• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.8 no.4
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• pp.279-291
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• 2010

To characterize geological features in study area for high-level radioactive waste disposal research, KAERI (Korea Atomic Energy Research Institute) has been performing the several geological investigations such as geophysical surveys and borehole drilling since 1997. Especially, the KURT (KAERI Underground Research Tunnel) constructed to understand the deep geological environments in 2006. Recently, the deep borehole of 500 m depths was drilled to confirm and validate the geological model at the left research module of the KURT. The objective of this research was to identify the geological structures around KURT using the data obtained from the deep borehole investigation. To achieve the purpose, several geological investigations such as geophysical and borehole fracture surveys were carried out simultaneously. As a result, 7 fracture zones were identified in deep borehole located in the KURT. As one of important parts of site characterization on KURT area, the results will be used to revise the geological model of the study area.

• Journal of Korean Tunnelling and Underground Space Association
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• v.15 no.2
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• pp.135-148
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• 2013

Recently, road tunnels have become longer and the plans for long and deep road tunnel have been underway in urban areas. These long and deep tunnel excavations include NATM and TBM. Shield TBM is applied to around 80% of traffic tunnels in Europe, and approximately 30% of them in other developed countries. However, as much of equipment is imported from foreign countries at high prices and distribution rate of TBM tunnel is considerably low in Korea, NATM excavation method is commonly used. To increase TBM tunnel, it is necessary to do assure economic feasibility with the supply-demand of TBM equipment. For this, the selection of standardized TBM diameter is urgently needed. Therefore, the study aims to estimate the standardized optimum section properties of TBM by examining TBM excavation cross section utilization depending on the volume of traffic, the number of lane and its cross-section type(single or double deck), and ventilation system.

• Tunnel and Underground Space
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• v.5 no.3
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• pp.223-229
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• 1995

During excavation works for underground facilities, temporary tieback wall with earth anchor system was investigated for safety's sake. An excavation 9.7 meter deep was monitored by slope inclinometer in twelve measuring points. Instrumented lateral displacements of the wall during 177 days are represented. Especially, lateral displacements of the two positions under completely different condition are compared to investigate the effect of backfilling between soldier pile and the soil behind wall. The deformation behaviors of the wall according to both depth and elasped time are discussed. Finally, a numerical analysis by the program FLAC was performed, and calculated displacements are compared to measured ones.

• Proceedings of the Korean Radioactive Waste Society Conference
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• 2010.05a
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• pp.183-184
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• 2010

From the analyses of borehole logging and hydraulic test results, the statistical properties of background fractures were characterized, and the HRDs were defined.

• Journal of Korean Tunnelling and Underground Space Association
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• v.23 no.6
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• pp.549-558
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• 2021

In order to keep infrastructures such as tunnels and underground facilities safe, cracks of concrete lining in tunnel should be detected by regular inspections. Since regular inspections are accomplished through manual efforts using maintenance lift vehicles, it brings about traffic jam, exposes works to dangerous circumstances, and deteriorates consistency of crack inspection data. This study aims to provide methodology to automatically extract cracks from tunnel concrete lining images generated by the existing tunnel image acquisition system. Specifically, we train a deep learning based semantic segmentation model with open dataset, and evaluate its performance with the dataset from the existing tunnel image acquisition system. In particular, we compare the model performance in case of using all of a public dataset, subset of the public dataset which are related to tunnel surfaces, and the tunnel-related subset with negative examples. As a result, the model trained using the tunnel-related subset with negative examples reached the best performance. In the future, we expect that this research can be used for planning efficient model training strategy for crack detection.

• Journal of Korean Tunnelling and Underground Space Association
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• v.12 no.4
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• pp.321-328
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• 2010

The study performed an actual fire experiment in order to propose the heat release rate of automobile that is the most basic architectural element for the fire safety design in a tunnel, whose importance has been recognized as the underground traffic tunnels are planned in Korean metropolitan cities. The heat release rate of a van is measured by the large scale calorimeter, in which the law of oxygen consumption is applied, and the fire expansion characteristics in a tunnel by placing two passenger cars nearby one another in the tunnel. As the results, the heat release rate of the van was revealed to be 5.9 MW, and carbon monoxide was emitted 482 ppm at a maximum. In case of two passenger car experiment for the fire expansion characteristics, the adjacent car was ignited about 3 minutes 30 seconds after the fire occurrence, and the complete fire was developed after 15 minutes. The maximum heat release was 9 MW. The results from the actual fire experiment can be an important input data for future quantitative analysis as well as an element applicable to a tunnel disaster preventive equipment design.

• Journal of Korean Tunnelling and Underground Space Association
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• v.18 no.6
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• pp.557-568
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• 2016

Squeezing is a phenomenon that may occur in deep tunneling and could bring about a large plastic deformation, tunnel closure and collapse of tunnel supports. Therefore, quantitative estimations of deformation and stress from squeezing and its possibility are necessary for establishment of a rational tunneling method. This study carried out three dimensional numerical analyses using a strain softening model in order to simulate the behaviour of squeezing and to estimate deformation and yield area around tunnels quantitatively. Numerical analyses were performed for 42 cases of various stress and strength conditions. As a result, the maximum tangential stress and strength of rock mass ratio could estimate plastic deformation and yield depth around tunnels and equations of relations between them were proposed.

• Journal of Korean Tunnelling and Underground Space Association
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• v.17 no.5
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• pp.563-573
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• 2015

For hard rock subsea tunnels the most challenging rock mass conditions are in most cases represented by major faults/weakness zones. Poor stability weakness zones with large water inflow can be particularly problematic. At the pre-construction investigation stage, geological and engineering geological mapping, refraction seismic investigation and core drilling are the most important methods for identifying potentially adverse rock mass conditions. During excavation, continuous engineering geological mapping and probe drilling ahead of the face are carried out, and for the most recent Norwegian subsea tunnel projects, MWD (Measurement While Drilling) has also been used. During excavation, grouting ahead of the tunnel face is carried out whenever required according to the results from probe drilling. Sealing of water inflow by pre-grouting is particularly important before tunnelling into a section of poor rock mass quality. When excavating through weakness zones, a special methodology is normally applied, including spiling bolts, short blast round lengths and installation of reinforced sprayed concrete arches close to the face. The basic aspects of investigation, support and tunnelling for major weakness zones are discussed in this paper and illustrated by cases representing two very challenging projects which were recently completed (Atlantic Ocean tunnel and T-connection), one which is under construction (Ryfast) and one which is planned to be built in the near future (Rogfast).

• Tunnel and Underground Space
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• v.8 no.1
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• pp.17-25
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• 1998

This paper investigates coupled thermal, mechanical and hydraulic phenomena in deep rock mass especially for underground heat storage system. Firstly, concepts of underground heat storage were presented and coupling phenomena in this area were illustrated. In order to understand the basic mechanism of thermal, hydraulic and deformation behavior in rock cavern disturbed by thermal gradient about 10$0^{\circ}C$, various numerical experiments were conducted using several codes. The study involves the behavior of fractured rock mass including rock joint. In spite of the limitation of codes modelling fully coupled effects, these codes could be applied in analysis of underground heat storage. The heat loss in rock mass, which is a major factor in heat storage, is insignificant in all results.

• Proceedings of the Korean Society for Rock Mechanics Conference
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• 2008.10a
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• pp.3-16
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• 2008

The underground construction and mining are facing many geomechanics challenges stemming from, geological complexities and stress-driven rock mass degradation processes. Brittle failing rock at depth poses unique problems as stress-driven failure processes often dominate the tunnel behaviour. Such failure processes can lead to shallow unravelling or strainbursting modes of instability that cause difficult conditions for tunnel contractors. This keynote address focuses on the challenge of anticipating the actual behaviour of brittle rocks in laboratory testing, for empirical rock mass strength estimation, and by back-analysis of field observations. This paper summarizes lessons learned during the construction of deep Alpine tunnels and highlights implications that are of practical importance with respect to constructability. It builds on a recent presentation made at the $1^{st}$ Southern Hemisphere International Rock Mechanics Symposium held in Perth, Australia, in September this year, and includes results from recent developments.