13/03/2024
Brynderwyns update: We're now in the third week of State Highway 1 over the Brynderwyn Hills being closed for critical slip repair work. Despite the weather roadworkers have continued hustling and our progress is still on track.
One major advantage of the closure is being able to work both day and night. As you can see in the first photo below, workers are busy onsite at night while most of us are sleeping—this photo shows them using a core sampling machine to drill five metres down.
Engineers then examine the core sample to see what condition the ground is in, including finding faults, seeing the depth of the underlying rock, and checking the underlying rock's strength and the rock's ability to hold to the planned horizontal nails used to support the wall or road.
The second photo is an example of a technique called "soil nailing", which is one of the main things we'll be doing to stabilise the slopes. This photo is of soil nails being installed on a previous site on the Brynderwyns in 2023, but it gives you an idea of what the work looks like.
Soil nailing involves drilling holes into the slope, inserting reinforcing bars, and grouting them into place. This helps tie the mass of soil together into a large stable block. A flexible reinforcing mesh is then fixed in place across the slope to help hold the soil between the nails together. Soil nails can vary in length depending on how deep the rock is at different locations—the nails we're using here will be approximately 15 metres long.
You can sign up for updates on our progress via email on our website: https://www.nzta.govt.nz/sh1-brynderwyn-hills/
For travel information about the closure, including on detour routes, check out this update: https://www.facebook.com/nztanorthland/posts/pfbid02ZiBpJV6QdYFDypdcQnMLyxRJXzp7ALpKgd7HpCnzziRZsGiVoT9pNtbeeKNBC5tKl
