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Tunnelling a horizontal shaft through Sydney Sandstone

We are now involved in a small residential tunneling project in North Sydney. The owner is in his early 70s and knows that in the future the 38 steps from his gate to his door are going to become a really big obstacle. The project is to cut a tunnel through the rear of the garage under the front lawn and then under the existing lounge room, where a small elevator shaft will connect the vertical shaft to the horizontal tunnel under the front lawn. The project has been a hobby for the former mining engineer.

Due to the cost and time taken to excavate the first five meters of the tunnel we have been engaged to help. The challenge has been to fill horizontal and vertical holes using the chemical Expando. We initially used a grout pump to fill the horizontal holes but the cost of hiring was too expensive for this residential job so we came up with an alternative method.

We have been filling long skinny bags with the chemical Expando and forcing the bags into the horizontal holes using a PBC pipe and Timber ream it has had the same effect as if we had poured it into the holes from the top.

We are now far enough under the house that we can start cutting in the vertical shaft .Holes have been drilled up from the lower tunnel and as we remove the rock from the top we can simply drop it down the hole to be cleaned out through the garage. 

(Click on the images to make them larger)

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