The ZEDEX (Zone of Excavation Disturbance EXperiment) project was
undertaken at SKB's underground research facility, the Äspö Hard Rock
Laboratory (HRL), Sweden, between April 1994 and July 1996. The project was
undertaken in two phases with the first experimental phase being completed in
1995 and reported by Olsson et al. (1996). A second phase was undertaken with
the experimental acquisition work performed between January and July 1996. The
results and analyses from the second phase were integrated with those from the
first phase. The result from both phases of the project are presented here.
The ZEDEX project was undertaken as a joint project by ANDRA, UK Nirex and
SKB with significant contributions from BMBF and Nagra. The objectives of the
project were to understand the mechanical behaviour of the Excavation Disturbed
Zone (EDZ) with respect to its origin, character, magnitude of property change,
extent and its dependence on excavation method. Supporting studies to increase
understanding of the hydraulic significance of the EDZ and to test equipment and
methodology for quantifying the EDZ were also performed.
The rationale for undertaking this project is that it is considered that the properties
of the disturbed zone, that develop around excavations created by the construction
of a repository, may affect the efficiency and effectiveness of plugs placed to seal
underground openings and provide enhanced hydraulic conductivities which may
negatively affect repository performance. DAMAGE AND DISTURBANCE FROM TUNNEL EXCA V ATION BY
DIFFERENT TECHNIQUES, CONCLUSIONS FROM THE ZEDEX
PROJECT