WATER/WASTEWATER STRUCTURAL STRENGTHENING
In September 2014, Concrete Cloth GCCM (CC) was used to remediate a drainage ditch at the base of a slope at Pogo Mine, Alaska. The ditch is needed to prevent surface and storm water coming into contact with the adjacent mining tailings field. Due to the mine location and surrounding terrain, there are challenges with storm and surface water management.
Re-lining the ditch with shotcrete was considered, but two miles of shotcretelined ditches had been installed in the previous two years and proved this was not a long term solution. Storm water had undermined the ditch, and coupled with freeze thaw weathering and heavy spring rains, had caused extensive cracking and ultimate failure of the shotcrete.
CC allowed the installation to be completed in September when temperatures are already near freezing and there is regularly frost in the mornings - conditions which prevent the use of conventional concrete. Additionally, CC negated the costly maintenance requirements associated with other drainage solutions.
Thirty-three bulk rolls of CC5 and five bulk rolls of CC8 were delivered to the Pogo Mine site. The existing shotcrete ditch was cleaned of debris-like rock and vegetation to ensure intimate contact between the CC and incumbent shotcrete lining. An anchor trench was created at the crest of the ditch adjacent to the slope, above the level of the existing shotcrete, to prevent runoff water from the slope infiltrating under the CC. The opposite side of the ditch is located next to a road, so the bank was graded and the ditch was re-profiled using excavators.
The CC was mounted onto a small wheel loader with a spreader beam, unrolled and cut to specific profile lengths with a utility knife to avoid waste. The mine staff then laid the CC transversely, overlapping layers in the direction of water flow. The outer edges on the side adjacent to the slope were fixed with 305mm Galvanized Ardox spikes into the previously created anchor trench. The overlaps were screwed every 300mm with 20mm truss head stainless steel full thread screws. The roadside edge of the CC was then sealed with a bead of Sikaflex 1A and fixed into the existing shotcrete liner with 15mm x 10mm steel mushroom anchors. The material was hydrated via a water truck with a 50mm adjustable nozzle.
The 7225 m2 of CC was installed in 11 days at rate of up to 1000 m2 a day by a team of six in low temperatures. The install was deemed a success due to the speed of install and a huge 90 percent cost savings.
Application: Remediate shotcrete drainage ditch
Client: Sumitomo Metal Mining
Location: Pogo Mine, Alaska, USA
Installation: September 2014