The grouting subcontract award by Tideway to Subcon created around 20 local jobs and involved setting custom designed grout packers in the microtunnel annulus to seal against tidal movement and support the grout plug.
The packer train was remotely set ~70m into the tunnel, submerged just below the lowest tide mark in zero visibility conditions. A 120m3 Ultra High Performance Grout Plug was then set on top of this packer, thus securing the export trunkline against corrosion in the intertidal zone.
Horizontal grout plug installations using high performance concretes are technically challenging with Subcon facing high ambient temperatures, long distance pumping of over 100m through a large exothermic grout mass combining to accelerate set times and reduce pumpability. To meet these challenges Subcon provided its unique super pan mixer spread including twin auger fed, 1m3 planetary mixers, a refrigeration plant, twin 70bar piston pumps and a computerised batch loading and monitoring system.
Subcon’s unique combination of high capacity grouting equipment, engineering, QHSE culture and professional grouting crews meant the job was completed safely and on schedule.