Out of print publication, available as a photocopy only

Description: This report deals with the hydraulic design of full-flow tunnels driven through hard rock by conventional blasting techniques which are either completely unlined or have a continuous concrete slab laid in the invert.

The objects of the report are two-fold:

1. To present world-wide data on the hydraulic performance of unlined and lined-invert rock tunnels flowing full and to draw conclusions about the effects of the concrete invert on their hydraulic resistance
2. To formulate recommendations for the design of unlined and lined-invert rock tunnels.

The research included special field tests on a lined-invert rock tunnel in Malaysia. These new results provided an essential part of the data, analysis of which showed that the actual hydraulic resistance of lined-invert tunnels is substantially less than existing theory predicts.

The costs of some typical tunnels are calculated using the design method proposed. Numerical examples show that economies of up to 14% can be achieved by using the new data for lined-invert tunnels.

Thus the necessity of lining the invert of a power tunnel in order to prevent rock fines passing though the turbines and to improve vehicular access can be turned to considerable advantage and the cross-section and cost of the tunnel both reduced.