Weep Hole Design in Water Conveyance Tunnel
Water supply mains and inland ware net-working systems require large scale of water conveyance tunnels. Recently, to control flood and measure drought, 11 km of water conveyance tunnel connecting two earth and rockfill dams was constructed in South Korea. The tunnels are generally located in the mountain areas and constructed as drains. Circular concrete liners without drainage system were installed to prevent from weathering of excavation boundaries and rockfall failure. As deep tunnels, high ground water pressure possibly act on the tunnel linings. To avoid high ground pressure and measure the lining damages, weep holes are installed, which is very costly. To reduce construction cost and efforts, design method to seek the optimal length, arrangement and interval of weep hole was investigated. A numerical parametric study on the design factors such as the number of weep holes, lateral spacing, weep hole diameter, length and longitudinal distance and arrangement are firstly performed, and theoretical evaluation is performed. Based on the analytical study and field experience, a design guidelines on the optimal method of weep hole installation is proposed.