An analytical method for estimating leakage from a hydraulic pressure tunnel.

An analytical method has been proposed to estimate the leakage from a water-filling tunnel between two reservoirs, based on Darcy's law and the position of the water table, for a phreatic aquifer. The variable water-fill level in the tunnel and an arbitrary intersection angle between the tunnel and horizontal plane were considered. The reliability of this method was validated by numerical analysis and the measured leakage during two water-filling tests in the Heimifeng Pumped Storage Power Station in China. The calculated leakage can represent both the measured value and numerical result due to the small differences between them. Also, the effect of some parameters on the leakage was analysed. Results indicated that leakage increased with decreasing intersection angle, the increase of hydraulic conductivity of the reinforced concrete lining, and the increase of water-fill level in the tunnel. Other parameters exerted little effect on the leakage. Furthermore, the total leakage was estimated under the simultaneous running of two tunnels. When one tunnel was running, the other tunnel was emptying. The calculated leakage was 4.48-8.85 L/s for both tunnels running, which was about 0.5 L/s less than that with one tunnel running and other tunnel emptying. This revealed that the running tunnel had little effect on the leakage from the other (emptying) tunnel. [ABSTRACT FROM AUTHOR]