Ground bearing test for Passive slab foundation
A requirement of the foundation design for the house is to establish the soil type and bearing capacity through core drilling and a ground bearing test. This then allows the structural engineer to design a suitable slab and sub base for the house. Certain soil types such as clay can be problematic for a slab and generally require a larger reduced dig and a thicker build up of sub base to avoid heave under the slab.
Soil analysis drilling rig
A small rig was brought to site to undertake a ground bearing test by driving a hole into the ground down to 4 meters, and to also bring samples of the soil up to the surface for visual inspection and collection for lab testing.
I was fully expecting to find rock chalk at about 1.5 meters as this is what we have at the top of the garden. It was quite a surprise to find silty chalk with blue clay beneath it. Our plot is at the bottom of the valley where sediment must have formed and is at a junction of rock chalk and sand with a seam of clay running through it.
It came as quite a shock to see bent coat hangers being used to check for underground cables and pipes. I am not sure I would rely on it 100% but he did find my underground mains power cable and also water connection to the house.