ABSTRACT:

After a presentation of the excavation method and of the support concept implemented in the ANDRA underground research laboratory, at Bure (France), the authors explain the various geotechnical phenomena observed during the laboratory extension (2007–2009).The efficiency of the different support elements – at the front and at the faces – is then analyzed in regards to the different digging configurations: direction of the gallery in relation to the main major stress, dimension of the excavation, localized modifications of the support, position of the phenomena around the gallery, etc.

1 INTRODUCTION
1.1 The ANDRA underground research laboratory

The Meuse Haute Marne Center Underground Research Laboratory, located in the small town of Bure in the Meuse district (France), is a site one of a kind. In the 500 meters of already excavated galleries at −4490m deep, the scientists of ANDRA (French national radioactive waste management agency) have conducted a series of experimentations in order to study the feasibility of the A and B type radioactive wastes (high/intermediate-activity level and long life) storage in an argillaceous rock formation (Delay and al 2007). These researches have allowed to study the properties of confinement of the Callovo-Oxfordian clay formation (at a depth between 420mand 550 m) and to demonstrate the feasibility of a repository for radioactive wastes in an argillaceous rock formation (Andra 2005). Since 2006 Andra has launched a new program of tests and demonstrations. So new experimentations will be carried out in order to increase and confirm preceding results, they are no more focalized on the confinement properties. The experimental concepts are becoming closer and closer to the repository concepts in order to demonstrate their feasibility in situ. In this frame the network of galleries has to be extended to enable to carry out new experimentations.

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