Another dam question

Editor’s Note: A follow-up to this question and answer, prompted by the article “Geomembrane sealing systems for dams,” came from a reader in India.

Question

From: Shivani Pal
Geomembranes v/s concrete face in rock-fill dams?

Please comment, sir, whether geomembrane can completely remove the layer of concrete face required in rock-fill dams or are they an additional water retention improvers—i.e., will a concrete-faced, rock-fill dam be no longer concrete-faced if geomembranes are used (neglecting 200m-thick PCC layer)?

Regards,
Shivani Pal
Design Engineer
Himachal Pradesh Power Corp. Ltd.
Himachal Pradesh, India

Response

From: Dr. Robert Koerner

Dear Shivani Pal,

The answer to your question of eliminating a concrete covering on earth and earth/rock-fill dams when using a geomembrane as waterproofing is “yes and do indeed eliminate the concrete” provided that you can make a reasonably stable subgrade for the geomembrane.

In the 2010 International Commission on Large Dams (ICOLD) Bulletin #135, there are listed 173 such dams worldwide, with 47 upstream exposed, 106 are upstream covered, and 20 are internal. None are reported to have had a cast-in-place concrete layer beneath them.

Dr. Robert Koerner
Geosynthetic Institute and the GMA Techline

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