Geosynthetics August/September 2022 - 19

Construction considerations
for wick drain ground
improvements
In the first of two parts, the authors explore the background
of construction of a large mine waste stockpile at the Rainy
River Mine in Ontario, Canada.
By Michael Etezad, Ben Riddell, Ken Bocking, Dennis Becker, Travis Pastachak,
Jason Bell, Erik Wimmelbacher and Steve Boileau
C
onstruction of a large mine waste stockpile was required at the Rainy
River Mine in Ontario, Canada. The mine rock stockpile foundation
has up to 131 feet (40 m) thick of low to high plastic, slickensided and lightly
overconsolidated clay deposits. The stockpile required foundation ground
improvement to support the planned ultimate height of more than 131
feet (40 m), to be raised over six years. Prefabricated vertical drains (wick
drains) are used to accelerate the dissipation of excess pore water pressure
due to stockpile loading, resulting in an increased rate of strength gain in the
foundation clay. About 8,530,183 linear feet (2,600,000 linear meters) of wick
drains over the area of 8,309,738 square feet (772,000 m2) were installed over
the course of two field campaigns in 2019 and 2020. Wick drains were installed
beneath the stockpile perimeter slopes and crest, over a width varying
from 453 to 661 feet (138 to 203 m). The outer boundary of the wick drain
ground improvement area was maintained at 89 feet (27 m) inside the toe
of the stockpile. Overburden waste is placed at the interior of the stockpile
and rockfill is placed at the exterior, buttressing the interior overburden fill.
Only rockfill is placed above the wick drain zones.
Foundation conditions
The soil stratigraphy generally consists of (in order from ground surface
to bedrock):
* A thin organic surficial layer
* Upper glaciolacustrine deposit
* Clay till
* Lower glaciolacustrine deposit
* Granular till
* Bedrock
PROJECT HIGHLIGHTS
RAINY RIVER MINE
OWNER
New Gold Inc.
LOCATION
Ontario, Canada
ENGINEERS
WSP Golder
GEOTEXTILE PRODUCTS
Titan TE-BXC30 biaxial geogrid
composite; TenCate Mirafi HP370
reinforced woven geotextile
WICK DRAINS
Mebra-Drain MD-88
Michael Etezad, P.Eng., is a principal geotechnical
engineer at WSP Golder in Mississauga, Ont., Canada.
Ben Riddell, P.Eng., is a lead geotechnical engineer
at WSP Golder in Mississauga, Ont., Canada.
Ken Bocking, P.Eng., is a fellow geotechnical engineer
at WSP Golder in Mississauga, Ont., Canada.
Dennis Becker, P.Eng., is a fellow geotechnical engineer
at WSP Golder in Mississauga, Ont., Canada.
Travis Pastachak, PMP, is capital projects manager
at New Gold Rainy River Mine.
Jason Bell is projects technical supervisor at
New Gold Rainy River Mine.
Erik Wimmelbacher, P.Eng., was project coordinator
at New Gold Rainy River Mine for the work and is
now underground engineer.
Steve Boileau, P.Eng., P.Geo., is geotechnical
engineer at New Gold Rainy River Mine.
All figures courtesy of the authors.
GeosyntheticsMagazine.com
19
http://www.GeosyntheticsMagazine.com
Geosynthetics August/September 2022

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