As I see noone has tried to help you with this inquiry after many days, I will offer the following comments. As Archimedes' principle is a fundamental law of physics/fluid dynamics, it is kind of hard to "avoid" buouyancy at least when fluid conditions exist. However, this does not mean that measures cannot be taken to avoid such environments and e.g. flotation. While I don't know specifically about "code" requirements in this area, I am however aware of the Steel Tank Institute and the guidance e.g beginning on page 42 under the heading "Flotation" at https://www.steeltank.com/Portals/0/pubs/Welded%20.... This Institute may be a good contact.

• Assume the soil is water.
• The volume of the tank as equivalent water becomes the buoyant force.
• Subtract the weight of the empty tank.

The difference defines the concrete slab needed to keep the tank under. Don't forget to add concrete to offset the buoyancy of the concrete, size the straps for the load and apply safety factor.

Due to degradation of our industry, most tank manufactures have this canned and often provide counter buoyancy packages.