Our innovative design comprised the development of large 2.4 m by 2.4 m by 0.35 m thick precast concrete panels which are recessed into the slope and tied to the anchors to restrain the landslide movement.

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Highlights have included being involved with the first of a new generation of wind farms constructed in New Zealand where turbines in excess of 1 MW were used and conducting the geotechnical investigations for the largest wind farm in the Southern Hemisphere.

Our contribution

• Geotechnical assessment and recommendations on foundation design, landslip and seismic hazard including design of tie-down foundation systems to deal with difficult and variable conditions
• Analysis of foundation deformation
• Construction inspections and advice
• Preparation of resource consents
• Preparation of environmental management plans and site environmental plans
• Geotechnical and civil advice, investigations and foundation design
• Advice on re-vegetation
• Civil and Geotechnical Feasibility assessments.

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It was one of New Zealand’s largest and most challenging roading construction projects. The total earthworks reached over 4,000,000m3. Our contribution involved the first known application in New Zealand of pre-cast segmental box girder construction, using a self-launching overhead gantry for erecting pre-cast segments by a balanced cantilever method.

T&T were part of the geotechnical design team on the project that was multi-faceted, involving tunnels, bridges of unique design, major culverts and substantial earthworks. Best-practice environmental engineering methods were used to protect sensitive environmental areas both during construction and on an ongoing basis. A unique solution to protect the valuable ecological corridor around the Otanerua Stream involved the design and construction, under extremely tight environmental controls, of a 265m long Eco-Viaduct (25m wide with a clearance of 32m over the stream and eight spans of 32m). The alignment chosen allows heavy vehicles to maintain a much greater speed, reducing the differential speed to light vehicles, with benefits for road safety. Travel times are shortened and traffic congestion on the Highway is reduced.

We picked up a number of engineering awards for our work on the Northern Gateway.

Our contribution

• Geotechnical investigations design and supervision
• Engineering geology for the twin 370 m length tunnels and engineering design of the tunnel portals
• Bridge foundations for structures up to 600 m long and 30 m high, and retaining wall design
• Environmental planning and resource consents
• Hydrology and drainage design
• Earthworks design, sediment control and viaduct systems
• Embankment design for fills up to 20 m
• Cut slope stability for batters extending up to 50 m deep
• Pavement design

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See if you can spot Robert Hillier, our geotechnical group manager, speaking about the project.

We are one of the key alliance members overseeing the design, construction and implementation of the project, whilst maintaining traffic flows of up to 160,000 vehicles per day over the viaduct, managing the busy Broadway thoroughfare and keeping the existing commuter link rail line all flowing. Our innovative approach has allowed for improved motorway capacity midway through the replacement project, and keeping traffic moving in both directions throughout. The highly complex methodology we have implemented will see construction taking place immediately next to the live motorway.

We have been at the centre of the design for the new viaduct, which sees it being constructed by pre-cast match-cast segmental balanced cantilever methodology – where the bridge decks are built out equally either side of the columns until they meet in the middle. At the heart of the project is a 150m long 700 tonne horizontal gantry crane, affectionately referred to as the ‘big blue’.

While they may look identical, each of the new viaduct’s 468 bridge segments is unique, designed for its specific position. The segments, which weigh approximately 80 tonnes are created at the project’s pre-cast yard at East Tamaki and transported to the site. To cater for the temporary imbalances through this construction process, ‘out of balance supports’ – comprising over 90 tonnes of steel and concrete – are installed around each column.

We have used the learning from our involvement in another nationally significant roading project, the Northern Gateway, and applied it to the Newmarket viaduct connection.

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The site is located in an area of high siltation with marked variations in hydraulics either side of the causeway, which posed numerous geotechnical challenges that our experts overcame. Due to the scale and works, we carried out detailed assessment of the physical effects of the Johor Straits and contributory rivers.

Our contribution

• Geotechnical investigations
• Environmental planning
• Hydrology and drainage design
• Earthworks design and sediment control
• Supervision of dynamic compaction operations, instrumentation and monitoring of works.

We have analysed many different civil engineering and mining problems, such as deep basement excavations for multi storey buildings through these tools. 

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FLAC3D 4.0 Feature Tour Parts 1-4

Numerical analysis allows many factors including construction techniques, geology and groundwater flow to be incorporated into a single analysis. We have found this to be particularly important in high density urban areas where construction effects on neighbouring properties and infrastructure are important.

We commonly use these tools in opencast mine projects with complex structural geology. Numerical analysis helps us to assess the stability of excavations and provide predictions of deformation to benchmark survey monitoring against.

Other examples include, large dams that need to be assessed for performance during earthquake events and retention systems and tunnelling works for transportation projects.

Triggered by a band of intense rain, the debris-flows destroyed or damaged some 100 homes and deposited an estimated 350,000m³ of debris within the environs of the town.

T&T undertook the detailed morphological and hydrological assessment of the Matata debris flow event. We analysed options for the mitigation of future flood and debris flow events, which involved detailed design of works including culvert upgrades, debris diversion bunds, erosion protection works, and debris containment works. This debris-flow control system, which is in the final stages of detailed design, will be the most extensive ever to be designed or constructed in New Zealand. Its central component is the world’s largest flexible “ring net” barrier.

We used RAMMS, an innovative numerical code, to undertake extensive simulations of the 2005 debris flow event as well as to evaluate a range of possible control systems with respect to performance (risk reduction), physical impact, cost and land acquisition requirements.

The playground is the amazing geology and geomorphology of New Zealand and the dynamics of active plate tectonics. It’s about the varied and interesting work that abounds and the fun we seem to have doing that work. I have to pinch myself regularly about how fortunate we are doing the work we get to do.

Tell us about your time at Tonkin & Taylor thus far, when did you join and why?

I joined T&T 15 years ago with the intention of working for one year and then doing the big OE! I have now been here 15 years! (which has included a two year stint in the UK). I have been on a great journey at T&T with some great people. The work has been nothing short of fascinating and varied.

Describe your role?

I am a senior Geotechnical Engineer specialising in natural hazards work together with temporary retention and ground improvement design. I am a team leader and project Director. I get to work in the specialist areas that inspire me with a great bunch of people that I respect hugely for their technical skill and friendship.

How has your career developed here and how have you been supported?

The philosophy at T&T is to provide staff with projects that will extend and challenge you. You are expected to take ownership and manage projects early in your career. This is balanced with a wealth of senior staff support to mentor and coach development. I arrived at T&T a fresh snotty nosed pimped faced graduate but within six months was managing small projects and within two years large projects. The support, guidance and knowledge imparted by the senior staff has been fantastic and has propelled my personnel development well beyond a place I thought I would go.

What do you like about T&T?

T&T is all about doing the type of work we enjoy and helping people at the same time. It is about working in a balanced way. The philosophy is to work hard while at work but to maintain and foster interests and a life outside work. I see it as a big extended family that comes together to help and support each other while giving in a very real way to the community.

If you are interested in joining us please apply now

I work as a designer and project manager within the geotechnical group. I spend the majority of my time assessing slope instability, designing retaining walls and ground remediation, providing natural disaster assessments for the Earthquake Commission and working on the geotechnical aspects of large scale projects such as landfill development and dams.

Tell us about your time at Tonkin & Taylor thus far, when did you join and why?

I joined Tonkin & Taylor in March 2009 after deciding to move back to NZ after working in Vancouver for a few years. But I first heard about T&T’s reputation a couple of years earlier while working for another consulting company within NZ. T&T was described to me as a great company to work for in terms of training and work variety so I decided to apply before I moved back.

How has your career developed here and how have you been supported?

Both the formal and on-the-job training that is provided by our technical experts has greatly increased my technical skills and knowledge. I have been encouraged to formulate and pursue career goals through a career development program. Our projects are varied enough that I am able to choose what I work on to achieve my goals.

What do you like about T&T?

My favourite aspects about T&T are the people I work with and the culture that we foster in the group. I also like the option to work between disciplines. For example, I sometimes work on design teams for projects run out of the Waste Management Group or Water Group. By working cross-discipline, I am able to expand my contacts within the company and gain exposure to different types of projects.

What does the geotechnical playground mean to you?

At T&T I’ve had the opportunity to work with really interesting and active geology. While on job sites, I’ve observed the result of landslides, rock fall, inundation and liquefaction. I have seen, in person, earthquake damage to retaining structures, foundations, buildings and other infrastructure. Ground conditions and geology in New Zealand can often be variable, and at times complex, making design work more challenging and interesting.

If you are interested in joining us please apply now

I joined T&T in December 2005 as a summer intern at the Northern Gateway Alliance. I worked part time in T&T throughout my university study. I graduated from University of Auckland with a BE and joined T&T as a graduate civil engineer in 2008.

During my internship period with T&T, I was given the opportunity to get involved in a number of geotechnical engineering projects. I found the projects very interesting and full of challenges.

This experience encouraged me to find out and learn more about geotechnical engineering. By joining T&T, who are known as one of the leading geotechnical engineering consultants in the country, I have been able to pursue my desire to gain more knowledge in geotechnical engineering. People in T&T are helpful and supportive which I believe is important for my development.

Describe your role?

I am a Geotechnical Engineer. I provide support and input mainly in geotechnical engineering ranging from scoping and supervision of site investigations, geotechnical analysis and design such as slope stability analyses, wall and embankment designs, to reporting and project management.

How has your career developed here and how have you been supported?

T&T have played a significant role in my career development. I have been given the opportunity to get involved in various challenging and interesting projects. All senior staffs are approachable and helpful. They are willing to spare time in their busy schedule to support me and give me guidance when needed.

We also have annual development discussion with a senior staff which gives me the opportunity to express what I need for my career development and also what has worked well and what has not worked well throughout my career. It is an opportunity for the senior staffs to convey some constructive and motivational feedback on my work.

T&T also have comprehensive training programmes which help staff to develop and polish their technical and non-technical skills.

What do you like about T&T?

I like the people at T&T. People who are supportive and helpful and also passionate about the work they are doing in order to achieve the best results for us, our clients and community.

I also like the ‘flat structure’ that T&T has. It gives me the opportunity to get involved in almost all aspects of projects which provides significant help to my career development.

What does the geotechnical playground mean to you?

To me geotechnical playground means numerous and various geotechnical engineering projects both domestic and international. It ranges from a small retaining wall failure inspection in a residential property for insurance claim to large multimillion infrastructure projects such as landfill development, dam construction, bridges and tunnels. It comprises active and complex geology, geotechnical problem solving, design and innovation, and construction.

If you are interested in joining us please apply now