Comparison between blasting and wire sawing regarding hydraulic properties of the excavated damaged zone in a Tunnel – Experiences from crystalline rock at the Äspö hard rock laboratory, Sweden

Paper in proceeding, 2018

In tunneling with blasting, the tunnel periphery could be damaged (the EDZ, "Excavated Damaged Zone") with altered mechanical, hydraulic properties and reoriented stresses. In recent underground infrastructure projects, diamond wire cutting is used as an alternative excavation method. At the Äspö Hard Rock Laboratory in Sweden investigations have been conducted to determine hydraulic properties of the EDZ at water saturated conditions. Comprehensive hydraulic testing (hundreds of injection tests), in the floor of a blasted as well as a wire sawn tunnel section has made it possible to quantitatively compare hydraulic properties of the different excavation methods. Diamond wire cutting, as expected, greatly reduces the EDZ permeability compared to blasting.