• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.37 no.7
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• pp.661-668
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• 2009

The slosh natural frequencies, damping ratio, slosh mass and slosh force applying point of the liquid in cylindrical tank are estimated using the nonlinear least squares method in time domain. The estimated slosh model parameters are in good agreement with the results of the theoretical calculations for various liquid depths. Furthermore, this methodology will be applied to predict the sloshing parameters for a liquid propellant tank using ground experimental test-bed.

• Proceedings of the Korean Society of Agricultural Engineers Conference
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• 2003.10a
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• pp.159-162
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• 2003

In this study, it was proposed that a modified equation for estimating consolidation settlement on soft clay ground, which separate total settlement into primary and secondary settlement equation. The settlement by the proposed equation and by the measured settlements from laboratory model test was compared and verified for its application. It was appeared that the proposed equation from the laboratory model test approached to be more realistic comparing to the result of Terzaghi's equation. From the above application, it was concluded that the final settlement prediction by the Hyperbolic, Asaoka methods is needed to measure the initial period of settlement but the proposed equation could be much applicable in the lacking condition of measured data of the initial period.

• Geotechnical Engineering
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• v.7 no.1
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• pp.53-68
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• 1991

This paper aims at the investigation of various seepage behavior when rainfall infiltarates into unsaturated ground and understanding of the mechanism for slope instability due to rainfall. For this purpose an experimental study is carried out for model slopes using the test equipment which can simulate various rainfall intensity. In addition, a numerical study is performed for the same dimension and boundary condition as the experimental model. From both the experimental test and numerical analysis the progress of wetting front with time, critical amounts of rainfall, and pore-water pressure development with time are know in detail and their effects on slope stability are described.

• Tunnel and Underground Space
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• v.15 no.6 s.59
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• pp.400-410
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• 2005

During excavation of shallow tunnels in soft ground, failure mechanism around the tunnel face have major influence on the stability of tunnels. In this paper, a series of laboratory tests under plane strain condition on the small scale of a shallow tunnel considering unsupported tunnel length has been performed. The results have shown that tunnel failure mechanism changes from failure mode 1 to failure mode 2 as unsupported tunnel length increases. By comparing the experimental and the numerical results, the loosening pressure for the shallow tunnel and progressive failure have been investigated.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2004.03a
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• pp.205-210
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• 2004

The pulse detonation engine (PDE) has recently expected as a new aerospace propulsion system. The PDE system has high thermal efficiency because of its constant-volume combustion and its simple tube structure. We measured thrust of single-tube pulse detonation rocket (PDR) by two methods using the PDR-Engineering Model (full scale model) for ground testing. The first involved measuring the displacement of the PDR-EM by laser displacement meter, and the second involved measuring the time-averaged thrust by combining a load cell and a spring-damper system. From these two measurements, we obtained 130.1 N of time-averaged thrust, which corresponds to 321.2 sec of effective specific impulse (ISP). As well, we measured the heat flux in the wall of PDE tubes. The heat flux was approximately 400 ㎾/$m^2$. We constructed the PDR-Flight Mode] (PDR-FM). In the vertical flight test in a laboratory, the PDR-FM was flying and keeping its altitude almost constant during 0.3 sec.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 1999.10a
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• pp.388-395
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• 1999

There occurred a moderate size earthquake of M=5 at Whagae-Myun Hadong-Gun Kyongsangnam-Do of Korea, It caused severe damage to the buildings and other structures is Sang-Gye-Sa a famous and beautiful Buddhist Temple, The 5-story stone pagoda was standing in front of Keumdang. The top component tipped over and fell to the ground during the earthquake. In order to have accurate and quantitative estimate of the intensity of earthquake a full-scale replica is made through rigorous verification process, The completed model was mounted on the shaking table and subjected to th seismic tests. It was observed that the top component overturned at 0.16 G of EPGA when the NS component of the 1940 el Centro earthquake records was used as the input motion. A brief history of this project is presented and important test results are report6ed and their implication is discussed.

• Journal of the Korean Geosynthetics Society
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• v.16 no.4
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• pp.177-190
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• 2017

This paper presents the results of an experimental study on the effect of large underground station construction method under an existing pile supported bridge using reduced-scale model tests. A series of tests were conducted on design alternatives using 1g models for different design options for which tunnel structures were created considering the similitude law. Deformation fields obtained using the PIV analysis and LVDTs together with strains in tunnel structures were used to investigate the effect of the construction methods on the pile supported bridge. The results of the tests demonstrated that the pipe roof structure is more efficient in limiting the ground deformation as well as the settlement of bridge foundation than a 2-Arch tunnel. It is also shown that the PIV analysis can be effectively used in analyzing ground tunneling induced ground movement for cases in which a construction sequence governs ground movement.

• Journal of the Korean Geotechnical Society
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• v.27 no.3
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• pp.55-61
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• 2011

Generally, the Box-Culvert in levee is destroyed by various reasons. Especially when Box-Culvert is installed over the pile foundation in soft ground, the failure occurrs for 1) the weakness of compaction in Box-Culvert side by the differential settlement between outer ground and inner soil prism, 2) hydraulic fracturing and disturbance of Box-Culvert side soil by the repeated acting of seepage pressure at flood time. Also the side of Box-Culvert is difficult to compact and the shear resistance is reduced by more than 1/3 for the reduction of friction caused by the difference of material property. In this study, a series of model tests are conducted for the analysis of the development mechanism of outer ground and inner soil prism by the differential settlement using the pile foundation in soft ground, and cavity suppressed technique is suggested by the analysis of base plate enlargement effect.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.25 no.6
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• pp.68-74
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• 2011

The touch or step voltages which exist in the vicinity of a grounding electrode are closely related to the earth structure and resistivity and the ground current. The grounding design approach is required to determine the grounding electrode location where the hazardous voltages are minimized. In this paper, in order to propose a method of mitigating the electric shock hazards caused by the ground surface potential rise in the vicinity of a counterpoise, the hazards relevant to touch voltage were evaluated as a function of the soil resistivity ratio $\rho_2/\rho_1$ for several practical values of two-layer earth structures. The touch voltage and current on the ground surface just above the test electrode are calculated with CDEGS program. As a consequence, it was found that burying a grounding electrode in the soil with low resistivity is effective to reduce the electric shock hazards. In the case that the bottom layer soil where a counterpoise is buried has lower resistivity than the upper layer soil, when the upper layer soil resistivity is increased, the surface potential is slightly raised, but the current through the human body is reduced with increasing the upper layer soil resistivity because of the greater contact resistance between the earth surface and the feet. The electric shock hazard in the vicinity of grounding electrodes is closely related to soil structure and resistivity and are reduced with increasing the ration of the upper layer resistivity to the bottom layer resistivity in two-layer soil.

• Journal of Korean Tunnelling and Underground Space Association
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• v.14 no.3
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• pp.231-246
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• 2012

Recently, the construction of tunnel frequently involves neighboring weak ground conditions. In this case, the stabilized ground could be relaxed by the excavation of tunnel. This will create issues in terms of stability of tunnel. Major factors determining the stability of tunnel can be the direction (angle) of weak zone, the distance between tunnel and boundary of weak zone and so on. In this study, by quantifying the displacement and crack propagation during the excavation of tunnel constructed neighboring weak zone, the influence of the direction of weak zone and the distance between tunnel and boundary of weak zone on the mechanical behavior of tunnel is investigated. A series of experimental scaled model tests by changing the direction of weak zone and the distance between tunnel and boundary of weak zone, are performed and analyzed under the condition of homogeneous material. The results show that as the angle between ground surface and boundary of weak zone moves from horizontal to perpendicular plane, displacement near tunnel increases. An increased distance between tunnel and boundary of weak zone induces displacements near tunnel to decrease and stabilizes beyond a certain level of distance. These findings verify and extend the earlier studies quantitatively. Finally, an appropriate distance between tunnel and boundary of weak zone according to the angle of weak zone is justified. This fundamental insight provides the basis for a more rational design of tunnel neighboring weak ground conditions.