Dynamic rockfall protection

Elite GTS logoWe wish to present here the very efficient rock fall solution by the Company Elite, with whom we are in close contact. We have been working for them 15 years ago on one of their trial test and we regularly meet their sale representative, in NZ and in France recently.

They have specialized for 20 years on designing, conceiving, installing and testing rock fall barriers and screens in parallel with any other rock stabilization works. We suggest you have a look on their site www.elitegts.com, especially on their Elite 5,000kJ product.

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These products are more specialized than any other worldwide renowned barriers retailers for the following reasons:

  • lighter,
  • requiring less anchors,
  • with their own patented retaining mesh easy to install,
  • the net positioned above poles, though preventing them to be hit,
  • posts are not anchored: the post can be installed where needs to be, the best rock can be used to anchor cables as these can be extended
  • all absorption capacity relies on dissipators to dynamize the potential impact. Active rock catch is the key, as in rope access safety in general.

The Elite system is made up to be installed by abseil drilling means, closer to the potential instability, reducing cinematic and uncertainty on blocks travel.

Not exactly the same approach as those steel retailers who try to sell you bigger barriers built down the slope, close to the highways and involving lots of anchoring…

With kilometers already installed in Europe, this product has made its way.  There is surely a scope for them on the Milford and the West Coast roads. We are ready  to import and install them (only mesh, brakes and patent need to be brought in; the rest can all be done here: posts, cables and anchor systems).

Yearly safety improvement on SH6 for NZTA – Nevis Bluff near Queenstown

 In association with Downer Edi Works and Opus International, we have scaled and blasted 2 rock features from the  230m high face: Epsilon VI and the Lower West Column for a total amount of 35 cubic meters.
These features that are regularly monitored by Opus, were highly fractured and threatened the road and traffic below.

Epsilon VI direct access on rigging
    
Setting up one of the three blast wirings at Epsilon VI.                          Click to enlarge

After the rock removal, we have drilled, installed, grouted and tested 10 rocks bolts (between 4.5 and 9 meters deep) at 100 meters high  on the West column. 

Also for reinforcement purpose, we then carried out a complete installation of a mesh on the Lower West Column, in a very overhanging zone. The location of anchors is carefully chosen to make sure the mesh fits well.

Click to enlarge

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We want to thank the road users for their patience that allowed the State Highway 6 to be safer between Cromwell and Queenstown.

Second mesh at Frances Hodgkins!

Access: Even with a fragile barrier at the top of the slope, we are still able to find a way to rig safely.

Drillability: The presence of clay at different depths has obliged us to alternate the use of a down hole hammer and drag bits, to drill top anchors 4m deep embedded in 90mm holes, whereas on most jobs of that kind just a hand-drill and 2m holes should do.

Nevis Bluff: successful and in due time!

Access and safety 

Climbing up to the workplace,credit J Barbour (c) DAS
Climbing up to the workplace, credit J Barbour (c) DAS

Installing the antirockfall barrier before start (c) DAS
Installing the antirockfall barrier before start (c) DAS

With our previous references on the same cliff, we succeeded on that tender. A team of four of us equipped in two weeks an access on that remote part of the Nevis Bluff. From the top first. Then with Heliworks delivery, we were able to built a rock fall barrier above the area to be worked on. The installation of 120m of ladders and steps bridges allowed Fulton Hogan team and ours to gain access every morning, using a double fixed line system. For the following 5 weeks: hand drilling, blasting, hand scaling and helicopter watersluicing composed the program. Thanks to our ability and abseiling  skills, Drilling & Abseil Services has been a successful part of the operations involving helicopters, heavy traffic management and work at height. 

 Rock Bolting

Rock bolting after rock removal,credit Dave McKinney (c) DAS
Rock bolting after rock removal, credit Dave McKinney (c) DAS
Nevis Bluff, Queenstown side (c) DAS
Nevis Bluff, Queenstown side (c) DAS