Monday 7 August 2017

Building the road

Part of creating Mt Chocolate has been constructing a private access way in from Severn St to the future house and art studio. This road is 100m long, is built on clay and includes a turning circle.

A lot of time was spent in the last 24 months, scraping off the top soil for use elsewhere. This soil is a kind of peat and is not suitable under roads but great under trees. The clay however is quite hard and packs down well.

During the rainy months, especially winter, the clay gets very wet and goes puggy making use of heavy machinery difficult. All I had to use was a 1.5 Tonne digger (Back Hoe).

I went and talked to road construction workers in the area and watched while they worked to get an idea on how to do the job. I also asked 2 civil engineers for advice.

The common suggestion was to use "Base Course" from Edendale. This is basically big round river boulders and stones. It packs down very hard, but requires a bulldozer to shift and compact. It has to be delivered by very large twin axle trucks which would chew up the wet and now softened clay.

The solution I came up with was to use AP65 Dunite, an Olivine rock from a Greenhills quarry near Bluff. A 200mm layer of AP65 would need to be laid on top of Bidim Geotextile roading fabric which would lie on the clay. Another 50mm layer of AP40 Dunite would be laid on top of the AP65. Finally a layer of "Top Course" which is fine Dunite.

The small digger bucket could handle the quarried Dunite because of it's jagged shape.

All of these layers needed to be carefully laid using a small truck that carries 3 cubic meters, or 5.4 metric Tonnes. The truck driver had to back in and tip the aggregate without driving on the fabric. The small digger was placed on sheets of plywood on top of the Geotextile on top of the wet clay. The digger bucket was then used to pull the aggregate back over the roading fabric.

Everything was compacted as it was laid, first using the digger, then our 2 ton Toyota Prado, and finally the fully loaded delivery truck. The road will be compacted even more when the clay dries out in Summer.

The road is 4.5 meters wide and is 80% completed.

The whole job has gone really well. Not bad for a total beginner.

A big thank you to Chris the truck driver who delivered the aggregate, and Dave for the loan of the digger.