Around my area, new railroad ties are pretty expensive. I don't know what you are planning to use the railroad ties for, your post gives no hint about the design of your structure, but conventional construction in Massachusetts for such a building would involve sonotubes filled with concrete for supports, then framing elements (2x10, 2x12 depending on span), with conventional framing.
There is no problem installing sonotubes on clay, provided the clay is sufficiently strong. Again, you give no hint about the type of clay, strength of the clay, moisture conditions, so there is little I can say about your case. However, most clays I have worked with are adequately strong to support a lightly loaded building such as you describe on sonotubes. There are ways to test the strength of the clay, which I could describe if you provide more details about your design.
There is no problem installing sonotubes on clay, provided the clay is sufficiently strong. Again, you give no hint about the type of clay, strength of the clay, moisture conditions, so there is little I can say about your case. However, most clays I have worked with are adequately strong to support a lightly loaded building such as you describe on sonotubes. There are ways to test the strength of the clay, which I could describe if you provide more details about your design.
