Excavation induced fractures in a plastic clay formation: Observations at the HADES URF

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Abstract

The Belgian research programme for geological disposal of radioactive waste focuses on the Boom Clay as the potential host rock formation. To examine the feasibility of constructing an underground repository in this clay layer, an underground research facility HADES has been constructed in several stages since 1980. The two galleries most recently excavated, the Connecting Gallery in 2002 and the Praclay Gallery in 2007, were constructed by means of an industrial method using a tunnelling machine. During these excavations the hydro-mechanical response of the clay was characterised. A fracture pattern was observed consistently during the excavation of both galleries. The extent of this fractured zone was determined for the Connecting Gallery, but requires some further study. A strong hydro-mechanical coupling and a clear time dependency were noticed, even at an unexpectedly large distance from the excavation. Furthermore the Boom Clay responds in an anisotropic manner to the excavation due to anisotropy in the in situ stress state and the Boom Clay characteristics. Self-sealing processes were observed and appear to occur relatively fast.

Details

Original languageEnglish
Pages (from-to)1677-1684
JournalJournal of Structural Geology
Volume32
Issue number11
DOIs
Publication statusPublished - Nov 2010
EventWorkshop on “Fault Zones: Structure, Geomechanics, and Fluid Flow” - The Geological Society, London, United Kingdom
Duration: 16 Sep 200818 Sep 2008

Keywords

  • plastic clay layer, excavation induced fractures, fracture pattern, extent fracture zone, hydraulic disturbance

ID: 372370