Construction of Pressure Tunnels

Abstract The paper focuses on two pressure tunnels in the design of “Kąty-Myscowa” water reservoir. One of them serves as a discharge conduit, whereas the other plays an energetic role. Their depths range between 0 and 75 metres and their diameters equal 5 m. Tunnels are located in the rock mass of Carpathian flysch which is anisotropic and heterogeneous, composed of layers of sandstone and clay shales and intersected with interbedding fissures and numerous joints. The paper is divided in two parts. The first part focuses on methods of excavating and supporting, as well as injecting and sealing (i.e. waterproofing) the tunnel. In the second part, a numerical analysis using the FLAC2D code based on the finite difference method was carried for calculating displacements and internal forces in the preliminary support and in permanent lining. Results of the analysis allow for the assessment of conditions in the tunnel during its excavation and exploitation stages.