Mining involves the design, construction, operation, and closure of many geotechnical structures, including: access roads, structural building pads & foundations, ponds, tailings facilities, heap leach pads, and waste rock dumps.
Geosynthetics are used extensively in mine geotechnical structures to enhance the performance of the soils and rocks of such structures. Geosynthetics are used to increase the strength of soil, to control seepage from mine wastes and through soils & rock, and to separate soils of different gradation and hence to limit piping and potential failure of soil structures.
The first geosynthetic that I used was the strongest grade of Bidim, a thick geotextile, to construct the starter berms of the Richards Bay, Triomph phosphogypsum tailings facility. We laid out rolls of the blanket-like material over the 30-meter deep deposit of very soft mud, joined the rolls with cut-up wire coat hangers and then let the scrapers loose to dump a meter of clean sand to form the starter berm. (See this link for the details.)
I became familiar with geomembranes when I expanded the Chloorkop gypsum dams. The geomembrane liner had a disconcerting habit of welling up in great bubble-like domes. The operators took this in their stride, telling me: “No problem; we go out in a boat to the hippos and cut a slit in them. That quickly deflates them and the black stuff sinks.” I struggled with the consequences.
As the chief engineer on the Uranium Mill Tailings Remedial Action Project, I lead the team that persuaded the U.S. Nuclear regulatory Agency to allow us to include a Geosynthetic Clay Layer (GCL) in the cover of the Estes Park tailings pile.
In Los Angeles, I conceived of an did the basic hand calculations that lead to the construction of a soil cover on the 340-ft high, steep (1.4:1.0) slopes of the Operating Industries Inc. landfill remediation project. (See this link for details.) To keep the soil on so steep a slope potentially subject to big earthquakes from the underlying faults, we brought the soil up in horizontal lifts and every five meters, laid a strong geogrid that we anchored back into the refuse. The cover is still there, although the soil tends to creep downslope and crack.
For Pond 5 of the Suncor Oil Sands mine in Alberta we proved that this cover works—it is almost constructed as I write: let the tailings freeze; place a geomembrane and geogrid layer; cover these with light-weight coke (a waste by-product of mining and oil extraction). When the tailings thaws, the coke is prevented from floating away or sinking by the geomembrane, reinforced by the geogrid. (See this link for details.)
They are still busy installing a wick drain field that we designed to dewater these tailings and hence promote its passage to a strength of 5 kPa. (See this link for details.)
Then I wrote the piece on the topic at this link. All of which leaves me with this thought: designing and building with geosynthetics is a rare challenge, a balancing act on a slippery slope; for there are few equations, little precedent, and a lot of judgement is needed. Not to mention luck.