• 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.

• Journal of the Korean GEO-environmental Society
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• v.8 no.2
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• pp.29-39
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• 2007

In this study, the centrifugal tests were fulfilled to analyze the displacement characteristics caused by the embankment construction on soft ground. Embankment of height, undrained shear strength and with or without geotextile were selected to evaluate the displacement characteristics of soft ground by embankment. As a result, the replacement section without geotextile showed the parabola shape. The replacement section with geotextile showed the trapezoidal shape which represents the uniform settlements. The replacement angle is increasing nearly lineally with increasing the height of embankment and G-level. The position, where the maximum horizontal displacement occurred, was between $0.24H_0$ and $0.35H_0$ and was at $0.3H_0$ on the average. In the case of with and without geotextile, the relationship between the maximum settlement of ground(S) and maximum horizontal displacement(${\delta}_m$) was ${\delta}_m$ = 0.60S, ${\delta}_m$ = 0.54S, respectively.

• Journal of the Korean GEO-environmental Society
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• v.6 no.1
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• pp.73-82
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• 2005

Generally, to evaluate a slope stability of the geosynthetic reinforced soil slope, the modified version of limit equilibrium method can be used. In most cases, resisting effects of reinforcement are dealt with considering an increased shear strength on the potential slip surface. However, it is not clear that the methods satisfy all three equilibrium equations. In this study, the new slope stability analysis method in which not only reinforcing effects of geosynthetics can be considered but also all three equilibrium equation can be satisfied is proposed. A number of illustrative examples, including published load test of large-scale reinforced retaining wall and centrifuge model tests on the geotextile reinforced soil slopes, are also analyzed. As a result, it is shown that the newly suggested method produces a relatively accurate factor of safety.

• Journal of the Korean GEO-environmental Society
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• v.12 no.6
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• pp.5-15
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• 2011

In this study, centrifuge model tests were performed to investigate stress concentration ratio, stress characteristics of soft clay ground improved by granular compaction piles with changes of piles type, loading condition and area replacement ratio. From the results of rigid loading tests, while vertical stresses acting on clay ground is similar, vertical stresses acting on GCP is larger than those acting on SCP with same replacement ratio. Also, average stress concentration ratio is increased proportionally with increasing the area replacement ratio of GCP and SCP. It was evaluated that average stress concentration ratio of soft clay ground improved by GCP is larger than that of SCP. As a result of flexible loading tests, stress concentration ratio is the highest when replacement ratio of GCP and SCP is 40%. Average stress concentration ratio of soft clay ground improved by GCP is a little more higher than is improved by SCP.

• Journal of the Korean GEO-environmental Society
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• v.24 no.2
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• pp.13-24
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• 2023

Tunnels may undergo a larger or a smaller response compared with the free-field soil. In the pseudo-static procedure, the response of the tunnel is most often characterized by a curve that relates the racking ratio (R) with the flexibility ratio (F), where R represents the ratio of the tunnel response with respect to the free-field vibration and F is the relative stiffness of the tunnel and the surrounding soil. A set of analytical and empirical curves that do not account for the depth and the aspect ratio of the tunnel are typically used in practice. In this study, a series of dynamic analyses are conducted to develop a set of F-R_m relations for use in a frame analysis method. R_m is defined as an adjusted R where the rocking mode of deformation is removed and only the racking deformation is extracted. The numerical model is validated against centrifuge test recordings. The influence of aspect ratio, buried depth of tunnel on results is investigated. The results show that R_m increases with the increase of the buried depth and the aspect ratio. The widely used F-R relations are highlighted to be different compared with the obtained results in this study. Therefore, the updated F-R_m relations with proposed equations are recommended to be used in practice design. The rocking response decreases with either the decrease of the difference of stiffness between surrounding soil and tunnel or the larger aspect ratio of the tunnel section.

• Journal of the Korean Geotechnical Society
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• v.34 no.1
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• pp.25-35
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• 2018

Geocentrifuge tests are performed to investigate the structure-soil-structure interaction of shallow foundations that have various sizes. The soil specimen is prepared by using the air-pluviation, and the dynamic responses of the foundation are monitored with separation distances between the two foundations and the embedment. During the centrifugal test, the measured ground acceleration shows a tendency to increase with the increase of the input seismic amplitude, and maximum acceleration is measured at the surface due to the ground amplification. As the separation distance between the two foundations decreases, the ratio of the response spectral acceleration (RRS) increases and the period at the peak RRS decreases due to the structure-soil-structure interaction (SSSI). The RRS of the two foundations tends to decrease when the foundations are buried in the ground at the same separation distance.