2. Site reconnaissance

2.1 Geology and geomorphology

Some geological formations are renowned for their frequently unstable slopes:

• Lias black marls in Lorraine, Burgundy and Aveyron;

• Gault clays in Normandy ;

• Varved quaternary clays south of Grenoble, etc.

The first step in a slope stability study is to establish the geological structure of the site: nature of the bedrock, thickness of surface formations, presence of faults, etc. It is important that the geological study extends over a wider area than the precise location of the unstable zone. It is important that the geological study extends over a wider area than the precise location of the unstable zone....