Abstract

The geotechnical study of the Gilboa Pumped Storage Project adopted a new in situ testing Approach which involved combining the Plate Loading Test (PLT) and a series of Flat Jack Tests (FJT) in order to determine the rock mass properties and the in-situ stress conditions. The in situ tests were used to verify the design base parameters of the rock mass, which were calculated during the preliminary design stage by reduction of intact rock properties based on the GSI method. The Gilboa Pump Storage Project (2 X 150MW) will supply 300MW of peak power to the Israel Electric Corporation (IEC). The project will include two pump-turbines that are able to convert hydraulic energy into mechanical energy and vice-versa. The project will also involve the construction of 4.5km of tunnels, two large underground caverns for the powerhouse, and a vertical shaft of 500 m depth. The geotechnical site investigation included deep core drilling to a depth of 570 meters.

The project is located in Israel and is situated 6 km west of the Jordan Rift Valley, which is an active tectonic boundary between the Arabian plate and the Sinai plate.

The rock mass properties were obtained via in-situ testing. This allowed for optimal design of the steel pipe and concrete lining along the high pressure tunnel and for the support design of the two large turbine caverns. The PLT was conducted using a hydraulic jack, which was installed in a test adit in order to measure the horizontal and vertical deformation modulus, whereas the FJT involved the installation of six flat jacks on different angles relative to the tunnel axis. The evaluation of both the values and orientation of the principle stresses will involve the development of an analytical solution for the FJT. This will occur during the next stage of the collaborative study between the Rock Mechanics research team at Ben-Gurion University and GEOTOPE Geo-engineering Monitoring Ltd.

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