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Industry
Civil Infrastructure
Challenge:
A durable and fast-installing solution was needed in August 2016 to reline and realign a large diversion channel at a remote underground mine on Central Vancouver Island, capable of handling steep slopes, high water velocities, and uneven terrain without the logistical burden of shotcrete.
Achievement:
The installation was completed in just six weeks with a small crew and minimal specialist training, allowing the project to finish ahead of heavy rainfall and avoiding costly delays at the remote mine site.
Product Used:
Concrete Canvas®
Location: Central Vancouver Island, Canada
Project Type: Product Supply
Product Used: Concrete Canvas® CC8™ Bulk Rolls
Project Context
In August 2016, over 11,000m² Concrete Canvas® (CC) GCCM* was installed as a protective liner for a large diversion channel at an underground zinc and copper mine on Central Vancouver Island, Canada.
The diversion channel, which conveys clean water from the hillside above to a lower creek, was originally lined with shotcrete but the material had begun to degrade over time. It was recommended that the diversion channel should be enlarged and realigned
to effectively handle the high-water volume and velocities.
Alternative options such as replacement shotcrete were considered, however Concrete Canvas® was specified due to its ability to cope with high water velocities, its ability to accommodate variance in profile and the ease of repair if future damage occurred due
to falling trees or large boulders from the above hillside. Since the water was diverted away from the channel during installation, the speed of installation was key as the diversion pipes wouldn’t be able to handle the high-water volume expected to begin in
early October. The use of CC meant measures could be in place much faster than using conventional concrete or shotcrete. The fibre reinforcement inherent in CC gives a durability and design life well above competitor geomembrane products, whilst the
integral PVC backing ensures minimal water loss in the diversion channel.
The channel was designed to handle water velocities of up to 20m/s with slopes as steep as 16% and 20% in some sections.
Installation
Prior to excavating the new diversion channel, the main contractor completely removed and disposed of all trees, brush and other vegetation growth in the area. Any standing water was drained away from the exposed excavated areas to prevent pooling
and infiltration.
Prior to installation, a new channel was created which was significantly wider than the original shotcrete lined channel. The final channel measured 735m in length, 5-8.5m wide with an average depth of 1.5m with a 2:1 side slope. Due to the anticipated flow
velocities, 8mm thick Concrete Canvas (CC8™) was specified. The 125m² CC8™ bulk rolls were delivered to site and positioned strategically along the channel to save time and minimise handling and vehicle movement during installation. 
To account for the variation in profile width, a transverse layup was specified and bulk rolls of CC8™ were deployed from a spreader beam mounted from an excavator to unroll the material across the width of the channel. Adjacent layers of CC8™ were overlapped by 100mm in the direction of water flow and secured using 1.5m earth percussion anchors with 3mm stainless steel cables every meter along the overlaps in conjunction with 8 stainless steel 1” screws at 150mm intervals. The Canvas was pinned into 300mm deep anchor trenches on either side of the channel using the 1.5m earth percussion anchors. The trenches were then backfilled with material to provide a neat termination and to prevent water ingress underneath. When fixing the Canvas to rock in some sections of the channel, Hilti rock anchors and 600mm rock bolts were used.
The material was hydrated using a water truck and due to CC having a very low wash out rate and low alkaline reserve, trea™ent of the run off from installation was not required. CC has a working time of approximately two hours from hydration, meaning that work can continue even in very wet conditions. This can reduce programme disruption typically caused by bad weather when using traditional solutions.
Concrete Canvas® (CC) is a Geosynthetic Cementitious Composite Mat (GCCM), a factory-produced material combining cement within geosynthetic layers that hardens when hydrated for erosion control and weed suppression.
Summary
The installation took 6 weeks to complete with an average crew size of 6 men and daily temperatures up to 34°C. The client was satisfied with the product and the minimal amount of specialist training or equipment required. In addition to this, the speed of installation meant the project was completed before the heavier precipitation arrived at the mine in early October which may have caused significant project delays.
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