This contract was to construct an in-ground, reinforced concrete palisade wall. There had been a large slip over 2 properties which was undermining a swimming pool and house on one property and preventing works to demolish & rebuild on the other. The steep coastal environment also had a public walkway/footpath at the bottom of the 30m cliff. The project involved the installation of 23 number, 8.0m deep 600mm diameter reinforced concrete piles and 5 number, 12.0m deep 1200mm diameter reinforced concrete piles.
Working on top of the 30m high cliff definitely presented some challenges. We had to ensure the bank was safe to work from using our piling equipment. In consultation with the engineer we were able to develop a methodology where we commenced works from the end of the wall that had the most stable bank and ensure that all works further out onto the bank were completed with the piling equipment working from behind the already installed piles. This meant that additional temporary works were not required, thus providing value to the client. We had very limited access for large machinery so we constructed a temporary access platform in order to be able to get the mobile crane on site so that we could lift the (up to) 4T reinforcing cages into place.
The ground conditions of the first 5 meters of the drilling was challenging as had a tendency to collapse. Temporary casings were used for the 600 mm diameter piles and permanent casings for the 1200mm diameter piles to overcome this.
We devised a method of progressively retaining the slip so that we could use the retaining wall as a drilling platform as we worked our way along the cliff face. This ensured that our machines were always working from a stable & secure spot, ensuring safety of our machine and operators. This also ensured that there was not the cost of additional temporary works to the client.