Journal of Korean Tunnelling and Underground Space Association (한국터널지하공간학회 논문집)

Korean Tunnelling and Underground Space Association (한국터널지하공간학회)
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Numerical analyses using CFD on the pressure losses of the grout flow with variation of joint roughness and grout features

전산유동역학을 이용한 절리 거칠기 및 주입재 특성에 따른 그라우트 주입 시 압력 손실 해석

  • Sagong, Myung (Advanced Railroad Civil Engineering Division, Korea Railroad Research Institute) ;
  • Ryu, Sung-ha (Facility Team, Poongsan Corporation)
  • 사공명 (한국철도기술연구원 첨단궤도토목연구본부) ;
  • 류성하 (풍산 시설팀)
  • Received : 2018.08.23
  • Accepted : 2018.10.17
  • Published : 2018.11.30
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Abstract

Grouting for the rock joint is to strengthen the rock strata by infiltrating cement grout materials into the rock joints. Grouting is one of a field of study which is difficult to develop deterministic and quantitative design approach because of multiphase behaviors of grout materials and 3 dimensional features of rock joints. Therefore, GIN (Grouting Intensity Number) can be a good index with appropriate monitoring of pressure and volume of grout. In this paper, we investigate the effects of joint roughness (JRC) and rheology of cement material during the infiltration of cement grout material into rock joint through CFD (computational fluid dynamics) analyses. With rough joint surface and increase of WC ratio, the frictional resistance during the grouting increases. The results have been summarized with polynomial correlations.

암반 내 그라우팅은 불연속면 내부에 시멘트 그라우트재를 주입하여 주변지반을 강화하는 목적으로 사용된다. 현장에서 다상의 그라우트재의 주입 시 거동특성 및 주입경로인 3차원 절리면의 형태가 사전파악되지 않으므로 정량적인 설계가 어려운 분야중 하나이다. 따라서 현장에서의 그라우트 주입 거동특성을 나타내는 GIN (Grouting Intensity Number) 지표를 이용하여 주입 모니터링을 통해 적절한 시공관리를 수행하는 것이 최적이 방안이다. 본 논문에서는 그라우팅 주입 시 절리면의 거칠기 등급과 물시멘트(W/C)비에 따라 발생하는 압력의 손실을 전산유동해석을 수행하여 조사하였다. 절리면이 거칠수록 그리고 물시멘트비가 높을수록 주입 시 마찰저항은 크게 발생하였으며 해당 결과를 각 조건별 상관식으로 정리하였다.

Keywords

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Fig. 1. GIN envelope, target and zero flow path for the controlled grouting process

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Fig. 2. Schematic of grout injection

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Fig. 3 Topographic profile of a joint along x-axis

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Fig. 4. A correlation between standard deviation and Z2

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Fig. 5. Grid generation process (aperture = 0.3 mm)

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Fig. 6. Joint surface profile according to the JRC (aperture = 0.3 mm)

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Fig. 7. Herschel-Bulkley, Power-Law model of the shear stress and shear rate of change

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Fig. 8. The velocity profile of joint surface (W/C = 1, aperture = 0.3)

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Fig. 9. Pressure by position along the joint (kPa)

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Fig. 10. Variation of required injection pressure affected by W/C, aperture and JRC (kPa)

Table 1 A correlation between Standard deviation, Z2 and JRC

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Table 2. Grout material properties

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Table 3. Boundary condition

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Table 4. Required pressures for a constant grout injection of 3 l/min with different joint apertures and roughness (kPa)

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Table 4. Correlations of Kp with aperture and JRC

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Table 4. Correlations of Kp with aperture and JRC (continue)

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