Microtunnels to connect High Voltage switch rooms
During the design phase the Leighton Contractors and Baulderstone Hornibrook Bilfinger Berger Joint Venture (LBBJV) realised that a series of microtunnels in the congested confines of tunnels would require equipment which had the strength to cut through the hard rock yet be versatile enough to be able to gain access to the site without interfering with the construction of the main tunnel.
After consulting with Pezzimenti, the various cross-passages linking the 2 main tunnels were designed to accommodate Pezzimenti equipment. Microtunnels linking the cross-passages were required for the high voltage supply for the operating tunnel.
Radial Bores microtunnelled at low points
Clem 7 has 2 low points and at each low point storm water is collectedand pumped from the tunnel. At each low point a series of radial bores from a single shaft were drilled in order to collect the stormwater from the main tunnels. Flanged Ductile Iron pipes were then inserted into the bores.
The modular hydraulic power pack being craned for transport into the tunnel
The craneage setup for the microtunnels to link adjacent passages
Jacking frame sitting on top of support frame
Microtunnelling the higher level bore to the next cross passage
The yellow tunnel lining had to be removed to enable microtunnelling to be received.
Setup of the crane truck within Clem 7
Microtunnelling the radial drainage lines in the low point sump
Completion of one the radial bores can be seen to the right of the jacking frame
Very hard quartz rich igneous rock was encountered. Location of a rock bolt now removed can be seen at 1 oclock on the bore
Close up of the ground and drilling rods.