Is there a resource where I can find out how much force is required to dig into different types of earth.?

If you mean with backhoes and such, no. There are way to many parameter that would need to be taken into account and the particular value you ask about would serve little to no purpose. The information wouldn't be worth the effort to publish yet alone accumulate. The operator learns by experience how many yards in differing types of bulk material he'll be able to move in a day which is the value important to him.

An idea may be gained of the relative force necessary from soil bering capacity charts if that helps.

That helps a little but those numbers are way low for penetration of the soil. even the largest value would work out to 41 PSI. I'm very familiar with the parameters of diggers, dippers, drags etc. What i'm interested in is related... sort of... I guess I could make a tool and measure how much force is required to force it into the ground and take it to different types of soil. I was hoping there might be a standard of sorts out there somewhere.. SAE maybe