the pit

Fancy digging a hole and filling it with concrete he said!
Turned out to be a base for a large tumbling machine, dig a 3m square hole 1.5m deep add a 300mm concrete base then 200mm concrete walls, stick a wedge of foam to the concrete and fill the hole with more concrete and bolt the machine to the top.
Theory is that the foam allows the large center block to move a little reducing the vibration transmitted to the surrounding floor.

Had a minor mishap, the concrete for the base turned up over 2 hours late and after we had said forget it and were packed ready to leave. We decided to stay late and get it done but that was the wrong decision as the concrete was old and very dry with a driver who was unwilling to wet it enough. This meant the poker was no use for leveling so we had to get in and tamp it. 15 mins and we could stand on it!! Unfortunately this meant we ended up with a rubbish finish.
Luckily for us the concrete company admitted liability and we dug it back out and started again. next load was great, poured wet, poker leveled it nice and we just ran a float over the top for a final finish.
When that was cured we set the wall forms in and made sure they stayed put by holding down with two 1 ton stillages of steel bars. Thats it for the moment as the company now has to make the chassis for the tumbler so we can cast it into the concrete.