Johnsonville Line Rockfall Mitigation

The Johnsonville line cuts up through the Ngaio gorge through 5 tunnels. Over the past 15 years, Abseil Access has helped Kiwirail reduce rockfall on various sections of the line and over the tunnel portals.

In 2019 AA conducted the 6th such project, installing active mesh and anchors between tunnels 1 & 2. The netting was installed first to reduce the chances of rockfall during the drilling phase. The team then use an A-frame drill rig to drill and install 32mm and 25mm diameter GRP anchors.

Image of the Johnsonville Line Rockfall Mitigation Project

The work included:

  • De-vege and rock scaling on specific line closure days
  • Working with Aurecon to design a constructible solution
  • Drilling 75mm holes and installation of 32mm and 25mm diameter glass reinforced plastic (GRP) anchors using a cliff face A-frame drill rig.
  • Installation of Geofabrics double twist PVC coated mesh.
  • Working under an active rail line with safety stop boards and rail protection.

All access was established from the top of the site reducing the need for hi-rail vehicles and rail closures. GRP bars reduced the electrical hazard risk around the high voltage catenary as well as eliminating corrosion issues. The netting was installed first to reduce the chances of rockfall during the drilling phase.

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Image of the Johnsonville Line Rockfall Mitigation Project
Image of the Johnsonville Line Rockfall Mitigation Project
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