I am in the process of digging the footings for a slab extension.
The soil is very sandy. We are on top of a sand dune about 100m from the beach.
I have started digging the trenches for the beams out first but then I have to cover the flat part of the slab foundation with a layer of gravel and sand compacted with a motorized roller or vibrating plate. The problem is that I expect the vibration to cause the gravel sand and my existing soil to slide into my trenches.
The question is
Do you think compaction will fill my trenches?
Should I compact the soil first and then dig the beam trenches?
Should I use formwork on both sides of the trenches and then remove the formwork from the inside of the trenches before pouring the concrete?
All advice is welcome please