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Geomechanics and Engineering
  Volume 21, Number 2, April25 2020, pages 165-170

Change of groundwater inflow by cutoff grouting thickness and permeability coefficient
Youngsang Kim and Joon-Shik Moon

    The groundwater during tunnel excavation not only affects the stability of the tunnel and constructability but also causes the subsidence of the upper ground due to the lowering of groundwater. Generally, the cutoff grouting is applied as a countermeasure to reduce the groundwater inflow during tunnel excavation, and the cutoff grouting is often applied in the range of plastic zone around the tunnel. However, grouting in the plastic zone is only appropriate for ground reinforcement purposes, and guidelines for the application range of cutoff grouting and the targeted permeability coefficient of the grouting zone are required. In this study, the relationship between groundwater inflow into tunnel and application range of cutoff grouting and permeability coefficient is proposed and compared with numerical analysis results. It was found that grouting with tunnel radius thickness is appropriate to reduce the groundwater inflows effectively. More than 90% reduction in groundwater inflow can be achieved when the annular area of the tunnel radius thickness is grouted with a permeability reduction ratio of 1/50~1/200.
Key Words
    cutoff grouting; grouting zone; groundwater inflow; tunnel
Youngsang Kim: Department of Civil Engineering, Chonnam National University, Gwangju 61186, Republic of Korea

Joon-Shik Moon: Department of Civil Engineering, Kyungpook National University, Daegu 41566, Republic of Korea

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