• Tunnel and Underground Space
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• v.17 no.1 s.66
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• pp.66-74
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• 2007

The analysis of ground subsidence stability was conducted for the residential area located on the limestone corrosion zone. For the investigation of the cavity distribution in limestone region, various geophysical investigations such as electroresistivity tomography, electromagnetic prospecting are carried out. Geotechnical field tests with drilling are also carried out for the evaluation of the ground characteristics. Based upon their results, numerical modeling is performed for the simulation and prediction of the ground subsidence with the conditions of cavity geometry and groundwater level. The main factor to cause the ground subsidence is estimated as the draw down of the groundwater level below soil overburden, which disturbs the mechanical equilibrium of ground and drives washing away the overburden soil through the cavity and solace subsidence. It seemed that it is essential to maintain the groundwater level continuously above the shallow cavity for the prevention of the ground subsidence on the limestone corrosion zone.

• Tunnel and Underground Space
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• v.26 no.1
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• pp.46-58
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• 2016

In this study, a LIDAR laser scanner was used to scan a rock slope around Mt. Gwanak and to produce point cloud from which directional information of rock joint surfaces shall be extracted. It was analyzed using two different algorithms, i.e. Ball Pivoting and Wrap algorithm, and four sampling intervals, i.e. raw, 2, 5, and 10 cm. The results of Fuzzy K-mean clustering were analyzed on the stereonet. As a result, the Ball Pivoting and Wrap algorithms were considered suitable for extraction of rock surface orientation. In the case of 5 cm sampling interval, both triangulation algorithms extracted the most number of the patch and patched area.

• Tunnel and Underground Space
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• v.25 no.6
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• pp.527-533
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• 2015

This study performed an on-site demonstration of the topographic surveying technique at a large-scale open-pit limestone mine in Korea using a fixed-wing unmanned aerial vehicle (UAV, Drone, SenseFly eBee). 288 sheets of aerial photos were taken by an automatic flight for 30 minutes under conditions of 300 m altitude and 12 m/s speed. Except for 37 aerial photos in which no keypoint was detected, 251 aerial photos were utilized for data processing including correction and matching, then an orthomosaic image and digital surface model with 7 cm grid spacing could be generated. A comparison of the X, Y, Z-coordinates of 4 ground control points measured by differential global positioning system and those determined by fixed-wing UAV photogrammetry revealed that the root mean squared errors were around 15 cm. Because the fixed-wing UAV has relatively longer flight time and larger coverage area than rotary-wing UAVs, it can be effectively utilized in large-scale open-pit mines as a topographic surveying tool.

• Tunnel and Underground Space
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• v.19 no.5
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• pp.407-420
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• 2009

In this study geostatistical technique using indicator kriging was performed to evaluate the optimal rock mass classification by integrating the various geophysical information such as borehole data and geophysical data. To get the optimal kriging result, it is necessary to devise the suitable technique to integrate the hard (borehole) and soft (geophysical) data effectively. Also, the model parameters of the variogram must be determined as a priori procedure. Iterative non-linear inversion method was implemented to determine the model parameters of theoretical variogram. To verify the algorithm, behaviour of object function and precision of convergence were investigated, revealing that gradient of the range is extremely small. This algorithm for the field data was applied to a mountainous area planned for a large-scale tunneling construction. As for a soft data, resistivity information from AMT survey is incorporated with RMR information from borehole data, a sort of hard data. Finally, RMR profiles were constructed and attempted to be interpreted at the tunnel elevation and the upper 1D level.

• Tunnel and Underground Space
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• v.15 no.5 s.58
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• pp.359-368
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• 2005

In case the overburden of a tunnel is too low to adopt NATM, cut and cover method generally can be chosen as alternative. However, in tunneling some area with very low or no overburden between two mountains, the cut and cover method requires additional construction of a couple of tunnel portals and the maintenance of portal slopes until backfilling is completed. As a solution for this problem, increasing the tunnel overburden by raising the ground level can be effective. This paper presents the case study for tunneling at C240 site in Taiwan High Speed Railway(THSR) in which soil-cement filling method was used for pre-banking before tunnel excavation. Cement content of filling material was $2\~4\%$ and thickness of filling a round was $130\~250\;mm$. The stability evaluation for the soil-cement slope and concrete lining of low cover tunnel was conducted by numerical analysis.

• Tunnel and Underground Space
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• v.19 no.4
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• pp.275-286
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• 2009

In order to establish the causes and measures for technical risks that occur in various ground conditions when a subsea tunnel is excavated, it is important to configure expected risk scenarios. In addition, when the risk scenarios are classified because the scenario that occurs along all tunnel route and the scenario limited to some area are considered together, a logical framework with systematic and organized responses can be provided for project managements. In this research, project risk scenarios and management elements were configurated, and the project schedule was established for the management techniques to the risk scenario. The risk scenarios expected in a subsea tunnel were classified into a common risk scenario and a special risk scenario, and the concept which can combine with the project management elements was derived.

• Tunnel and Underground Space
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• v.23 no.2
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• pp.141-149
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• 2013

The thermal analysis is carried out for a geological disposal system developed for the final disposal of a ceramic high-level waste from pyroprocessing of PWR spent fuel. The horizontal disposal tunnel type is considered with the distance of 2 m between the disposal canisters and the tunnel spacing of 25 m. The temperature distributions around the disposal canisters are calculated for the horizontal tunnel based on the conceptual design. The thermal performance analysis is carried out using a FEM program, ABAQUS. The performance analysis shows that the peak temperature in a disposal system outside the disposal canister is lower than $100^{\circ}$, which meets the thermal criterion of the disposal system. According the analysis, the peak temperature for the disposal canister located boundary of the disposal system is lower by $3^{\circ}$ than that for the canister at the central area. This implies the disposal density can be improved by locating more disposal canisters along the boundary.

• Magazine of the Korean Society of Agricultural Engineers
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• v.40 no.5
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• pp.68-79
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• 1998

In the years, the concern about high-strength concrete which is new material has been heightened as a result of active research and development. Recently, as the building structure has been being bigger, higher, longer and more specialized, the demand of material with high-strength concrete for building has been increasing. The demand of high -strength concrete is expected to increase with expansion of usage about the complex concrete structures such as bridge structure as well as nuclear plants, underground structures, hydraulic structures and arctic area sturctures. In this research, silica-fume was used as an admixture in order to get a high-strength concrete. Water/binder ration was limited no more than 18 percent and the amount of unit cement was increased. In this study, a number of trial in concrete mix was carried out to get optimal mix design, and the target slump with $10{\pm}2cm$ was set for in-situ construction. High-strength concrete with cylinder strength of 1,200kgf/$cm^2$ in the 28-days was produced and tested. The static test was carried out to measure the ultimate load, the initial load of flexural and diagonal cracking, crack patterns, fracture modes. The load versus strain and load versus deflection relations were obtained form the static test. The test results were compared with the shear strengths predicted by the equations of ACI code 318-89 and orther researchers. Based on the test results, shear strength equation of reinforced concrete beam using high strength concrete was proposed. Form an evaluation of the results of this experimental investigation, it was concluded that shear strength after diagonal tention cracking diminished with the increase in compressive strength for beams.

• Proceedings of the Korean Society of Surveying, Geodesy, Photogrammetry, and Cartography Conference
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• 2004.11a
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• pp.405-410
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• 2004

In mid-90's, the Korean government introduced the GIS(Geographic Information System) to digitalize every topography of national land and thereby, index locations and attributes of various urban facilities to construct a system whereby every information could be managed and operated in an integrated way, but the reliability of such geographic information has yet to be tested, much less its modification, complementation and maintenance. Under such circumstances, this study was aimed at constructing a reference point infrastructure for Seoul and Kyonggi area and comparing the data obtained from the GPS operation and various facility location data with the existing GIS data to address the problems of GIS operation and suggest their solutions. As a result of calculating the GPS reference point data and analyzing the deviations of the unknown point data in comparison with the fixed point ones, it was found that the horizontal location values were reliable within +/- 5cm, but that the above-sea level values varied as much as 1.4m depending on the deployment of pre-set fixed points determined by the direct level gauging. In addition, as a result of directly surveying major facilities around the roads based on the coordinates of the urban reference points networked with such a reference point system to check their conformity to existing data, it was confirmed that the difference was as wide as 2m. Such differences may be attributable to the fact that the data with their geographic information not confirmed are used as basic data for GIS. Hence, this study suggests the ways to set the absolute geographic data based on reference points and test the reliability of existing data and thereby, suggests a methods to solve the problems.

• Economic and Environmental Geology
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• v.34 no.6
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• pp.595-600
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• 2001

Recently, interests in subsidence hazard have been increased due to the underground construction such as subway construction and managements of abandoned mines. GIS analysis of subsidence hazard has a lot of advantages in handling of spatial data and managing database. For better result of GIS analysis, there are some necessities of modifying previous subsidence theory and model. To take surface profile into account allows the application of complicated topology. Furthermore. for 3-dimensional analysis. two subsidence profile curves that are perpendicular to each other should be considered simultaneously. Through these modifications, the model for subsidence analysis using GIS can be established. With ideal case of cavities and other conditions, GIS analysis was accomplished and meaningful results were produced. More realistic properties of cavity. soil layers, groundwater condition and topology will enable GIS analysis method to produce more reliable result and to widen the area of applications.