Simulation of groundwater drainage into a tunnel in fractured rock and numerical analysis of leakage remediation, Romeriksporten tunnel, Norway

Standard geostatistical methods for simulation of heterogeneity were applie d to the Romerik-sporten tunnel in Norway, where water was leaking through high-permeable fracture zones into the tunnel while it was under constructi on, causing drainage problems on the surface. After the tunnel was complete d, artificial infiltration of water into wells drilled from the tunnel was implemented to control the leakage. Synthetic heterogeneity was generated a t a scale sufficiently small to simulate the effects of remedial actions th at were proposed to control the leakage. The flow field depends on the vari ance of permeabilities and the covariance model used to generate the hetero geneity. Flow channeling is the most important flow mechanism if the varian ce of the permeability field is large compared to the expected value. This condition makes the tunnel leakage difficult to control. The main effects o f permeability changes due to sealing injection are simulated by a simple p erturbation of the log-normal probability density function of the permeabil ity. If now channeling is the major transport mechanism of water into the t unnel, implementation of artificial infiltration of water to control the le akage requires previous chemical-sealing injection to he successful.