• Title, Summary, Keyword: Shotcrete

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A Study on the Watertightness of Shotcrete with Watertightness Materials (수밀성 재료에 의한 숏크리트의 수밀성에 관한 연구)

  • Kang, Hyun-Ju;Song, Myong-Shin;Lee, Sang-Kook
    • Journal of the Korean Ceramic Society
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    • v.45 no.6
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    • pp.350-357
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    • 2008
  • The use of shotcrete-sprayed concrete for the support of underground excavations was pioneered by the civil engineering. Now, for the nuclear wastes disposal plant in our country, watertightness of shotcrete is one of the very important properties. This study evaluated the watertightness of shotcrete using cement mineral accelerator with watertightness materials for the long-term watertightness. In this study, for improvement of watertightness of shotcrete, it used two types of obtainable at a store. Watertightness tests of shotcrete were performed the water absorption coefficient, permeability, porosity and hydrates variation. In a shotcrete containing watertightness materials, watertightness of shotcrete was improved about $15%{\sim}65%$ rather than plain shotcrete.

Evaluation of Physical Performance of High-Strength.High Waterproof Ready-mixed Shotcrete using Powdered Polymer Dispersion (분말형 폴리머 혼화제를 적용한 고강도.고차수성 레디믹스트 숏크리트의 물리적 성능 평가)

  • Ma, Sang-Joon;Choi, Hee-Sup;Lee, Heung-Soo
    • Proceedings of the Korea Concrete Institute Conference
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    • pp.337-340
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    • 2008
  • As the Ready-mixed Shotcrete using Powdered Polymer Dispersion, Shotcrete Matrix as totally shotcrete gel that a part of second binder in Shotcrete materials is dense. Also, Ready-mixed Shotcrete is showed the decreasing Rebound and rising Durability. Therefore, it is possible that Ready-mixed Shotcrete for High-Strength and High-Waterproof can apply to the Powdered Polymer Dispersion.

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Multiple Polyamide Fiber Reinforced Shotcrete for Railway Tunnel Structure (철도 터널 구조물 시공을 위한 다발형 폴리아미드섬유 보강 숏크리트)

  • Jeon, Joong-Kyu;Chung, Jae-Min;Yoon, Ji-Hyun;Jeon, Chan-Ki
    • Proceedings of the KSR Conference
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    • pp.1214-1219
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    • 2011
  • Fiber reinforced shotcrete began to be used in tunnel constructions because it facilitates and expedites the construction process, and improves reinforcement properties. As one of the most widely used forms of shotcrete used in tunneling, steel fiber reinforced shotcrete offers excellent strength and ductility and allows quick reinforcement. However, steel fibers tend to lump together in cement matrix, and low levels of water and acid resistance cause corrosion in steel fiber, resulting in cracks and delamination. In particular, rebound and backlash of steel fiber is significantly increased during steel fiber reinforced shotcrete construction, compromising the flexural toughness and quality of shotcrete. In order to resolve the problems associated with steel fiber reinforced shotcrete and improve the application, durability, and cost-effectiveness of shotcrete, this paper proposes methods for manufacturing and constructing tunnels with multiple polyamide fiber reinforced shotcrete. We performed experiments to evaluate the performance of the proposed shotcrete, and the experimental results indicate that the multiple polyamide fiber reinforced shotcrete proposed in this paper offers outstanding performance that meets various construction design criteria.

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An Experimental Study on the Effect of Accelerator and Chemical Admixture Type for the Durability of Shotcrete (급결제 및 혼화제 종류가 숏크리트 내구성에 미치는 영향에 관한 연구)

  • 백신원;권소진;이영수;김의성;신용석
    • Journal of the Korean Society of Safety
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    • v.18 no.3
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    • pp.109-113
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    • 2003
  • Concrete and shotcrete should withstand the conditions for which they have been designed, without deterioration, over a period of years. But connote and shotcrete are being deteriorated according to aging by internal and external causes. Recently, many studies on the durability of concrete have been conducted But the durability of shotcrete is rarely studied. So, in this study, chloride ion penetration test freeze and thaw test neutralization test were conducted to examine the durability characteristics of shotcrete with several accelerator and chemical admixture types. These results indicate that shotcrete with allah free accelerator and with superplasticizer are durable. Therefore, the present study provides a fm base to make high performance shotcrete.

Development of High Performance Shotcrete for Permanent Shotcrete Tunnel Linings (III) (Field Test of Wet-mixed Shotcrete with Powder Types Cement Mineral Accelerator) (Permanent Shotcrete Tunnel Linings 구축을 위한 고성능 숏크리트 개발(III)(시멘트 광물계 분말형 급결제를 사용한 습식숏크리트 현장시험시공))

  • 박해균;이명섭;김재권;김용하
    • Proceedings of the Korea Concrete Institute Conference
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    • pp.609-617
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    • 2003
  • The use of Shotcrete(Sprayed concrete) for the support of underground excavations was pioneered by the Civil engineering industry. Permanent shotcrete tunnel linings such as Single-shell, NMT(Norwegian Method of Tunnelling) have been constructed in many countries for reducing construction time and lowering construction costs instead of conventional in-situ concrete linings. Among essential technologies for successful application of Permanent Shotcrete Linings, high performance shotcrete having high strength, high durability, better pumpability has to be developed in advance. This paper presents the ideas and the first field test results of wet-mixed Steel Fiber Reinforced Shotcrete(SFRS) with powder types cement mineral accelerator. From the results, wet-mix SFRS with powdered accelerator exhibited good early strength improvement and less rebound ratio compared to the ordinary accelerator.

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A Study on the Strength Characteristics and Rebound Ratio with Respect to Injection Pressure of Shotcrete (숏크리트의 강도 특성과 분사압력에 대한 리바운드율 연구)

  • Jeon, Jun Tai;Moon, In Gi;Lee, Yang Kyu
    • Journal of The Korean Society of Civil Engineers
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    • v.39 no.1
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    • pp.115-122
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    • 2019
  • Steel Fiber Reinforced Wet-type Shotcrete improves the quality and stabilizes the tunnel by increasing the shear strength of the natural ground by constructing the concrete which attaches the fresh concrete to the predetermined position from the nozzle. The Steel Fiber Reinforced Wet-type Shotcrete improves and reinforces the strength and dynamic behavior characteristics of concrete to suppress the generation and growth of local cracks by increasing the tensile resistance ability. In addition, Steel Fiber Reinforced Wet-type Shotcrete is a shotcrete that improves tensile strength, bending strength, and crack resistance by dispersing discontinuous short steel fibers evenly in concrete. In this study, compressive strength test and bending strength test of shotcrete of NATM tunnel were measured and rebound reduction rate was measured by varying shotcrete putting pressure to 900 RPM, 1,000 RPM, and 1,100 RPM. Therefore, the data that can be applied to domestic NATM tunnel construction are presented.

Suggestion for the improvement of the field measurements on the shotcrete lining (터널 숏크리트 계측의 개선방안)

  • Kim, Hak-Joon;Park, Si-Hyun;Bae, Gyu-Jin
    • Journal of Korean Tunnelling and Underground Space Association
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    • v.12 no.2
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    • pp.177-192
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    • 2010
  • The field measurements on the shotcrete lining are usually performed during the tunnel construction. However, the credibility of the measurements is not certain because of the non-stress related strains occurring in the shotcrete, the uncertainty of the deformation modulus of the shotcrete, and the intrinsic difficulties involved in the strain measurements in the shotcrete. The problem related to the field measurements on the shotcrete is investigated using the review of the previous studies and the field measurement performed for this study. A method for the correction of stress measurements at the shotcrete lining, considering the non-stress related strains, is suggested using the literature review and the actual measurements obtained from the non-stress shotcretes. The deformation modulus used for the calculation of the stress acting on the shotcrete is also suggested.

A study on Actual Quantity of Shotcrete Sprayed in a NATM tunnel (NATM 산악터널의 숏크리트 투입율에 관한 연구)

  • Lee, Cheol-Ju;Kim, Sung-Yun;Kim, Dong-Gun;Yoo, Nam-Jae
    • Journal of Industrial Technology
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    • v.29 no.B
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    • pp.57-64
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    • 2009
  • This study has analysed actual overbreak, shotcrete rebound and the ratio between the actual quantity of shotcrete to designed shotcrete measured during a NATM tunnel construction. The measured shotcrete rebound was about 7.2% in average which was about half the allowable rebound (15%), showing shotcrete spraying was performed well. Based on the measurement of excavated tunnel shape, average overbreak was about 28.5cm after tunnel excavation by drill and blasting method. This was about 260% of allowable overbreak. In addition, due to the rebound and overbreak actual amount of shotcrete used in the tunnelling work was about 116.5 % of the designed value. According to the field measurement the ratio of actual shotcrete to designed value showed some relation with standard support pattern, but the size of overbreak did not show the correlation with standard support pattern. Hence current design specifications stating the size of overbreak based entirely on standard support pattern should perhaps be reestablished. The insight into the design guideline regarding overbreak and shotcrete.

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Numerical Study for Tunnel Shotcrete Lining Operated Stress Measurement Techique Development During a Construction (시공중 터널 숏크리트 라이닝 작용응력 측정기법 개발을 위한 수치해석적 연구)

  • Shin, Hyu-Seong;Kim, Dong-Gyou;Jung, Yong-Su;Hwang, Jae-Hong;Bae, Gyu-Jin
    • Proceedings of the Korean Geotechical Society Conference
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    • pp.754-761
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    • 2008
  • In general, stress measurement of existent shotcrete lining be used by pressure cells. but, measuring instrument is lost by high pressure at shotcrete lining construction and pressure cell's measurement value have to low believability by natural conditions like curing temperature. In this study, proposed techniques to measure without utilizing sensitive stress sensor in natural condition at point that want stress of shotcrete lining after shotcrete lining construction. Executed numerical analysis to forecast stress level that interact in tunnel shotcrete lining, measured strain of hole by load action through hole in shotcrete lining. 3D FEM(finite element method) is enforced through various parameters curing time of shotcrete lining, thickness, load condition. Different model cases applied by parametic study. As analysis result, it could grasp development possibility of method that propose this time because it could examine corelation with strain by near hole of shotcrete lining and stress about load condition.

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