condition, showing insignificant deformation in the ground after being excavated. Numerical analyses with PLAXIS, a commerciallyavailable software implemented with the finite element numerical technique, were performed to find the pore pressure distribution within the ground mass and the deformation of the soil. From the results of numerical analysis, a negative pore pressure was developed after the excavation and thus the stability of the slope was maintained. The safety factor for slope failure was found to decrease with time because of the dissipation of negative pore pressure with time.

• Journal of the Geological Society of Korea
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• v.54 no.6
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• pp.605-614
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• 2018

For physical experiments like analogue modeling that designed for studying geological deformation, reproducibility of the deformation is important to guarantee the reliability of the experiment. In this study, the normal fault generated by extensional stress is benchmarked using a sand box model. The scaling factors for the modeling test are considered and the experiments are conducted by setting the appropriate material, extensional stress, and boundary condition in the same way as in a benchmark experiment. In addition, a large centrifuge facility is used to vary the centrifugal acceleration and extension rate in the same sized model to account for the scaling factors of the physical quantity during extensional behavior. At 1 g benchmark condition and a centrifugal field at 10 g, a constant rate of the extensional stress is implemented and the topographic evolution is reliably measured. In this study, the reliability and applicability of large centrifuge model tests are evaluated for formulating experiments designed to study geological deformation.

• Journal of the Korean GEO-environmental Society
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• v.13 no.9
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• pp.91-99
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• 2012

This study describes the investigation based on centrifuge model tests for the clay ground improved by sand compaction pile. In order to clarify the failure behavior of composite ground improved by partly and fully penetrated SCPs. And, in order to compare the effect of the penetration ratio and the replacement area ratio, nine of the centrifuge tests were carried out. From the test results, settlement reduce ratio in the fully penetrated SCPs ground is bigger than that in the partly penetrated SCPs ground. It is also evaluated that angle of the failure of composite ground improved by SCP are 26, 25, $34^{\circ}$ for As=10%, 22, $29^{\circ}$ for As=30%. And as a result of rigid loading tests, surface displacement decreases linearly with the partly penetration ratio increased.