Fracture Aperture Measurement and Consequences for Grouting

Paper in proceeding, 2013

The hydraulic and the mechanical apertures of fractures and the relation between them are of interest for hydromechanical (HM) coupling and design of grouting works and reinforcement. The fracture geometry will influence water inflow to underground constructions, penetrability and penetration length of grout and mechanical properties of the fracture. This paper aims at presenting fracture geometry measurements on one fracture sample and to use this as a basis for a discussion on consequences for grouting. To measure surface topography of the two sides of a rock core fracture sample from the TASS-tunnel, Äspö HRL (Sample and sampling described in Ericsson et al. 2009) commercial equipment for stereo photogrammetry was used. Prior to scanning each surface, their relative positions were determined at 1.0 MPa confining pressure. The procedure enables a computer comparison between the surfaces, rendering an aperture map for the specific confining pressure. The measured surface geometry provided a data set that was put in the context of hydraulics, mechanics and hydromechanics. Comments on how the applications inflow, grout spread, fracture deformation and block stability can be related to the fracture geometry are given.