SKETCH NO. 8

Top down construction to create a tunnel like structure

Approximately one half of the road is closed to traffic and the remaining half is used for running one lane of traffic. Secant piles are constructed along the edge and then the road is dug up down to the approximate soffit of the deck to be constructed. The ground is then leveled to the actual soffit level, steel reinforcements are then placed. Concrete is poured to a width required to run a lane of traffic on top. Concrete when cured is waterproofed and surfacing laid ready to run traffic switched from the other half. The same process is then followed to complete the road deck and surfacing. The ground is then dug out from beneath from the tunnel portal ends to create the void. Finally a concrete deck is cast at the base of the 'tunnel' and road surfacing laid to complete the job. In Guildford, Quarry Street could be used for southbound traffic and in Onslow Street, the diversion could be placed on the new East West link. 

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