ABSTRACT
The paper describes the complex site logistic and the challenging underground operations for the realization of the 14.7 km long tunnel excavated by the EPB TBM and the 4.3 km of micro tunnels executed by two Pipejacking MTBM. The tunnels are only a part of the Central Interceptor of Auckland, an extended infrastructure that will constitute the largest wastewater project in New Zealand, for stormwater and wastewater control, avoiding the 80% wastewater overflowing in any weather condition. The tunnels are being excavated in geological formations constituted by Kaawa Formation, Tauranga, East Coast Bays Formation (ECBF), Parnell Volcaniclastic Con-glomerate (PVC) and Basalt (with a water pressure up to 3.5 bar). A 1.5 km stretch of the TBM Tunnel will be excavated under Manukau Harbour at a depth of 35 m. One bilobular Shaft constructed with diaphragm walls was built for the launching of the TBM. Additional sixteen circular shafts, excavated with various mining methods, will be crossed by TBM and Micro TBM tunnels. The paper will illustrate the site installation for optimising the tunnelling operation, the selection and configuration of the TBMs in compliance with strict technical specifications, new methodologies for the launching of the TBM and supporting the TBM along the tunnel construction. Special consideration has been given to the treatment and reuse of the extracted material, minimising the environmental impact of the project. All the works have to be carried out with consideration for community and stakeholders in the populated area of the city of Auckland.
