• Title/Summary/Keyword: Rock tunnel

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Potential repository domain for A-KRS at KURT facility site (KURT 부지 조건에서 A-KRS 입지 영역 도출)

  • Kim, Kyung-Su;Park, Kyung-Woo;Kim, Geon-Young;Choi, Heui-Joo
    • Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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    • v.10 no.3
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    • pp.151-159
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    • 2012
  • The potential repository domains for A-KRS (Advanced Korean Reference Disposal System for High Level Wastes) in geological characteristics of KURT (KAERI Underground Research Tunnel) facility site were proposed to develop a repository system design and to perform the safety assessment. The host rock of KURT facility site is one of major Mesozoic plutonic rocks in Korean peninsula, two-mica granite, which was influenced by hydrothermal alteration. The topographical features control the flow lines of surface and groundwater toward south-easterly and all waters discharge to Geum River. Fracture zones distributed in study site are classified into order 2 magnitude and their dominant orientations are N-S and E-W strike. From the geological features and fracture zones, the potential repository domains for A-KRS were determined spatially based on the following conditions: (1) fracture zone must not cross the repository; and (2) the repository must stay away from the fracture zones greater than 50 m. The western region of the fracture zones in the N-S direction with a depth below 200 m from the surface was sufficient for A-KRS repository. Because most of the fracture zones in N-S direction were inclined toward the east, we expected to find a homogeneous rock mass in the western region rather than in the eastern region. The lower left domain of potential domains has more suitable geological and hydrogeological conditions for A-KRS repository.

Experimental and Numerical Studies on Application of Industrial Explosives to Explosive Welding, Explosive Forming, Shock Powder Consolidation (산업용 폭약을 이용한 폭발용접, 폭발성형과 충격분말고화에 관한 실험 및 수치해석적 연구)

  • Kim, Young-Kook;Kang, Seong-Seung;Cho, Sang-Ho
    • Tunnel and Underground Space
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    • v.22 no.1
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    • pp.69-76
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    • 2012
  • Theoretical backgrounds on the experimental methods of explosive welding, explosive forming and shock consolidation of powders are introduced. Explosive welding experiments of titanium (Ti) and stainless steel (SUS 304) plate were carried out. It was revealed that a series of waves of metal jet are generated in the contact surface between both materials; and that the optimal collision velocity and collision angle is about 2,100~2,800 m/s and $15{\sim}20^{\circ}$, respectively. Also, explosive forming experiments of Al plate were performed and compared to a conventional press forming method. The results confirmed that the shock-loaded Al plate has a larger curvature deformation than those made using conventional press forming. For shock consolidation of powders, the propagation behaviors of a detonation wave and underwater shock wave generated by explosion of an explosive are investigated by means of numerical calculation. The results revealed that the generation and convergence of reflected waves occur at the wall and center position of water column, and also the peak pressure of the converged reflected waves was 20 GPa which exceeds the detonation pressure. As results from the consolidation experiments of metal/ceramic powders ($Fe_{11.2}La_2O_3Co_{0.7}Si_{1.1}$), shock-consolidated $Fe_{11.2}La_2O_3Co_{0.7}Si_{1.1}$ bulk without cracks was successfully obtained by adapting the suggested water container and strong bonding between powder particles was confirmed through microscopic observations.

Effect of Steel-fiber Distribution on Flexural Strength and Toughness of Shotcrete-mimicked Concrete Specimen (숏크리트 모사 콘크리트 공시체에 혼합된 강섬유의 분산도가 휨강도 및 인성에 미치는 영향)

  • Park, Sung-Sik;Kim, Sang-Jung
    • Journal of the Korean Geotechnical Society
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    • v.29 no.6
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    • pp.53-62
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    • 2013
  • A 5-20 cm thick shocrete has been routinely constructed for NATM tunneling method to stabilize and confine the excavated rock of tunnel construction site. A $40kg/m^3$ of steel fibers are usually mixed into such shotcrete but these steel fibers may not be evenly distributed depending on shotcrete machines, mixing ratios and excavated rock conditions. In this study, square column shotcrete-mimicked concrete specimens of $15cm{\times}15cm{\times}55cm$ were prepared with 5 equal layers and 5 or 20% cement ratio. The specimens were prepared with different reinforced-patterns: non-reinforced, middle layer-reinforced, 1, 3, and 5 layers-reinforced, or all layers reinforced. The specimens were air-cured for 7 days and tested for flexural strength. The influence of steel-fiber distribution on flexural strength and toughness of shotcrete-mimicked concrete specimens was investigated. In the case of a specimen with cement ratio of 20%, a flexural strength increased as a number of fiber-reinforced layer increased. The flexural strength of one-layer reinforced specimen showed 20% less than that of evenly fiber-distributed specimen. On the other hand, a specimen with cement ratio of 5% decreased as the number of fiber-reinforced layers increased. A toughness index increased as the number of fiber-reinforced layers increased, regardless of cement ratios. The toughness index of evenly fiber-distributed specimen showed 2-3 times as large as that of one-layer reinforced specimen.

Study of Blast Ground Vibration & Noise Measurements In-situ and Effect Analysis for Numerical Analysis, Rational Blasting Design at an Eel Farm (양만장의 발파 진동소음 현장측정과 수치해석을 통한 영향검토 및 합리적인 발파설계 연구)

  • Lee Song;Kim Sung-Ku;Rhee Yong-Ho
    • Tunnel and Underground Space
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    • v.16 no.2 s.61
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    • pp.179-188
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    • 2006
  • The vibration or/and noise generated by blast operations might cause not only structural damage to properties but mentally also to humans and animals. For that reason, maximum permitted vibration and noise levels are set by sensitivities of structures and they are used for the management of blast vibration. It is known that the fish lived in water are more sensitive to vibration than land animals, and thus the adverse impact of the blasting on fish farms should be very concerned. This study investigated the vibration and noise levels at a large eel farm located some 840 meters of the blasting site through the large real-scale experiments of blastings, prior to conducting the actual blasting. As a result, it was found that the noise met the requirement to be within maximum permitted level, while the ground vibration exceeded the permitted vibration. Accordingly, the impact of the excess vibration was investigated by an existing empirical method and verified by a new three dimensional numerical analysis. In this study, such an inspection process was briefly described, and a method was suggested for the examination of possible adverse effects from blasting on vibration-sensitive structures like the eel farm. The study also introduced a design method that controls the blast effects - ground vibration and noise.

Fracture Toughness Evaluation and Influence Parameter Analysis by Numerical Simulation of Brazilian Test (Brazilian 시험의 수치해석 시뮬레이션을 통한 파괴인성 산정 및 영향변수 분석)

  • Synn, Joong-Ho;Park, Chan;Shin, Hee-Soon;Chung, Yong-Bok;Lee, Hi-Keun
    • Tunnel and Underground Space
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    • v.10 no.3
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    • pp.320-328
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    • 2000
  • The numerical simulation of Brazilian fracture toughness test is carried out using PFC code and the influence parameters are analyzed such as shape of loading plane, size of Brazilian disc and unit particle of model, loading angle and loading rate. The flattened Brazilian disc is adopted for applying uniform load. The range of loading angle(2$\alpha$) necessary to induce the tensile crack at disc center and to obtain the load-displacement curve giving the critical load for the stable crack propagation is shown as 20°∼40°. In condition that the loading angle is 20°, the mode-I fracture toughness is evaluated almost constant in the range of particle size less than 1 mm and loading rate less than 0.01㎜/s. This range of influence parameters seems appropriate condition for the tensile crack initiation at disc center and the control of stable crack propagation, which can give the reliance in evaluation of fracture toughness by Brazilian test.

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Experimental Study on Source Locating Technique for Transversely Isotropic Media (횡등방성 매질의 음원추적기법에 대한 실험적 연구)

  • Choi, Seung-Beum;Jeon, Seokwon
    • Tunnel and Underground Space
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    • v.25 no.1
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    • pp.56-67
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    • 2015
  • In this study, a source locating technique applicable to transversely isotropic media was developed. Wave velocity anisotropy was considered based on the partition approximation method, which simply enabled AE source locating. Sets of P wave arrival time were decided by the two-step AIC algorithm and they were later used to locate the AE sources when having the least error compared with the partitioned elements. In order to validate the technique, pencil lead break test on artificial transversely isotropic mortar specimen was carried out. Defining the absolute error as the distance between the pencil lead break point and the located point, 1.60 mm ~ 14.46 mm of range and 8.57 mm of average were estimated therefore it was regarded as thought to be 'acceptable' considering the size of the specimen and the AE sensors. Comparing each absolute error under different threshold levels, results showed small discrepancies therefore this technique was hardly affected by background noise. Absolute error could be decomposed into each coordinate axis error and through it, effect of AE sensor position could be understood so if optimum sensor position was able to be decided, one could get more precise outcome.

Changes on Physical Property of Ilmenite due to Microorganism (미생물에 의한 티탄철석의 물리적 특성 변화)

  • Park, Young Ho;Kang, Dae Wan;Kang, Seong-Seung
    • Tunnel and Underground Space
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    • v.22 no.5
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    • pp.321-329
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    • 2012
  • Laboratory tests for measuring absorption, porosity, P-wave velocity and uniaxial compressive strength (UCS) were performed to examine weathering characteristics of ilmenite by microorganism. Physical property changes were quantitatively estimated with comparing culture period on the condition of abiotic oxidation without microorganism and biooxidation with microorganism. As a result, the measured pH during 45 days was distributed in the range from 3.82 to 4.26, on the other hand, biooxidation showed the range from 2.20 to 2.57. The measured absorption according to microorganism and culture period represented 0.052% at final stage in the case of abiotic oxidation and 0.073% in the case of biooxidation. Porosity showed 0.206% at final stage in the case of abiotic oxidation and 0.281% in the case of biooxidation. In general, the values by biooxidation showed higher than that by abiotic oxidation. Change range of P-wave velocity with culture period showed that the measured value as 1410 m/s at final stage in the case of biooxidation was lower than 1886 m/s of that in the case of abiotic oxidation. The UCS was decreased with increasing culture period in all specimens and represented 241.1 MPa at final stage in the case of abiotic oxidation and 140.0 MPa in the case of bioxidation. In conclusion, it implies that influence of physical property on ilmenite by biooxidation related with microorganism was larger than that by abiotic oxidation.

Creation of Vector Network Data with Considering Terrain Gradient for Analyzing Optimal Haulage Routes of Dump Trucks in Open Pit Mines (노천광산 덤프트럭의 최적 운반경로 분석을 위한 지형경사가 고려된 벡터 네트워크 자료의 생성 방법)

  • Park, Boyoung;Choi, Yosoon;Park, Han-Su
    • Tunnel and Underground Space
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    • v.23 no.5
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    • pp.353-361
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    • 2013
  • Previous studies for analyzing optimal haulage routes of dump trucks in open pit mines mostly used raster data. However, the raster data has several problems in performing optimal route analyses: (1) the jagged appearance of haulage roads according the cell resolution often causes overestimation of the travel cost; (2) it difficult to trace the topological relationships among haulage roads. These problems can be eliminated by using vector network data, however a new method is required to reflect the performance characteristics of a dump truck according to terrain gradient changes. This study presents a new method to create vector network data with the consideration of terrain gradient for analyzing optimal haulage routes of dump trucks in open pit mines. It consists of four procedures: (a) creating digital elevation models, (b) digitizing haulage road networks, (c) calculating the terrain gradient of haulage roads, and (d) calculating the average speed and travel time of a dump truck along haulage roads. A simple case study at the Roto South pit in the Pasir open pit coal mine, Indonesia is also presented to provide proof that the proposed method is easily compatible to ArcGIS Network Analyst software and is effective in finding optimal haulage routes of dump trucks with considering terrain gradient in open pit mines.

A Study on Thermodynamic Natural Ventilation Analysis by the Field Survey of Underground Mines in Korea (현장실측을 통한 국내 일반광의 열역학적 자연통기력 연구)

  • Yu, Yeong-Seok;Roh, Jang-Hoon;Kim, Jin
    • Tunnel and Underground Space
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    • v.23 no.4
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    • pp.288-296
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    • 2013
  • In this study, a total of 13 mines were finally selected as study subjects and field measurements were conducted. Thereafter, calculations of thermodynamic natural ventilation were attempted using spread sheets and solutions for natural ventilation of mine types with multiple vertical shafts were obtained. Based on the results, natural ventilation of each mine was quantified. In addition, changes in natural ventilation energy (NVE) and natural ventilation pressure (NVP) were estimated assuming mine deepening and the resultant values were applied to mine conditions to observe changes in flow rates. Natural ventilation pressure in domestic mines is generally calculated to be in a range of 5 Pa~300 Pa. Although NVP increases as the depth increases, resistance also increases. Therefore, as the depth increases, flow rates show a tendency of converging on a certain value because of the relationship between NVP and mine resistance. Natural ventilation using shafts with depth differences is effective up to depths of 200~300 m. However, flow rate change rates resulting from NVP are small at depths deeper than approximately 200~300 m. Therefore, if a mine is deepened over 300 m, NVP will become insufficient and thus additional pressure obtained through mechanical ventilation will be necessary.

A Study on the Optimal Installation of Ducted Fan Ventilation System in Long Mine Airways - Focused on the Wall Separation Distance and the Gap Length between Ducts (장대 광산갱도내 풍관 접속 통기선풍기 최적 설치 방안연구 - 벽면과 풍관간의 이격거리 중심으로)

  • Lee, Chang Woo;Nguyen, Van Duc
    • Tunnel and Underground Space
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    • v.27 no.1
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    • pp.12-25
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    • 2017
  • In local underground mines heavily depending on the natural ventilation, ducted fan auxiliary ventilation system is strongly recommended instead of the total mine ventilation system requiring large capital and operating costs. Optimizing the installation of ducted fans in series in long large-opening mines is required to assure the economy and efficiency of the ventilation system. The two most critical design parameters for optimization are the wall separation distance and gap length between adjoining ducts. This study aims at deriving the optimal values for those two parameters concerning the economic and environmental aspects through the extensive CFD analysis, which minimizes pressure loss, leakage and entrainment of the contaminated air in the gap space. The ranges of the wall separation distance and gap length for study are selected by taking into consideration the existing recommendations and guidelines. The ultimate goal is to optimize the auxiliary ventilation system using ducted fans in series to provide a reliable and efficient solution to maintain clean and safe workplace environment in local long underground mines.