Okie's correct, lots of wedges needed at that size, and lots of muscle for elm. You may need to kerf cut it for at least the first split, chain saw or circular saw and be careful. I'd peel the bark and seal the ends plus about 6" of the trunk down from the ends. I would only split it in half for now and let it sit in a dry place for about six weeks to help prevent twisting when you reduce it further into more staves.
I have one about 8" in dia. that I cut 3 weeks ago and treated this way only I left it whole for now and no checking so far, just haven't had time to split it yet. Plus I know I'll likely need to be well rested before I tackle that job,