• Title, Summary, Keyword: 숏크리트

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An Experimental Study on the Silica Fume and Steel Fiber Reinforced Shotcrete (실리카흄 및 강섬유보강 숏크리트의 실험적 연구)

  • 오병환;박칠림;백신원;장성욱
    • Proceedings of the Korea Concrete Institute Conference
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    • pp.119-124
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    • 1992
  • 최근들어 고속도로, 고속철도,지하철 등의 건설이 급격히 증가함에 따라 터널의 건설이 늘어나고 있다. 이러한 터널등의 건설에서 필수적으로 따르는 것이 숏크리트의 시공이며 이러한 숏크리트의 시공은 앞으로 더욱 증가할 추세에 있다. 그러나 숏크리트의 광범위한 시공에도 불구하고 현재 여러 가지 문제점을 내포하고 있는 것이 사실이다. 따라서 본 연구에서는 우리나라 현행 숏크리트의 현황과 문제점을 도출하여 성능개선을 위한 최적 배합을 도출하고 고품질의 숏크리트 시공을 위하여 실리카퓸 숏크리트의 개발 및 적용과 인성(Toughness)과 연성(Ductility)을 대폭 증가시키고 시공속도를 빠르게 하여 안전성과 함께 경제성을 확보할 수 있는 강섬유보강 숏크리트의 개발 및 적용에 대한 연구를 집중적을 수행하였다. 본 연구로부터 숏크리트의 최적 배합을 도출하였고 강도와 내구성을 함께 증가시키고 리바운드율을 대폭 감소시킬 수 있는 실리카퓸 숏크리트를 개발하였다. 또한 wiremesh를 대체할 수 있는 강섬유보강 숏크리트를 개발하여 실내시험 및 현장 적용성 시험을 수행하였다.

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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.

Case Studies for the Stress Measurements on the Shotcrete Tunnel Lining (터널에서의 숏크리트 응력 측정 사례 연구)

  • Kim, Hak Joon;Kim, Mi-Ran
    • The Journal of Engineering Geology
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    • v.24 no.1
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    • pp.81-89
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    • 2014
  • Stress measurements of shotcrete lining were performed to evaluate the stability of the primary lining and to determine the thickness and the construction timing of the secondary lining. The current situation of stress measurements of shotcrete and problems related to judging the safety of shotcrete linings are presented, based on the results of several case studies. An improved method of performing stress measurements on shotcrete lining is also presented. In evaluating the safety of shotcrete lining, the use of absolute values of measured stresses would improve the reliability of the measurements.

Recent Issues in the Design and Construction of High-Performance Shotcrete Lining (고성능 숏크리트 라이닝의 설계 및 시공기술 분석)

  • 배규진;이석원;박해균;이명섭;김재권;장수호
    • Tunnel and Underground Space
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    • v.14 no.1
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    • pp.1-15
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    • 2004
  • The development of high-performance shotcrete lining is essential in improving the long-term durability of tunnels and in introducing single-shell tunnelling methods, where shotcrete as well as rockbolts are used as permanent support members. In this paper, new and advanced admixtures to improve shotcrete performance are introduced. In addition, requirements for mechanical properties as well as test items for quality control of shotcrete are summarized. A case study on the application of the pneumatic pin penetration test which can estimate compressive strength of shotcrete more easily and quickly is also illustrated. Previous studies to analyze the behaviors of shotcrete lining by considering its transient hardening and to carry out the sensitivity analysis of the design parameters of shotcrete lining are discussed to give fundamental concepts on rock-support interactions. Representative single-shell tunnelling methods where high-performance shotcrete lining is applied as a permanent support are also introduced.

3-Dimensional numerical analysis on support performance of early-high-strength shotcrete (3차원 수치해석을 이용한 조기고강도 숏크리트 지보성능 분석)

  • Kim, Jong-Uk;Kim, Jung-Joo;Cho, Young-Jae;Yoo, Han-Kyu
    • Journal of Korean Tunnelling and Underground Space Association
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    • v.16 no.5
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    • pp.459-470
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    • 2014
  • Now-a-days, the trend in constructing tunnels is to build more deeper, more longer tunnels of greater cross-sections. That's why, the demand of "Early-high-strength shotcrete" is very high because of their advantage of attaining higher strength immediately after excavation, which controls the ground subsidence. So, this study reveals the supporting phenomena of early-high-strength shotcrete, using three-dimensional numerical analysis. The crux of this study can be applied practically in construction sites also. Support Performance of two different qualities of shotcrete was checked out, by keeping the general shotcrete's thickness constant and comparing it with early-high-strength shotcrete's thickness decreasing it gradually in five steps, and analysing/comparing the support performance in all cases. Effect of using early-high-strength shotcrete was analysed to save the cost of steel sets, which are widely used for supporting the ground before the hardening of general shotcrete. The results of numerical analysis on the performance of early-high-strength shotcrete show that, it behaves more effectively under worse ground conditions and it can support the ground more conveniently than steel sets, before the shotcrete is hardened.

Experimental Construction of Polyamide Fiber Reinforced Shotcrete Technology (다발형 폴리아미드섬유 보강 숏크리트 현장 적용성 평가)

  • Yoon, Ji-Hyun;Jeon, Joong-Kyu;Jeon, Chan-Ki;Lee, Soo-Choul
    • Journal of the Korean Recycled Construction Resources Institute
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    • v.7 no.2
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    • pp.78-83
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    • 2012
  • Steel fiber reinforced shotcrete in tunneling construction has some problems in terms of constructability, durability and lots of rebound wastage. In order to resolve these problems, this pater proposes polyamide fiber reinforced shotcrete technology. And this paper presents the results of experimental construction of the polyamide fiber reinforced shotcrete technology. The results of the study are as follows. 1. The polyamide fiber reinforced shotcrete suggested in this paper shows outstanding mechanical performance that meets various Korean tunnel construction design criteria. 2. In addition, the results of experimental constructions show that the polyamide fiber reinforced shotcrete creates less rebound and wasted product than the steel fiber reinforced shotcrete. Based on the above results, it is concluded that the polyamide fiber reinforced shotcrete technology can be used as economical and environmentally friendly construction of tunnel.

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Flexural Behavior Evaluation of Two Types Fiber Reinforced Shotcrete using Round Panel Test (원형패널 시험을 활용한 두 종류 섬유 보강 숏크리트의 휨거동 평가)

  • Jeon, Chanki;Jeon, Joongkyu
    • Journal of the Society of Disaster Information
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    • v.11 no.4
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    • pp.607-614
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    • 2015
  • This study evaluated the flexural performance of steel and PP fiber reinfroced shotcrete using round panel test according to ASTM that can consider the actual stress of fiber reinforced shotcrete in tunnel and under ground structures. The results of round panel test are converted to the square panel test results according to the EFNARC. The energy absorptions of each fiber reinforced shotcrete were classified according to the EFNARC toughness classification. Test results show that the PP fiber reinforced shotcrete has better flexural performance compared with the steel fiber reinforced shotcrete.

Evaluation of bonding state of shotcrete lining using nondestructive testing methods - experimental analysis (비파괴 시험 기법을 이용한 숏크리트 배면 접착상태 평가에 관한 실험적 연구)

  • Song, Ki-Il;Cho, Gye-Chun;Chang, Seok-Bue;Hong, Eun-Soo
    • Journal of Korean Tunnelling and Underground Space Association
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    • v.11 no.1
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    • pp.71-83
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    • 2009
  • Shotcrete is an important primary support for tunnelling in rock. The quality control of shotcrete is a core issue in the safe construction and maintenance of tunnels. Although shotcrete may be applied well initially onto excavated rock surfaces, it is affected by blasting, rock deformation and shrinkage and can debond from the excavated surface, causing problems such as corrosion, buckling, fracturing and the creation of internal voids. This study suggests an effective non-destructive evaluation method of the tunnel shotcrete bonding state applied onto hard rocks using the impact-echo (IE) method and ground penetration radar (GPR). To verify previous numerical simulation results, experimental study carried out. Generally, the bonding state of shotcrete can be classified into void, debonded, and fully bonded. In the laboratory, three different bonding conditions were modeled. The signals obtained from the experimental IE tests were analyzed at the time domain, frequency domain, and time-frequency domain (i.e., the Short- Time Fourier transform). For all cases in the analyses, the experimental test results were in good agreement with the previous numerical simulation results, verifying this approach. Both the numerical and experimental results suggest that the bonding state of shotcrete can be evaluated through changes in the resonance frequency and geometric damping ratio in a frequency domain analysis, and through changes in the contour shape and correlation coefficient in a time-frequency analysis: as the bonding state worsens in hard rock condition, the autospectral density increases, the geometric damping ratio decreases, and the contour shape in the time-frequency domain has a long tail parallel to the time axis. The correlation coefficient can be effectively applied for a quantitative evaluation of bonding state of tunnel shotcrete. Finally, the bonding state of shotcrete can be successfully evaluated based on the process suggested in this study.

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Analysis of the peak particle velocity and the bonding state of shotcrete induced by the tunnel blasting (발파시 터널 숏크리트의 최대입자속도와 부착상태평가 분석)

  • Hong, Eui-Joon;Chang, Seok-Bue;Song, Ki-Il;Cho, Gye-Chun
    • Journal of Korean Tunnelling and Underground Space Association
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    • v.12 no.3
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    • pp.247-255
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    • 2010
  • Bonding strength of shotcrete is a significant influential factor which plays the role of collapse prevention of tunnel crown and of debonding prevention of shotcrete induced by the blasting vibration. Thus, the evaluation of the shotcrete bonding state is one of the core components for shotcrete quality control. In this study, the peak particle velocities induced by blasting were measured on the shotcrete in a tunnel construction site and its effect on the bonding state of shotcrete is investigated. Drilling and blasting technique was used for the excavation of intersection tunnel connecting the main tunnel with the service tunnel. Blast-induced vibrations were monitored at some points of the main tunnel and the service tunnel. The shotcrete bonding state was evaluated by using impact-echo test coupled with the time-frequency domain analysis which is called short-time Fourier transformation. Analysis results of blast-induced vibrations and the time-frequency domain impact-echo signals showed that the blasting condition applied to the excavation of intersection tunnel hardly affects on the tunnel shotcrete bonding state. The general blasting practice in Korea was evaluated to have a minor negative impact on shotcrete quality.

A Study on Effect of Shotcrete Adhesive Strength on Large Section Rock Tunnel Stability (대단면 암반터널의 안정성에 미치는 숏크리트 부착강도의 영향에 관한 연구)

  • Chang, Seok-Bue;Hong, Eui-Joon;Moon, Sang-Jo
    • Journal of Korean Tunnelling and Underground Space Association
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    • v.7 no.4
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    • pp.305-311
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    • 2005
  • Shotcrete adhesive strength in large section tunnels in jointed rock masses plays an important role in preventing rock block from falling and shotcrete debonding due to blasting vibration. Nevertheless, it has not been considered as a major factor such as shotcrete compressive strength in design and construction. For this reason, the purpose of this study is to analyze the effect on shotcrete adhesive strength for large-sectioned tunnels. First, the parametric study using numerical model similar to Holmgren's punch-loaded test was executed for various range of adhesive strength. It shows that the shotcrete bearing capacity is linearly proportioned to the adhesive strength between shotcrete layer and blocks. And then, distinct element analysis of a jointed rock tunnel for an adhesive strength of 1 MPa and a conventional fully-bonded condition between the shotcrete layer and the excavation face was compared in order to evaluate the effect of the shotcrete adhesive strength.

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