ABSTRACT:

Geotechnical monitoring is an indispensable part of geoscientific investigation for all phases of the development of repositories in deep geological strata. In the mine of Morsleben in Germany it is applied in the already operating repository while in the salt dome of Gorleben it is performed during the phase of underground investigations in order to prove its suitability as a possible site for a repository for radioactive waste. Parallel to the geological exploration in Gorleben geotechnical investigations are executed in the shafts and in the investigation area of the exploratory mine. The investigations provide necessary site specific data and parameter for the design and development of the repository and for the long-term performance assessment. The aim and the concept of the geotechnical programme for the Gorleben exploratory mine are described. To illustrate the investigations extensometer measurements in the shafts are explained and results are presented. As an example for an effective monitoring method for an operating repository acoustic emission measurements in the Morsleben site are described and some of the results are displayed.

INTRODUCTION

Geotechnical monitoring has become a necessity for the development and licensing process of a repository for radioactive waste in deep geological strata. It has to provide data for the design, construction and operation of the repository in order to achieve and to demonstrate compliance with the required standards and regulations. Monitoring data are also necessary for use in the long-term safety assessment analysis. The purpose and the type of monitoring will change during the different phases of the development (Hugi et al., 1999). In the early phase of the development monitoring will be intensive to get profound knowledge of the site (basic conditions). It is achieved by investigations from the surface and is continued underground in an exploratory mine.

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