• Tunnel and Underground Space
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• v.16 no.3 s.62
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• pp.195-202
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• 2006

Hydro-environmental impact assessments (HEIA) in tunnel constructions have been performed through various methods including preliminary investigations, field tests, numerical simulations, and monitoring. Specially, it is very important to evaluate quantitatively groundwater inflows into tunnels as well as drawdowns caused by tunnelling. Obvious definitions between porous and fractured rock media in hvdrogeologic properties of study regions must be needed to execute HEIA for rational tunnel construction in fractured bedrocks. In this paper, we propose a HEIA on tunnel constructions in fractured rocks media resulted from various hydrogeologic field tests and numerical models on given regions and determination of systematic order, i.e. the technical road map (TRM) of HEIA. These systematic HEIAs are expected to be usefully applied to base data in tunnel construction in fractured rock media.

• Tunnel and Underground Space
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• v.29 no.1
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• pp.64-74
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• 2019

Behavior of a rock block consisting of rock joints during excavation of an underground opening is an important factor for the mechanical stability of the opening. In this study, the behavior of a rock block under different geostatic stress and joint property conditions was analyzed quantitatively. The behavior of the rock block analyzed by 3DEC numerical analysis was compared with that of the theoretical calculation, and the error between the theoretical value and the numerical analysis result was analyzed under various geostatic stress and joint property conditions. The result of the stability analysis of a rock block showed less than 5% of error with numerical simulation result, which verified the applicability of the purposed analytic solution.

• Journal of Korean Tunnelling and Underground Space Association
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• v.23 no.3
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• pp.199-209
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• 2021

Alternative methods of rock cutting have been introduced to substitute and to improve the traditional mechanical rock excavation methods (e.g., TBM and roadheader). Undercutting methods have been recently studied in some countries. In undercutting, several additional cutting parameters are involved in its cutting process compared to the traditional rock-cutting. As a fundamental study, this paper introduces the concept of undercutting method with actuated disc, lab-scaled testing system, and testing procedures of undercutting by the system. Also, we present the calculation methods of cutter forces and specific energy, and discuss the results of undercutting tests compared to those of traditional rock-cutting methods.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.43 no.4
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• pp.459-468
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• 2023

Power plant is a kind of basic industrial facility and might cause fatal industrial and human damage. In this study, the characteristics and effect of blast-induced vibration for tunnelling which underpass ○○ power plant in operation were evaluated. Previous blasting cases adjacent to industrial facilities were intensively reviewed, then allowable vibration criteria were suggested. 3 dimensional dynamic numerical analysis based on finite element method was performed to investigate particle velocity and resonance was examined by calculating the predominant frequencies. As a result, particle velocity at pump foundation which is nearest to the source was approached to the allowable criteria, therefore, the modified blasting pattern was newly suggested and confirmed the attenuation effect based on the test blasting. Consequently, appropriated decision-support procedure was established in case of adjacent blasting to industrial facilities.

• Journal of the Korean Geotechnical Society
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• v.40 no.3
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• pp.101-108
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• 2024

A system with the ability to recognize potential key blocks during tunnel construction by analyzing the rock face was developed in this study. This system predicts the formation of key blocks in advance and evaluates their safety factors. A laser scanner was used to collect a three-dimensional point cloud of the rock face, which was then utilized to model the excavation surface and derive the joint surfaces. Because joint surfaces have specific strikes and dip angles, the key blocks formed by these surfaces are deduced through iterative calculations, and the safety factor of each key block can be calculated accordingly. The model experiments confirmed the accuracy of the system's output in terms of the joint surface characteristics. By inputting the joint surface information, the calculated safety factors were compared with those from the existing commercial software, demonstrating stable calculation results within a 1% error margin.

• Journal of Korean Tunnelling and Underground Space Association
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• v.17 no.3
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• pp.393-401
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• 2015

In the construction of a TBM tunnel, it is very important to acquire accurate information of the excavated rock mass for an efficient and safe work. In this study, we developed the prediction system of TBM tunnel face ahead using probe drilling equipment and drilled hole imaging equipment to predict rock mass conditions of the tunnel face ahead. The prediction system consists of the probe drilling equipment, drilled hole imaging equipment and analysis software. The probe drilling equipment has been developed to be applicable to both non-coring and coring. Also the probe drilling equipment can obtain the drilling parameters such as feed pressure, torque pressure, rotation speed, drilling speed and so on. The drilling index is converted to the drilling index RMR through the correlation between a drilling index and core RMR. The developed system verification was carried out through a slope and tunnel field application. From the field application result, the non-coring is four times faster than a coring and the drilling index RMR and core RMR are similar in the distribution range. This system is expected to predict the rock mass conditions of the TBM tunnel face ahead very quickly and efficiently.

• Journal of the Korean Geosynthetics Society
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• v.9 no.1
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• pp.39-46
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• 2010

Recently, the effective use of closed waste landfill nearby urban areas has been demanded, because of the lack of the usable land. However, the reuse of closed landfill is needed an adequate stabilization of liner system. But most of these places are consisted of steep slope and hence it is necessary to use the geosynthetics liners in there. Liner system of waste landfills is an important facility which prevents leachate outgoing from the landfills and also groundwater infiltrating from surroundings into the landfills. During the waste disposal stage, differential settlement and tensile stress of the geosynthetic materials could occur due to impact load of trucks and dozers, waste loads and weak foundation soils. In this study, the tensile strength and tracer test were performed to evaluate the stability of geomembrane liner systems. Based on the tensile strength test result of in-situ geomembrane sample, the yield tensile strength maintain the suitable strength by specification and current law. However, according to the tracer test, the damage of geomembrane liner was detected on sanitary landfill section.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.6C
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• pp.385-393
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• 2006

Soil nailing is a reinforcement method used for stabilizing excavated walls or slopes. Due to its much advantages such as ease of construction and economical efficiency, use of soil nailing is increased. However, the soil nail has much disadvantages for use in urban area. The soil nail needs to be installed inevitably beyond private land boundary, which causes rent for use. For this reason, removable soil nailing system was developed. However, the removal rate of this system is just about 50￠¦70%. To resolve this problem, the Fiber Reinforced Plastic (FRP) soil nailing system which does not need to be removed and allows for the installation beyond private land, is developed. In this paper, through theoretical and experimental studies in laboratory and field such as prototype tests, pullout tests, we evaluate the stability and behavior characteristics of the FRP soil nailing system. And, numerical analyses using FLAC2D were performed with respect to various soil conditions, where prototype test for excavation wall and pullout tests were carried out. As a result of this study, the FRP soil nailing systems show similar behavior characteristics with those of removable soil nailing system. Finally, considering the serviceability and mechanical stability of FRP soil nailing systems, it is enough to be used as a good alternative of general soil nailing system.

• Tunnel and Underground Space
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• v.32 no.5
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• pp.285-297
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• 2022

We report results of Extended Leak-Off Test (XLOT) conducted in a large diameter borehole, which is drilled for installation of deep borehole geophysical monitoring system to monitor micro-earthquakes and fault behavior of major fault zones in the southeastern Korean Peninsula. The borehole was planned to secure a final diameter of 200 mm (or more) at a depth of ~1 km, with 12" diameter wellbore to intermediate depths, and 7-7/8" (~200 mm) to the bottom hole depth. We drilled first the 12" borehole to approximately 504 m deep and installed American Petroleum Institute standard 8-5/8" casing, then annulus between the casing and bedrock was fully cemented. XLOT was carried out for several purposes such as confirming casing and cementing integrity, measuring rock stress states. To that end, we drilled additional 4 m long open hole interval to directly inject water and pressurize into the rock mass using the upper API casings. During the XLOT, flow rates and interval pressures were recorded in real time. Based on the logs we tried to analyze hydraulic conductivity of the test interval.

• Journal of Korean Tunnelling and Underground Space Association
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• v.19 no.1
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• pp.11-27
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• 2017

The road network system of major domestic urban areas such as city of Seoul was rapidly developed and regionally expanded. In addition, many kinds of life-lines such as electrical cables, telephone cables, water&sewerage lines, heat&cold conduits and gas lines were needed in order for urban residents to live comfortably. Therefore, most of the life-lines were individually buried in underground and individually managed. The utility tunnel is defined as the urban planning facilities for commonly installing life-lines in the National Land Planning Act. Expectation effectiveness of urban utility tunnels is reducing repeated excavation of roads, improvement of urban landscape; road pavement durability; driving performance and traffic flow. It can also be expected that ensuring disaster safety for earthquakes and sinkholes, smart-grind and electric vehicle supply, rapid response to changes in future living environment and etc. Therefore, necessity of urban utility tunnels has recently increased. However, all of the constructed utility tunnels are cut-and-cover tunnels domestically, which is included in development of new-town areas. Since urban areas can not accommodate all buried life-lines, it is necessary to study the feasibility assessment system for utility tunnel by urban patterns and capacity optimization for urban utility tunnels. In this study, we break away from the new-town utility tunnels and suggest a quantitative assessment model based on the evaluation index for urban areas. In addition, we also develop a program that can implement a quantitative evaluation system by subdividing the feasibility assessment system of urban patterns. Ultimately, this study can contribute to be activated the urban utility tunnel.