Microtunneling Under Conservation Zone
The downstream section from Ch 21 to 130m crossed under a drainage reserve/tree conservation zone. This section was microtunnelled in 2 microtunnels: 50m long @ 1.04% and 59m long @1.02%. The ground was a mixture of clay and shale.
Freebore in Self-Supporting Ground
The designer specified a 500mm outer steel casing with a Ø300mm carrier. Both sections were firstly freebored as the ground was self-supporting. Despite the absence of a need for an encasing pipe, the steel casing was sliplined into the microtunnel as per the designer’s request and then followed by the carrier pipe. The annular space was grouted.
Site Setup with the Crane Truck
Setting up on the shoring at a manhole which has a change of direction.