ACEGrid® for Tailings Dam Capping

The Project

Senescent mine tailings ponds and dams consist of a partially dewatered slurry that has little or no load-bearing capacity. These geotechnical properties present a challenge for design engineers in the rehabilitation process. The challenges In a recent project, the mine site required a working platform of suitable strength to support earthmoving equipment distributing backfill over the area.

With undrained shear strengths of less than 15kPa, a substantial increase in the load capacity was required.

Our Solution

The preferred solution was to adopt a nonwoven geotextile and a high-strength geogrid multi-layer.

The reason for this approach was simple. The nonwoven ProFab® geotextile layer provides a separation layer to minimise the pumping of fines and the heaving of the foundation material. Additionally, the ACEgrid® high-strength geogrid provides a reinforcing layer to increase the tensile capacity of the tailings material and thereby its load-carrying capacity.

ACEgrid® high-strength geogrids can also be fixed together so that the required overlap is maintained. A structural join was not used in this case. Tensile strengths up to 1000 kN/m are available in the ACEgrid® range. Plus, the high tenacity polyester yarns provide long-term creep resistance and superior long-term design strength.

ProFab® nonwoven geotextiles are available in up to 6m wide rolls providing faster installation times and less overlap wastage. Coupled with the wide ACEgrid® rolls, this composite solution enabled the mine site to construct a fast, practical and economical solution for the capping layer.

Reclamation of mine tailings using geosynthetics will enable the reuse of this land in a shorter time than would otherwise be required, which is a favourable outcome for the environment and for local communities.