Skip to content

Makorori Hill Slip Repair – MagnumStone™ Gravity System

Facebook
LinkedIn
Twitter
WhatsApp

Project Details

Contractor

Client

Engineer

Location

Cirtex Regional Contact

Oakley Currie

Oakley Currie

Project Information

A major weather event in May 2022 caused a landslide near Makorori, about 10km east of Gisborne along State Highway 35. A large piece of highly saturated farmland slipped onto the Highway and covered one lane, reducing traffic to the East Cape region.

Earthwork Solutions was required to clear the slip from the road and secure the slip area to prevent it from causing more damage. The hillside contains internal springs and fissures, so it needed to be benched and well drained before stabilisation measures could be introduced. One supporting measure was creating a solid retaining wall structure between the base of the slip and the road. This would prevent any further slippage blocking the highway while giving a solid platform for all work done above.

DESIGN

Cirtex was approached to provide a robust, quick-to-install solution to this retaining wall structure. A 100m, 2.5m highMagnumStone gravity wall was designed, which could easily be installed once enough debris had been cleared. With the simple ‘slot in place’ extenders, a design was created using MagnumStone’s design software. Cirtex gave the design engineer training over Zoom and collaborated closely with them to produce the design. With time pressure to get the road cleared as soon as possible, securing this workable solution allowed the design engineer to concentrate on desaturating the hillside, knowing there was a robust solution in place to reinforce the first zone and stop the slip from creeping forward toward the highway.

Placement of the MagnumStone wall close to the curb would allow more support to be built into the hillside stabilisation. The MagnumStone gravity wall system was the ideal choice to not only lock the lower tier in place, giving support for the bench layer above as the contractor looked to secure the hill, but also safely separate the construction area from the main highway so traffic could continue.

In an emergency repair such as this, the flexibility of MagnumStone’s design also allows it to easily be extended should signs indicate that more reinforcement is required along the road.

INSTALLATION

Commencement of building the MagnumStone wall was dependent on enough water being removed from the hillside before installation could begin. All crews were required to have completed their drainage tasks on the front section. During excavation,the top of the hill started to slip again, and significant rain events continued to hamper initial progress. Construction of the MagnumStone wall finally began in early July 2022, and because of the relative speed in which the blocks can be placed, the wall itself did not take long to construct.

Thanks to Cirtex manufacturing and storing large quantities of MagnumStone at the production facility in Kopu, stock of both MagnumStone blocks and extenders had already been shipped to the contractor’s storage facility, which meant there were no delays when the contractor was ready to install. Should more reinforcement be required, or if another slip occurred, the contractor did not have to worry about the immediate supply of MagnumStone to site. This was a crucial factor in getting both lanes of the road functional as quickly and safely as possible.

Compared to a Mechanically Stabilised Earth wall, MagnumStone’s gravity wall system with the use of extenders is the fastest construction method. The large blocks are lifted into place with the use of a 5 – 8 ton excavator, with the extenders simply slotting into place. The contractor quickly worked their way along the 100m stretch of road, preparing the base before adding each section of the MagnumStone wall. The bank was then hydroseeded, with the road opened to traffic, giving unobstructed access to the East Cape once more.

The MagnumStone system used provided the following benefits to the project:

  • MagnumStone’s flexible design methodology allows for variable ground conditions
  • Quick and easy installation makes MagnumStone ideal for rapid response slip repairs
  • MagnumStone can be placed close to curbing to allow for maximum land stabilisation

Project Video

Products used in this Project