Manure has creative ways of making our cleaning desires more difficult, that is for sure.
I am sure others might have better ideas but my first step in the removal of a pile that has managed to freeze to the ground is to kick it and see if it will pop off. This typically leads to a bruise on my toe or heel so I do not recommend this step.
Then I take out a claw hammer and I swing at the base of the pile with the claw side of the hammer and usually one or two good smacks pops that darn pile right off the ground.
If the pile is more stubborn than my claw hammer I admit that I typically give up.
I have one mare that likes to make a pile, then step backwards and stand on it while she eats from the hay bale, making the pile all rounded and totally fused with the ground. These sometimes do not come up well.
Edit to add - I have no doubt my neighbor must think I am very weird out there, hammering away at the ground.