[PROJECTS]
The Wave 4 section of the Pacific Highway Upgrade between Woolgoolga to Ballina (W2B) is just north of Grafton in an area known as Tuckombil Canal, and traverses areas having significant depths of soft soils.
These early works were undertaken to ensure appropriate management, pre-load, and settlement of soft soil areas prior to major roadworks commencing on this section of the highway.
High-strength geosynthetic reinforcement.
Foundations for the Wave 4 project consisted of 600-millimetre drainage rock (including wick and bridging rock), followed by the installation of wick drains and geotechnical instrumentation to monitor soil conditions.
Around 330,000 cubic metres of earth fill was placed as the surcharge material within high strength geosynthetic reinforcement interwoven at specific locations and levels to prevents slips or embankment failures. Geotechnical monitoring equipment installed and subsequently managed, including 90 settlement plates, 12 vibrating wire piezometers, 10 standpipe piezometers, 21 inclinometers, 6 hydro-static profile gauges and 5 magnetic extensometers.
Due to the significant sensitivities of the projects work area, as well as the significant water management required, erosion and sediment control was vitally important.
The project team used industry best practice controls including the placement of the top-class soil binder, Vital Bon-Matt HR instead of bitumen emulsion adjacent to highly sensitive creeks and drains in threatened fish habitats.
Due to the final design gradient of an abutment, soil binders were considered inefficient in stabilising the batters nearby to an OPP waterway.
The project team devised a system of installing geofabric and pinning it to the batter using takes to ensure the batter could be stabilised without impacts on the fish habitat below. Based on its success, this system was used on six batters throughout the project.
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