CASE STUDY ––––––––––––––––––––––––– SH 20 to 1 MANUKAU EXTENSION edoubt Road Flyover R Manukau, AUCKLAND, NZ Reinforced Earth™ Walls TerraPlus® Precast Concrete facing OWNER: NZ Transport Agency NZTA Consultant: AECOM CONTRACTOR: Leighton Works JV Contractors Design: SKM & Golder CONSTRUCTION: 2006 to 2010 Background: The SH20 to 1 Interchange forms a The Auckland Western Ring Route three level connection between the is being implemented, in stages, to two State Highways. The uppermost provide a second major traffic route level is a ten span, curved, 240m long from the South to the North of the bridge. The bridge allows traffic from Auckland isthmus. This Route is the SH1 Southbound lanes, and from designated SH20. Redoubt Road, in the East, direct access to the SH20 west bound SH20 connects to the existing lanes. motorway passing through Auckland (SH1) at Manukau in the Reinforced Earth Ltd’s Involvement South and proceeds west and Both abutments of the Redoubt Road north to the Auckland Airport; Flyover were piled. Reinforced Earth crosses the upper reaches of the Ltd was engaged by the Contractor to Manukau Harbour between design and Supply a “Headstock Mangere and Onehunga and Restraint” system, incorporating passes through the western side of proprietary REhas galvanised steel the Auckland isthmus to connect earth reinforcing strips and concrete with the Auckland Northwest connections, for each Abutment. Motorway (SH18) at Waterview. This Headstock Restraint system The Auckland Western Ring Route controlled longitudinal displacement will, when completed, significantly of the Headstocks which allowed the reduce the traffic which now bridge designers to reduce the cross- passes through and congests the section of the piles and hence reduce Auckland CBD Interchanges. It will cost. provide much enhanced access to the Auckland Airport as well as The Redoubt Road Flyover’s western allow traffic to pass seamlessly end lands on a piled abutment though Auckland without having to surrounded by Reinforced Earth™ cross the Auckland Harbour Retaining Walls. The Contractor also Bridge. engaged Reinforced Earth Ltd to Main picture and above: TerraPlus® at the design and supply the Reinforced SH20 to 1 Redoubt Road Flyover exit The SH20to1 – Manukau Earth™ walls (TerraPlus® facing embankment. The pattern comprises three panel finishes Extension Project was tendered as panel walls) supporting both sides arranged in a chequer pattern a Design and Construct Project. and abutment wall of the western embankment. The Project was awarded to the LeightonWorks JV in June 2006. Above: The Redoubt Road Flyover western approach embankment – north facing retaining wall Features of this project: The Reinforced Earth™ retaining One unusual feature was in the walls totalled 742 sqm over a total Project specifications piling. The use of REHas to length of 150 metres. The –––––––––––––––––––––––––––– control longitudinal maximum wall height was 10.980m System TerraPlus® displacement of the headstock on the northern side of the –––––––––––––––––––––––––––– resulted in the use of multiple Abutment wall. Finish Special slender precast concrete piles. These were driven through Design of the Reinforced Earth ™ –––––––––––––––––––––––––––– voids left in the constructed retaining walls and Headstock Structure Reinforced Earth™ Reinforced Earth™ Block rather Restraint systems was carried out wall than the more usual method of in the Reinforced Earth Pty Ltd –––––––––––––––––––––––––––– first driving the piles and then Design Office in Sydney, in Area 742 sqm constructing the Reinforced accordance with the requirements –––––––––––––––––––––––––––– Earth™ Block around the piles. of the Transit New Zealand Bridge Max. Height 10.98 m Manual 2nd Edition. Independent Another, was the architectural Verification was undertaken by –––––––––––––––––––––––––––– finish. The Reinforced Earth™ Michael Adler and Associates, also Length Total length of the Structure was very visible, not of Sydney. Seismicity in this region three walls is 150 m only from both Motorways but is low resulting in the use of a also from the nearby arterial seismic design coefficient of just –––––––––––––––––––––––––––– road. 0.175g Design load Transit New Zealand Bridge Manual The Contractor achieved a nd Construction commenced in July 2 edition stunning visual impact by using 2009 and was completed to three differently coloured facing Abutment Beam level in October –––––––––––––––––––––––––––– panels arranged in a chequer 2009. The construction was finally Design life 100 years for RE walls pattern. One panel type had an completed in June 2010 after all exposed basalt aggregate with adjacent bridge works were –––––––––––––––––––––––––––– black oxide, one similar but complete ground smooth to give a “terrazzo” finish and the other painted glossy white Reinforced Earth Pty Limited Reinforced Earth Limited Level 4, 20 George Street PO Box 72 734 Hornsby NSW 2077 Australia Papakura Auckland New Zealand Ph +61 2 9910 9910 Ph +64 9 236 3385 Fax +61 2 9910 9999 Fax +64 9 236 3385 www.reco.com.au www.reco.com.au .