The base of the hole that we have dug for the ground loops needs to be fairly flat and free of any large stones. This is achieved by what is called “tracking in”. This means using the metal tracks on the 14 tonne excavator to crush the stones by driving up and down. In our case, the sandstone underneath is fairly soft and seems to respond well to be “tracked in”.
After the bottom has been tracked in, around 100mm of sand is spread across the bottom of the hole. This prevents the pipework laying directly onto any large stones potentially damaging the pipes. Once the pipes are installed, another 100mm of sand will be put on top of the pipes before the subsoil is reinstated.
The hole at the moment is around 1m deep and covers around 750 sq m. This is only 2/3 of the area that we require for the ground loops. Once this hole has been covered over, we will dig underneath where the spoil piles are currently located. This will be approximately another 400 sq m. If I have got my maths right!
Even so, with a 750 sq m hole, it took around 40 tonnes of sand to cover the bottom. At the moment, it is starting to looking like a beach (and there aren’t too many of those in West Yorkshire!).
The ground in the foreground has still to be “tracked in”. This means using the metal tracks on the excavator to crush the stones in the bottom of the hole so that they don’t damage the ground loops when installed.
The base of the hole that we have dug for the ground loops is pretty rocky. The way to deal with this is to drive a 14 tonne excavator up and down. It’s metal tracks crush the stone underneath it.
Just a case of going up and down in a 14 tonne excavator until all the stones are crushed.
The ground loops will be put on top of the sand. More sand will be laid on top of the pipework before the subsoil is reinstated. This prevents the pipes from getting damaged.
We have used around 40 tonnes of sand in a hole around 750 sq m to get a depth of (roughly) 100mm. It is a lot of sand!