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 TM ) was specified. The 125m 2 CC8 TM 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 TM were deployed from a spreader beam mounted from an excavator to unroll the material across the width of the channel. Adjacent layers of CC8 TM 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, treatment 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.
Previous channel section originally lined with shotcrete and showing signs of degradation
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