Cavitation Damage and the Tarbela Tunnel Collapse of 1974.

Abstract

C o r r i g e n d u m Table1,24July:for'TlGlclosed'read'T1G2'closed. M r Kenn a n d M r G a r r o d The Authors believe that at the start of impounding the tunnels and gates were in good order and that all of the damage observed later can be accounted for by the subsequent Row conditions. 89. Once impounding had begun the tunnel gates and gate hoists became inaccessible. Consequently the gate positions could be estimated only to within conditions inside the tunnels. about 1 ft and there was no direct evidence of either the water levels or the Row 90. The tunnel outflow conditions and the air demand at the inlet ducts provided the indirect evidence at the time of the unknown Row conditions inside the tunnels. Piezometers were located at many places in the surrounding rock. Some of these indicated the groundwatcr pressures as these responded to both the reservoir water levels and to the break in the tunnel. Fig. 17. Cavitation damagecaused by thesheared flow of Fig. 4 Paper published: Proc. Instn Civ. Engrs, Pan 1, 1981.70. Feb., 65-89.

Cavitation and the generation of tension in liquids

“…We now turn from laboratory conditions to consider cavitation damage to concrete elements in large hydraulic structures such as hydroelectric power stations and similar installations. Two papers, one by Kenn and Garrod (1981) and the other by Kenn (1983) contain an account of the Tarbela Tunnel collapse of 1974.…”

Dams, Reservoirs and River Intakes

“…At the Tarbela dam in Pakistan in 1974 (Kenn, 1981) a thickness of over 3 m of concrete tunnel lining was eroded within about 24 hours. This is primarily to avoid cavitation; this is the formation of pockets of water vapour when pressure falls in usually fast flow to below the vapour pressure of water and their subsequent collapse which, if at a surface, can fast erode that surface (Section 13.12).…”