I’ve seen projects where the soil investigation report classifies the soil type as class M. I would automatically assume to follow the corresponding table of AS2870 for class M, and that’s it, I have the design of the foundation (Slab on grade with internal and external beam), of course satisfying other requirements from AS2870 like the section 4.5.1.
However, I see designs for class M that use screw piles which confuses me, when can I use the prescribed table of AS2870 without worrying if I need screw pile. And in the design of screw pile, do I consider the slab and edge beams to be suspended or shall I consider the stiffness of the soil?
Hey @VirtualEngineer ! First of all welcome to Blueprint! Look forward to having some good chats on here
Let met start by saying I’m far from an expert on Australian codes or geotechnical questions. But we had a good discussion in the team on your question about screw piles with the AS 2870 prescriptive tables. From our perspective, if you follow the tables “by the book”, you shouldn’t need to add piles. That said - it’s quite possible that experience with your local soil conditions or other site parameters mean that designs fare better with these piles or that the prescriptive provisions don’t apply. I’d suggest consulting with a local geotechnical engineer for more information.
