This 11 km section of the $91 M Waikato Expressway traversed some geotechnically demanding terrain. The northern part of the route was jammed between several large block landslides, the North Island Main Trunk Railway and the Waikato River. Tonkin & Taylor was instrumental in the adoption of an innovative route option in the northern section, which bypassed the railway, excavation of the toe of the landslides and unloaded the head of many landslides, thereby significantly mitigating short and long term risk for Transit NZ and their contractors.

For more detailed information, download our pdf.

Under new Government Legislation NCC were required to assess their assets with regard to remaining asset life and current valuation. Tonkin & Taylor were contracted to put together a database of NCC’s roading retaining walls. An assessment of each walls condition, its spatial location and a risk assessment was undertaken at the same time.

For more detailed information, download our pdf.

The Blenheim Road deviation leads traffic from Blenheim Road to Moorhouse Avenue, away from the previous overbridge to Deans Avenue. A reinforced-earth embankment and overbridge were constructed to take the deviation over the existing main trunk railway line. Due to loose sand and silt in the upper 10 m of the foundation soils, significant settlement (up to 300 mm) was predicted under the overbridge abutments. Therefore a key factor driving design for this project was to ensure vertical clearance between the overbridge and railway would satisfy operational requirements for the lifetime of the structure. To mitigate this settlement risk, an extensive preloading program was developed, which generated settlement of up to 200 mm. Liquefaction was also a significant issue for the project, as the seismic vulnerability of the existing overbridge was a major reason for the deviation project. Liquefaction and settlement risk at the abutments was mitigated using vibroreplacement (gravel columns). Gravel columns were a very cost effective solution when compared to conventional piled abutment options.

For more detailed information, download our pdf.

The scheme provides for the widening of the existing State Highway 20 between Walmsley Road and Queenstown Road. 
The project involves modification and rebuilding of several existing motorway bridges, foot bridges and the construction of a duplicate bridge over the Manukau Harbour. A new interchange will also be constructed at Gloucester Park. Significant environmental design and construction constraints have dictated that a low level embankment constructed with ultra light weight polystyrene fill will be required for the new carriageways crossing the unfilled crater within the Hopua Tuff ring.

For more detailed information, download our pdf.

The 4 laning of SH 1 from the weighstation to the Paremata overbridge was a controversial project to improve the traffi c flows on SH1. The project was subject to strict resource consent and designation conditions. The construction area was adjacent to the nationally significant Taupo swamp, Porirua Harbour and Paremata Estuary. Given the public interest in the project it was essential that environmental management of construction activities ensured full compliance with the conditions. The road embankment was constructed over peat deposits. This required monitoring and interpretation of settlement and groundwater data. Advice was also provided on excavation stability within these very weak deposits.

For more detailed information, download our pdf.

The $30 M Hewletts Rd Bridge project was completed in 2006 and provides a flyover to improve traffic flows on the Mt Maunganui site of the Tauranga Harbour Bridge. Tonkin & Taylor were principal designers as part of the design build contracts undertaken by Fulton Hogan - Smithbridge joint venture. The ground conditions in the area include deep sand deposits which exhibit susceptibility to liquefaction under seismic loading.

For more detailed information, download our pdf.

The project provides a roading link between the Southern Motorway (SH1) and the new Highbrook Business Park on the Waiouru Peninsula, Auckland. The scope involves widening of SH1, including widening of the causeway and bridge across the Tamaki River, a new interchange of Highbrook Drive with SH1, a new multi-span bridge across Otara Creek and Highbrook Drive itself.

For more detailed information, download our pdf.

Tonkin & Taylor provided the structural and geotechnical engineering services for the $1.9M tramway extension project.  The 600 m long tramway extended across an old landfill and a 90 year old cast iron sewer, both of which presented significant geotechnical risk.  T&T worked with the client to provide innovative and economical solutions for the tram track, including the use of an ‘impact roller’ and a polystyrene fill embankment.  The design solutions provided MOTAT with significant cost savings over conventionally designed piled and DC options.

For more detailed information, download our pdf.

The Greenhithe section of the Upper Harbour Highway runs from Constellation Drive at the north eastern end to the Upper Harbour Bridge at the south western end. The project involves some high earth embankments (27 m) over soft ground, three interchange bridges and several MSE walls. A feature of the design is the range of special measures employed to enable construction with wet fill soils, including use of geo-grids, lime treatment and a specification to meet the design requirements.

For more detailed information, download our pdf.

Tonkin & Taylor operates three falling weight deflectometers for structural testing of pavements. A portable Geobeam Deflectometer has also been developed by T&T which provides deflection based profiling for analysis of pavement layer stiffnesses, residual life and assessment of rehabilitation options to achieve projected loading.

For more detailed information, download our pdf.

The MacKays Crossing project north of Wellington involves construction of a 4 lane rail overbridge and 2 km of realignment of SH1 at a cost of $21 M. The works include environmental mitigation measures and enhancement of the wetlands. Much of the cut is underlain by deep peat deposits and the works needed to be undertaken adjacent to live rail and a sensitive gas pipeline.

For more detailed information, download our pdf.

The Northern Gateway project involves construction
of a 7 km section of motorway between Orewa and Puhoi. The 7.5 km route crosses areas of native bush which has high environmental sensitivity and steep topography requiring a number of major bridges, tunnels and deep cut/fills. The project is currently the largest roading works in NZ valued at $350M. Special attention has been given to protection of the area and includes eco-viaducts, fish passages, water quality treatment facilities and the use of construction methods which have minimised disturbance of the bush. Tonkin & Taylor has been a full alliance member of the project design and construction team.

For more detailed information, download our pdf.

The $143 m PJK Expressway was constructed as a jointly funded toll highway project by Tauranga City and Transit NZ. At the time of construction (1999 - 2003), it was New Zealand’s largest roading project. The work involved construction of 14 km of pavement with three intersecting roads over a 20 m deep area of swamp and included a major grade separated interchange with bridge sections of up to 300 m length and piles up to 40 m deep together with a number of other bridge and retaining structures as well as deep embankments and sections.

For more detailed information, download our pdf.

The bridge was part of a controversial programme of works to improve SH 1 in the Plimmerton/ Paremata area. The project was subject to strict resource consent and designation conditions. The construction envelope was limited. Given the public interest in the project it was essential that environmental management of construction activities ensured full compliance with the conditions. An alternative ground improvement design was developed to reduce cost and environmental impacts and to allow more flexibility in construction programming.

For more detailed information, download our pdf.

The Rewa Bridge project was a design-build contract undertaken for the Government of Fiji Public Works Department which involved the construction of a 425 m long, four-lane bridge in Nausori, Fiji. The abutment and pier foundations consisted of 204 no. 610 mm diameter steel tube piles driven to depths of 50 m.

For more detailed information, download our pdf.

The Tauranga Harbour Link Stage II project involved construction of a duplicate bridge adjacent to the existing harbour crossing and an elevated expressway connecting the crossings to the existing expressway. The project includes the 470 m incrementally launched harbour bridge and the 600 m elevated viaduct. Ground conditions for the project include deep soils with significant liquefaction potential. Tonkin & Taylor has provided highly innovative cutting edge design as part of the design build team. This has included the application of numerous technologies new to New Zealand such as piling under bentonite slurry. T&T also implemented design solutions that are state of the art internationally including vertical drains and raked timber piles for liquefaction mitigation.

For more detailed information, download our pdf.