Hi all.

I am trying to model some soil substrates in to my site model, I have made topo surfaces of design and existing levels.
I also have a few bore hole locations, and what I am trying to do, using the borehole data, is interpolate my substrate levels.
This has proved pretty difficult, as I don't have a 3D TIN file of this data, I have a total of 2 bore holes on the particular part of the site I want to do this on, and also I cant give any depth to a topo surface so building this as a topo surface given that my data is too limited, and I need different substrates to be different materials, and varying thicknesses, I dont think a topo surface will behave as I want it to..

I have tried modelling these as a floor, and changing the materials to be sand, clay, rock, etc.
This works to a degree, but where I have for example, a substrate that is 500 deep at one point, and 100 deep at the other, I'm finding the floor just cant handle the volume changes in between.

Is there an easy way to model substrates that I don't know about?
How are other people doing this, and what are some good solutions please?