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Explosive Work

November 2013

Explosions in the Christchurch residential red zone over recent months are contributing to scientific research attracting international interest.

Aerial view of the layout for a blast. Preparation for blasting starts many hours before. Concrete and sandbags are laid on top of chargers, with more than 100kg explosive material used for each blast. Darker sand patches are evidence of liquefaction (ejected sand).

Image courtesy of http://eyeinthesky.net.nz/

Tonkin & Taylor has been managing ground improvement trials for client EQC since April 2013.  A controlled blasting programme involving detonating explosive underground has been running as part of the research into how earthquake damaged land can be strengthened.

An international audience including scientists, engineers, insurers and infrastructure authorities is learning about the NZ research.  Click here for a presentation given by Tonkin & Taylor in San Francisco.

The research is investigating the effectiveness of various shallow ground improvement techniques.  Techniques include strengthening the upper soil layers with short stone columns, short timber piles and horizontal soil cement mixed beams constructed beneath existing houses.

Each ground improvement method has been tested by detonating a series of underground explosions simulating the effects of an earthquake and forcing up liquefaction from deep within the ground.  The ability of the different ground improvement methods to adequately support the foundation systems of residential houses was then assessed.

The purpose of the field trials is to find cost-effective ways to create solutions for strengthening Christchurch’s land vulnerable to the liquefaction hazard.

The research will be completed in December and several months of analysis is expected to work out effectiveness of the methods.

 

 

Auckland Unitary Plan – formal submission period opens

September 2013

A ‘one stop shop’ for planning rules in the Auckland region is on the way.

Auckland Council’s Unitary Plan will replace most of the region’s existing plans and significantly influence the future of Auckland.

The Proposed Unitary Plan has been publicly notified (on Monday 30 September 2013). Formal submissions can be made until 28 February 2014.

The way land and resources can be developed or used in the Auckland region may already have changed, as some Unitary Plan rules have legal effect from the date of public notification.

If you have any questions about how the Unitary Plan may affect current and future projects, or you would like advice on how to make a submission, please contact Peter Roan (proan@tonkin.co.nz), Andrea Brabant (abrabant@tonkin.co.nz) or Karen Baverstock(kbaverstock@tonkin.co.nz) in the Tonkin & Taylor planning team.

 

 

Abandoned mine gets a facelift

June 2013

A technically challenging project to remediate an abandoned mine site by treating heavy metal contamination has recently been completed.
Tui Mine, 2km from the Te Aroha township, was abandoned in 1975 and became one of the most contaminated sites in NZ. The underground workings, waste rock stockpiles, former processing plant and tailings dam all contributed to adverse affects on the surrounding environment.


Images of Tui Mine.

The site was operated as an underground mine from 1967 to 1973, extracting metals such as copper, lead, zinc, silver and gold.

“T&T staff have played a major role in bringing a successful conclusion to this project,” says Waikato Regional Council Chief Executive, Bob Laing.

T&T provided project technical support, peer review and ongoing technical advice that influenced the way the mine has been successfully remediated.
T&T also made a significant and influential contribution to the success of the project as Engineer to the Contract and Engineer’s Representative; so far undertaking more than 180 site inspections over the last two and a half years. These roles have included:

  • Contract management of two construction contracts totalling over $15M
  • Health and safety monitoring
  • Quality control monitoring
  • General construction supervision
  • Provision of technical advice
  • Provision of project management support.

Before the remedial work, the mine's tailings dam could have collapsed in an extreme weather event or a moderate earthquake, sending toxic waste toward the town of Te Aroha, requiring residents to be evacuated.

The tailings dam was de-constructed and re-shaped into a solid and stable landform. Another dam was constructed out of concrete within the mine and now retains up to 50m of water, flooding the lower levels of the mine.

The clean-up required more than 170,000 tonnes of contaminated material to be treated on-site. Approximately 10,000 tonnes of cement, 8000 tonnes of lime, 14,000 tonnes of rock and gravel, 10,000 tonnes of clay and 10,000 tonnes of topsoil were transported to the site.

 

 

Multiple New Year Honours Awards

May 2013

Five Tonkin & Taylor people were recognised at investiture ceremonies for people named in the 2013 New Year honours lists.
The Governor-General, Lt Gen The Rt Hon Sir Jerry Mateparae, presented insignia to four Tonkin & Taylor geotechnical engineers, and the Board Chairman at the investiture ceremonies at Government House in Wellington and Auckland in May.

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