Soil investigation
Case study: Soil investigation at a storage reservoir

For the evaluation of the stability of a dam construction the condition of the foundation soil has to be investigated first. As in the present case the geotechnical situation at the edge of a former dump area is complicated a combination of appropriate investigation methods has to be chosen.

A combination of direct and indirect geotechnical methods will be considered to be the solution for this problem. A reliable statement about the foundation soil could be made using a combination of subsoil core drilling with a sufficiently large diameter and cone penetrating tests as well as heavy (and light) dynamic probing as indirect methods.

The figure of the cross-section clearly shows that the dam consists of very inhomogeneous dump material as expected before. Due to the investigations performed the construction of the foundation ground could be described in detail. To summarise, on the water side non-cohesive dump materials are dominating and on the air side mixed-grained to cohesive dump materials are mainly found. The transition from the dump area to the nature soil at the air side could be understand due to the investigations performed and due to the analysis of old documents. This result was the base for the hydraulic and stability calculations subsequently performed.

Fig. 1: Drilling cores

Fig. 2: Geological cross-section