• International Journal of Highway Engineering
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• v.18 no.5
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• pp.57-62
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• 2016

PURPOSES : The objective of this study is to evaluate the effect of size and depth of cavities on the pavement failure using the full-scale accelerated pavement testing. METHODS : A full-scale testbed was constructed by installing the artificial cavities at a depth of 0.3 m and 0.7 m from the pavement surface for accelerated pavement testing. The cavities were made of ice with a dimension of 0.5 m*0.5m*0.3m, and the thickness of asphalt and base layer were 0.2 m and 0.3 m, respectively. The ground penetrating radar and endoscope testing were conducted to determine the shape and location of cavities. The falling weight deflectometer testing was also performed on the cavity and intact sections to estimate the difference of structural capacity between the two sections. A wheel loading of 80 kN was applied on the pavement section with a speed of 10 km/h in accelerated pavement testing. The permanent deformation was measured periodically at a given number of repetitions. The correlation between the depth and size of cavities and pavement failure was investigated using the accelerated pavement testing results. RESULTS : It is found from FWD testing that the center deflection of cavity section is 10% greater than that of the intact section, indicating the 25% reduction of modulus in subbase layer due to the occurrence of the cavity. The measured permanent deformation of the intact section is approximately 10 mm at 90,000 load repetitions. However, for a cavity section of 0.7 m depth, a permanent deformation of 30 mm was measured at 90,000 load repetitions, which is three times greater than that of the intact section. At cavity section of 0.3 m, the permanent deformation reached up to approximately 90 mm and an elliptical hole occurred at pavement surface after testing. CONCLUSIONS : This study is aimed at determining the pavement failure mechanism due to the occurrence of cavities under the pavement using accelerated pavement testing. In the future, the accelerated pavement testing will be conducted at a pavement section with different depths and sizes of cavities. Test results will be utilized to establish the criteria of risk in road collapse based on the various conditions.

• Journal of Korean Tunnelling and Underground Space Association
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• v.22 no.4
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• pp.337-346
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• 2020

Traffic jam and congestion in urban areas has caused the need to improve the utility of underground space. In response, research on underground structures is increasingly being conducted. Notably, a double-deck tunnel is one of the most widely used of all those underground structures. This double-deck tunnel is separated by the middle slab into the upper and lower roadways. Both vehicle load and earthquake load cause the middle slab to exhibit dynamic behavior. Earthquake-related response characteristics, in particular, are highly complex and difficult to interpret in a theoretical context, and thus experimental research is required. The aim of the present study is to assess the stability of a double-deck tunnel's middle slab of the Collapse Prevention Level and Seismic Category 1 with regard to the presence of vibration-damping Rubber Bearings. In vibration table tests, the ratio of similitude was set to 1/4. Linings and vibrating platforms were fixed during scaled model tests to represent the integrated behavior of the ground and the applied models. In doing so, it was possible to minimize relative behavior. The standard TBM cross-section for the virtual double-deck tunnel was selected as a test subject. The level of ground motion exerted on the bedrock was set to 0.154 g (artificial seismic wave, Collapse Prevention Level and Seismic Category 1). A seismic wave with the maximum acceleration of 0.154 g was applied to the vibration table input (bedrock) to analyze resultant amplification in the models. As a result, the seismic stability of the middle slab was evaluated and analyzed with respect to the presence of vibration-damping rubber bearings. It was confirmed that the presence of vibration-damping rubber bearings improved its earthquake acceleration damping performance by up to 40%.

• Journal of the Korea institute for structural maintenance and inspection
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• v.19 no.1
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• pp.120-127
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• 2015

The purpose of this study is to improve the fire prevention performance using the fire venetian blind louver subjected to burning by fire flame. The investigation is based on testing 2 full scale specimens, which is $3m{\times}3m$ module, $850mm{\times}1,500mm$ open, and $900mm{\times}900mm{\times}175mm$ venetian blind louver. Two louver thickness (1.5 and 2.0mm) were adopted. The specimens were exposed to fire flame temperature levels of ISO834 at the lower surface of the fire venetian blind louver specimens with exposure duration of one hour in Korea Institute of Construction Technology (KICT). It was found from the test results that the values of distributed temperature, decreased for all specimens for protecting to fire flame by venetian blind louver. The results of tests were a good fire prevention performance between in initial to 6 mins. At 60 minutes around ISO 834 fire loading, the percentages of distributed temperature in 500mm and 800mm height ranged between 11 and 10% respectively, regardless of louver thickness. This study, therefore, will improve the fire venetian blind louver for fire protection and prevention performance.

• Journal of the Korean Wood Science and Technology
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• v.42 no.6
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• pp.714-722
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• 2014

In the previous study, a variety of wood-based panels was thermally decomposed to manufacture carbonized boards that had been proved to be high abilities of insect and fungi repellence, corrosion and fire resistant, electronic shielding, and formaldehyde adsorption as well as sound absorption performance. Based on the previous study, carbonized medium density fiberboard (c-MDF) was chosen to improve sound absorption performance by holing and sanding process. Three different types of holes (cross shape, square shape, and line) with three different sanding thickness (1, 2, and 3 mm) were applied on c-MDF and then determined sound absorption coefficient (SAC). The control c-MDF without holes had 14% of SAC, however, those c-MDFs with holes had 16.01% (square shape), 15.68% (cross shape), and 14.25% (line) of SAC. Therefore, making holes on the c-MDF did not significantly affect on the SAC. As the degree of sanding increased, the SAC of c-MDF increased approximately 65% on sanding treated c-MDFs (21.5, 21.83, and 19.37%, respectively) compared to the control c-MDF (13%). Based on these results, composite sound absorbing panel was developed with c-MDF and MDF (11 mm). The noise reduction coefficient of composite sound absorbing panel was 0.45 which was high enough to certify as sound absorbing material.

• Journal of Korean Tunnelling and Underground Space Association
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• v.25 no.3
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• pp.201-220
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• 2023

Power cable tunnels is one of the underground structures meant for electricity transmission and are constructed using shield TBM method when transitting across urban and subsea regions. With the increasing shaft depth for tunnels excavation when the shield TBM excavated the rock mass, the review of selecting closed-type shield TBM in rocks becomes necessary. A simplified shield TBM design method is also necessary based on conventional geotechnical survey results. In this respect, design method and related design program are developed based on combined results of full-scale tests, considerable amount of accumulated TBM data, and numerical simulation results. In order to validate the program results, excavation data of a completed power cable tunnel project are utilized. Thrust force, torque, and power of shield TBM specification are validated using Kernel density concept which estimates the population data. The robustness of design expertise is established through this research which will help in stable provision of electricity supply.

• Journal of Korean Tunnelling and Underground Space Association
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• v.26 no.3
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• pp.281-301
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• 2024

The power cable tunnels which are part of the underground transmission line project, are constructed using the shield TBM method. The disc cutter among the shield TBM components plays an important role in breaking rock mass. Efficient tunnel construction is possible only when appropriate replacement occurs as the wear limit is reached or damage such as uneven wear occurs. A study was conducted to determine the wear conditions of disc cutter using a deep learning algorithm based on real-time measurement data of wear and rotation speed. Based on the results of full-scaled tunnelling tests, it was confirmed that measurement data was obtained differently depending on the wear conditions of disc cutter. Using real-time measurement data, an algorithm was developed to determine disc cutter wear characteristics based on a convolutional neural network model. Distributional patterns of data can be learned through CNN filters, and the performance of the model that can classify uniform wear and uneven wear through these pattern features.