Do you have a tractor with a back blade or front end loader? You could just push the manure loose from frozen base, then pick it up.
Other items to use if no machines, could be a thick 3/4 to 1inch steel rod, hit it with a sledge or heavy hammer, driving rod directly into the pile, break it apart in small sections. Pick axe if you can swing and hit what you aim at, will be faster than sledge method. Both methods reduce bigger pile to smaller size pieces by putting small metal tip end in, break the ice bond. Gives more force to small spot over shovel with wide edges, in breaking stuff up. WEAR safety glasses, goggles, for flying, frozen chunks that come loose. Frozen poop can hurt like rocks hitting you.
Wow, using all these FIRE based things in a dirt aisle, with lots of dust and chaff that “happens” without cement, seems like a real big danger to the BARN ITSELF! I didn’t notice any of them saying "Have your fire extinguisher handy while using blow torch, Acetylene torch, Salamander heater that have REAL FLAMES involved as they burn fuel!! You folks sure live to live dangerously!
Good luck OP. Tripping on that stuff is so AGGREVATING. I would be NOT happy with whoever let horse wander to leave piles in the barn aisle.
