Leakage Quantity Investigation for Beheshtabad Water Transmission Tunnel by Using Analytical and Numerical Approach

Beheshtabad 65 Km tunnel is the longest pressure tunnel in Iran. Near the inlet and outlet of the tunnel due to low level of ground water، leakage of water from the tunnel would be likely. In this article at first the tunnel route in zoned and Permeability، External water head and geotechnical parameters have been studied. Analytical Fernandez''s methods is introduced and briefly discussed and Leakage quantity and water head on the lining is determined using the method. The permeability of those Chainages that are supported by precast concrete segment، determined using Darcy low and considering segment Geometry. Then flow analysis by use of FLAC software is explained. In the last part analytical and numerical results are compared to each other and it is shown that the results are very similar. However numerical methods are preferable because they have ability to consider model details such as drainage pipes، arrangement and dip of layers as well as modeling transient seepage.