• Tunnel and Underground Space
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• v.22 no.3
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• pp.214-220
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• 2012

Deformation behaviour of rock mass around an opening measured during tunnel excavation is very important in order to assess the stability of the tunnel. Unfortunately displacement measured only after the installation of displacement measuring device can be acquired, which results in inevitably excluding the pre-displacement occurred and accumulated before the displacement measuring devices are installed. So it is very important to consider the pre-displacement based on the elapsed time before zero reading after deformation behaviour started. In this study, the accuracy of total estimated displacement depending on the distance between face and measurement position is calculated by statistical non-linear fitting on measurable displacement data. Besides, the influence of the unavoidable measurement error is considered by using Monte-Carlo simulation. As a result, the faster the initial reading started and the smaller the measurement error is, the higher the accuracy of estimating total displacement is obtained.

• Journal of the Society of Naval Architects of Korea
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• v.45 no.1
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• pp.42-53
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• 2008

The two dimensional PIV (particle image velocimetry) measurement technique is applied to water flow in a narrow cavitation tunnel. The nearly homogeneous and isotropic turbulent flows are generated by the honeycomb installed in the tunnel and visualized with a PIV technique. The velocities in the measurement plane at the tunnel centerline 184cm downward from the honeycomb were measured and calculated by an image correlation technique. The turbulent properties are evaluated and each term in the turbulent kinetic energy equation is calculated for the conditions with different internal pressures. Lowering the internal pressure gives an effect on the turbulent flow due to growing bubbles which are resolved in the water. The turbulent kinetic energy in the measurement plane is decayed much slower than those of other research results carried out with wind tunnels. With decreasing the tunnel internal pressures the turbulent intensities are increased about 1.5 times and the anisotropic tendency is also increased.

• Journal of the Society of Naval Architects of Korea
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• v.60 no.2
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• pp.135-145
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• 2023

Developing high-fidelity Computational Fluid Dynamics (CFD) simulation methods used to evaluate the airwake characteristics along a flight deck of a large ship, the various kind of data such as actual ship measurement and wind tunnel results are required to verify the accuracy of CFD simulation. Inflow velocity profile at the bow, local unsteady flow field data around the flight deck, and highly reliable wind tunnel data which were measured after reviewing Atmospheric Boundary Layer (ABL) simulation and Reynolds Number effects were also used to determine the key parameters such as turbulence model, time resolution and accuracy, grid resolution and type, inflow condition, domain size, simulation length, and so on in STAR CCM⁺. Velocity ratio and turbulent intensity difference between Full-scale CFD and actual ship measurement at the measurement points show less than 2% and 1.7% respectively. And differences in velocity ratio and turbulence intensity between wind tunnel test and small-scale CFD are both less than 2.2%. Based upon this fact, the selected parameters in CFD simulation are highly reliable for a specific wind condition.

• Tunnel and Underground Space
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• v.9 no.4
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• pp.296-305
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• 1999

In ordinary back analysis it if hardly possible to obtain the mechanical properties of tunnel lining by using commonly measured displacements of tunnel lining, because only a few displacements could be measured at the site. Therefore, it is necessary to develop a new method which can evaluate the state of stresses of tunnel by using measured data. In this study, in order to assess tunnel lining stability by estimating its stresses with a few measured displacements, a formulation of back analysis method was proposed. The accuracy of results were investigated through the parametric study for several types of measurement model of two dimensional elastic lining. This new back analysis method to assess tunnel lining stresses and strains with a few numbers of measured displacements showed high accuracy and good applicability when compared to the results of numerical experiments by FEM. The method has been tested on subway tunnel and its applicability has been confirmed by comparing field and analytical data. It is verified that the stress on the tunnel lining can be obtained by only more than 3 point of input displacements without any condition of external loads.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.4
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• pp.758-765
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• 2016

This paper is a follow-up paper to the publication, "Development of Tunnel-Environment Monitoring System and Its Installation I - Monitoring System and Measurement in Subway Tunnel" [1]. An environment monitoring system was installed in the 20.3-km-long Gumjung tunnel, which has the general structure of a high-speed double-track railway tunnel. Data were collected for approximately one year. Monthly and daily data were obtained and analyzed for the temperature and relative humidity in summer and winter months. This paper discusses the environmental characteristics at different positions in the tunnel. The results are expected to be widely used in studies on tunnel ventilation and the improvement of air quality and thermal environments.

• Proceedings of the Korean Geotechical Society Conference
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• 1999.03a
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• pp.285-292
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• 1999

Recent development cases of transportation utilities using tunnelling method in metropolitan sites have been increased due to the heavily complex environments and restrictions of construction works. The progress of tunnel design and construction to be supported by the tunnel analysis and measurement techniques using computers have increased adoptions of large section tunnels. In this paper, many factors to be considered in designing large section tunnels are discussed and the case of the construction of the subway station tunnel which is recently completed is introduced. This tunnel has a width of 24 m, a height of 16 m, and a excavation section area of 366 ㎡.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.41 no.1
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• pp.10-16
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• 2013

This paper discussed a procedure for noise certification of Aircraft and predicting the full scale over-flight noise of propeller from acoustic wind tunnel measurement of small scale propeller. Noise Certification Procedures is established from International Civil Aviation Organization(ICAO). The data manipulations are then discussed in extrapolation to simulation flight distance and flight simulation. One of the most important point of flight simulation is adjustments for differences between wind tunnel test conditions and flight test conditions. To simulated the noise level estimation procedure for noise data post-process, simulate procedures from data of the wind tunnel noise measurement and the flight noise measurement by using a 7kg degree UAV. This study confirmed an effectively noise estimation procedures by wind tunnel noise test and flight noise test.

• Journal of the Korean Society of Radiology
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• v.14 no.4
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• pp.385-390
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• 2020

In the present, external environmental factors affect human health. In particular, the most important issue is fine dust in these days. Because fine dust is inhaled through the human respiratory system is known to be harmful to health. Tunnels for cars and people can also be easily seen around us. This study, the amount of scattering radiation was measured for walkable tunnels about dust. For the measurement method, dust and radiation dose in the tunnel were measured on good weather (fine dust level: 0 ~ 30 ㎍/㎥) and normal day (fine dust level: 0 ~ 80 ㎍/㎥). The measurement resulted in an increase of 10~20 % of dust in the center of the tunnel on a good weather day and an increase of 20~30 % of dust in the center of the tunnel on normal weather. On the other hand, the results of tunnel measurement of radiation dose increased by 10~20 % at the center of the tunnel non-depending on the weather. As a result, pedestrians should pay attention to scattering dust and scattered radiation while moving through the tunnel. Therefore, it is recommended to wear a filter mask of PM2.5 or less during frequent tunnel walking.

• Proceedings of the Korean Geotechical Society Conference
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• 2008.03a
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• pp.766-777
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• 2008

Currently in increasing number of urban tunnels with small overburden are excavated according to the principle of the New Austrian Tunneling Method (NATM). Successful design, construction and maintenance of NATM tunnel demands prediction, control and monitoring of ground displacement and support stress high accuracy. A magnetic anisotropy sensor is used for nondestructive measurement of stress on surfaces of a ferromagnetic material, such as steel. The sensor is built on the principle of the magneto-strictive effect in which changes in magnetic permeability due to deformation of a ferromagnetic material is measured in a nondestructive manner, which then can be translated into the absolute values of stresses existing on the surface of the material. This technique was applied to measure stresses of H-beams, used as tunnel support structures, to confirm expected measurement accuracy with reading error of about 10 to 20 MPa, which was confirmed by monitoring strains released during cutting tests The results show that this method could be one of the promising technologies for non-destructive stress measurement for safe construction and maintenance of underground rock structures encountered in civil and mining engineering.

• The Journal of the Convergence on Culture Technology
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• v.10 no.1
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• pp.559-563
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• 2024

Currently, in Korea, large-scale, deep excavations are being carried out adjacent to structures due to overcrowding in urban areas. for adjacent excavations in urban areas, it is very important to ensure the safety of earth retaining structures and underground structures. accordingly, an automated measurement system is being introduced to manage the safety of subway tunnel structures. however, the utilization of automated measurement system results is very low. existing evaluation techniques rely only on the maximum value of measured data, which can overestimate abnormal behavior. accordingly, in this study, a vast amount of automated measurement data was analyzed using the Gaussian probability density function, a technique that can quantitatively evaluate. highly reliable results were derived by applying probabilistic statistical analysis methods to a vast amount of data. therefore, in this study, the safety evaluation of subway tunnel structures due to adjacent excavation work was performed using a technique that can process a large amount of data.