Stone Columns – Vertical Drains
The Upper Pond Dam Remediation project was completed for VALE Nickel Mines in Sudbury, Ontario. The project consisted of the installation of Stone Columns with Wick Drains at intermediate points between the Stone Columns. The solution was designed to increase the soil strength behind the South Dam so that a large buttress could be installed.
In consideration of the poor existing ground conditions encountered at the site, it was required to carry out ground improvement in order to allow for the installation of the toe berm to increase the factor of safety of the dam and prevent potential failures.
The soils to be improved consisted of fine, machine-produced silt tailings. Prior to the start of works, the working area surface soils were excavated between two and three feet, filled with crushed stone, and roller compacted to support the heavy soil improvement equipment. The depth of improvement was about 4 to 8 m across the area.
The Wick Drains were installed prior to the Stone Columns to aid in the dispersion of the excess pore pressures and air introduced to the soil during the installation of the Stone Columns. The Stone Columns were then advanced between the Wick Drains.