Technischer Bericht NTB 84-20
Geowissenschaftliehe Grundlagen des Sondier-Standortes Oberbauen Stock
The geological and hydrogeological conditions prevailing in the region of the investigation site Oberbauen Stock have been chosen as model data-set, in the frame of project Gewähr 1985, for a type B (low and intermediate level) waste repository. The report, in its capacity as a reference report for project Gewähr presents all available, relevant site data applicable to modeling of the site.
The sources of the data are presented. Geological studies and investigations, boreholes and geophysical investigations prior to the construction of the Seelisberg tunnel (as well as all underground facilities pertaining to the said tunnel) are described.
In the section devoted to geology, the stratigraphy and the tectonics of the helvetic nappes in the area of the site are described. Further, the host rock, the neighbouring formations and the local tectonics are presented. In conclusion the geological boundary conditions of the area are summarized.
The section devoted to hydrogeology deals with the observations and measurements carried out at the surface and in the underground facilities. As well, the present state of knowledge concerning the water chemistry is described. The section also includes a description of the regional hydrogeology.
Concerning rock mechanics a summary and discussion of all available parameters and excavation classes is presented. A description of all the experiences acquired during construction follows as a second part. The section ends with a presentation of the observations and measurements of the gas content of the host rock and other formations.
A section concerning long-term behaviour concludes the report. Possible future changes of the geology and the climate are investigated. The consequences for the model site are discussed. It is concluded that a negative impact to a repository on the site is improbable on a timescale of 105 years.
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