EXTENSIONS OF EXISTING HYDRO POWER PLANTS IN SWITZERLAND — HYDROGEOLOGICAL AND GEOTECHNICAL INVESTIGATIONS OF TWO PROJECTS NANT DE DRANCE AND LINTH-LIMMERN

In the framework of the extension of existing hydropower plants, Solexperts performed hydraulic and rock mechanical testing in two locations in the Swiss Alps. The projects concern the new pumped-storage hydro power stations Nant de Drance and Linth- Limmern. The results provided essential information for the design of the planned caverns and access tunnels. Investigation boreholes were drilled at both sites. Solexperts costum-made packer systems were installed to investigate the hydraulic target features after the geophysical survey of the boreholes.At the Nant de Drance site, the Solexperts double packer system was used to measure both outflow and hydraulic head below the first packer and also in the test interval. Thus, all parameters could be determined without moving the system. The results were implemented in the design of a permanently installed multi-packer system for the longterm observation of the hydraulic heads. At Linth-Limmern site, two Solexperts four-fold packer systems were used to simultaneously investigate the hydraulic parameters at different depths and to control by-passes along the boreholes. Pulse, constant-rate and constant head injection and withdrawal tests were performed which were evaluated with Solexperts software and provided reliable results to the hydraulic properties of the bedrock. In addition, dilatometer test were performed to determine the modulus of deformationand elasticity of the bedrock. Hydraulic fracturing tests served to evaluate the maximum and minimal stress directions and the tensile strength of the rock mass. Theamounts and directions of the stresses were important for the design and orientation of the underground structure with respect to dimension and type of linings of the pressure shafts

کلیدواژه ها:

Pumped-storage power station ، bedrock characterization ، hydraulic testing ، dilatometer tests ، hydraulic fracturing tests