Deep Soil Mixing Shear Walls
Wesdome – Kiena Mine Complex – Tailings Storage Facility (TSF)
Val d’Or, Quebec, Canada
Significant Project Features:
- Installation of deep soil mixing shear walls to improve the geotechnical properties of underlying soils within the selected dykes along the perimeter of the Tailing Storage Facility (TSF).
- Solidification of approximately 25,175 m3 of in-situ soils extending to an average depth of 12 meters below a prepared working platform.
- Average 28-day UCS result of 3.9 MPa.
Project Objective
Canada Geo-Solutions, Inc. (GSI) teamed with Menard Canada to install the Deep Soil Mixed (DSM) shear panels at the toe of select dyke locations surrounding the TSF at the Kiena Mine Complex located in Val d’Or, Quebec, Canada. The DSM shear panels were designed to improve the global stability and bring the tailings impoundment within updated regulations. The site specific design utilized information collected through an independent geotechnical investigation and improved the factor of safety against multiple failure modes (overturning, crushing, shear, etc.). The prime contract was held by Services Miniers Nord-Ouest (SMNO).
Description of Work
DSM shear panels were installed across five (5) separate dyke sections (Dyke 3, 23, 40, 41 & 42) considered to have a high probability of failure when exposed to seismic conditions as a result of the soft varved clays underlying stiff silty sands and silt. Utilizing a Manitowoc 777 equipped with GSI’s Hain Platform and a Casagrande B360, eight-foot (8’) diameter augers were advanced through the treatment zone and tied into the dense till layer residing 12 to 22 meters below the prepared platform.
Due to the use of multiple drill rigs and distance between improvements zones, GSI utilized two batch plants to produce and convey cement grout. In total, ~7,000 MT of Portland cement was used to treat and solidify site soils. Specific cement dosages were developed through a pre-construction design mix study for the various dyke segments based on performance criteria. In the end, GSI was able to achieve the designed strength and shear panel geometry required.
GSI worked through difficult drilling and environmental conditions to safely and successfully complete this project to the satisfaction of the Client.
Project Challenges
- Remote location in northern Quebec required cement to be trucked in directly from Montreal.
- Condensed schedule constraints necessitated the use of two of the largest, most powerful DSM drill rigs. GSI completed production and fully demobilized crew and equipment in the early parts of winter.
- Achieving a well-mixed soil-reagent composite in the soft clay.
