Jack Caldwell - Mining Engineer - Robertson GeoConsultants

Today forty of us enjoyed fine presentations on geomembranes and geosynthetics for mining. Layfield, headquartered in Vancouver, arranged this seminar and the subsequent tour of their manufacturing facilities in Richmond to the south of the city.

I learnt a lot from the hour-and-more long talk by Kerry Rowe who holds the Research Chair in Geotechnical and Geoenvironmental Engineering at Queen’s University. Most of his papers are at this link. So I repeat only the few notes I made on what he said about the durability of geomembranes. He noted that the durability of a geomembrane is primarily dependent on temperature. The leachate quality, the load on the geomembrane, and whether the leachate is in contact with one or both sides of the geomembrane play a part in determining geomembrane durability.

These are not his exact numbers, but close enough to recall for those bar-room discussions on the topic:

  • At 80 degrees C, the geomembrane may not last as long as ten years.
  • At 50 degrees C, the geomembrane may last 100 years.
  • At 20 degrees C, the geomembrane could last as long as 1,000 years.

Then I made these notes on leakage through geomembranes:

  • Leakage rates are a function of the permeability of the materials adjacent to the goemembrane.
  • But the most important factors is the number and pattern of wrinkles in the geomembrane at the time the cover material is placed.
  • The warmer the weather when the cover material is placed, the more wrinkles, hence the greater the leakage rate.

The lesson learnt is to place a low permeability material (clay of GCL) beneath the geomembrane, and place a well-graded permeable material over the geomembrane early in the morning when temperatures are low and wrinkles few.

Andy Lister of Tencate gave us a spirited talk after lunch on geotextiles and geogrids. Contact him for a copy of his talk. Andrew Mills of Layfield wrapped up the seminar with a superb talk on new developments in geosynthetics. Contact him at amill@layfieldgroup.com for his presentation. An exciting eye-opener for me and an exciting promise of great things yet to come for geosynthetics in mining.