The use of transmissivity data from the probe holes for predicting tunnel grouting

Abstract Results from hydraulic tests in probe boreholes in the access tunnel to the Aspro Hard Rock Laboratory, Sweden, were compared to the amount of performed pre-grouting of the tunnel made in order to reduce water inflow. It was found that the probe holes identified the major hydraulic conductors well. Also, parts of the tunnel with very tight rock could be predicted. In the intermediate range, the precision of the grouting predictions can be improved with a probe hole pattern that is better adjusted to the geometry of the conductive fractures. Data for this can be obtained by mapping of orientation and trace lengths of the water bearing fractures.