Pore pressures in front of a slurry TBM, the influence of plastering mechanisms

Tunnelling induced groundwater flow is important to estimate the stability of the tunnel face as well as the time it will take to create and low permeable tunnel face. Infiltration of slurry or foam at the tunnel face has been tested in the past without considering the influence of groundwater flow, resulting in too high infiltration velocities and too fast plastering. The combination of groundwater flow and infiltration determines the velocity of the plastering at the tunnel face. What kind of plastering is achieved also depends on the slurry and the amount of sand in the slurry. Consequences will be discussed