The Tunnel That Failed Before the Dam Was Even Full

Описание: #TarbelaDam #PakistanEngineering #MegaProjects

In July 1974, Pakistan began filling the reservoir behind Tarbela Dam for the first time. Then a tunnel inside the project gave way. Water rushed through carrying debris, and engineers had to drain the reservoir. The dam itself did not collapse, but the first filling exposed serious damage to its tunnels and nearby structures.

Why did the world's largest fill-type dam of its time suffer such a setback on its very first filling?

In this BigThings247 engineering documentary, we explore how Tarbela Dam was built on the Indus River, why its deep alluvium foundation made the design so difficult, and what went wrong with the tunnels, gates and upstream blanket during the first filling.

Discover why the documented damage went beyond a single tunnel, how the World Bank completion report describes the causes, and why no single reason can be called "the cause". We also look at how attention shifted from blame to repair, how the reservoir was refilled in June 1975, and how repairs continued for years.

We also examine the cost of the project, which rose from an estimated US$828 million to US$1.497 billion, and where Tarbela stands today, including the Tunnel 5 extension.

The visuals in this video are diagrams, illustrations and general footage created for explanation. They are not original footage of the 1974 events.

What do you think is the biggest lesson from Tarbela: foundation geology, gate and tunnel design, or testing before the first filling?

Share your thoughts in the comments and subscribe to @bigthings247 for more documentaries about the world's largest engineering projects.

Source: World Bank project completion report on Tarbela Dam.

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