Field Performance of Geomembrane and GCL at Two Mine Sites

This paper describes the use of geosynthetics at two remote mine sites; one in the Andes Mountains of Chile, South America and the other in the Rocky Mountains of Colorado, United States. In Chile, a test pad was at gold mill processing facility a geomembrane was used to line the face of a tailings impoundment rock-filled dam to control seepage. A test pad was constructed at the site during construction to determine if an on-site alluvium deposit of coarse-grained soil, with cobbles up to 5 cm in size, would puncture through a geotextile cushion and into the geomembrane. In Colorado, tailings from a mill that produced lead concentrates during the mid 1900's were being capped using a Geosynthetic Clay Liner (GCL) buried under a soil layer to reduce infiltration. During the construction, the contractor proposed a method to place cover soils that would require 75-ton loaded scrapers to travel over the buried GCL on a 3H: 1V (3 horizontal and 1 vertical) slope. A full-scale test pad was constructed at this site to determine if the loaded scrapers would damage the underlying GCL. The paper describes how the test pads were constructed, what materials were used, and how they were loaded. After loading, the geosynthetics were exhumed to determine if damage occurred and if they could be used for the full-scale construction. In both test pads, the geosynthetics performed well and without evidence of significant damage. In each case, geosynthetics were used successfully to complete both mine projects.