Standard LMR-600 has a polyethylene jacket which should be OK for burial. I have about 150' run to the base of my tower. At my previous QTH I had about 250'. In both cases I ran it in conduit just so I could easily remove it if I moved since it's so expensive.
Clamp UHF connectors are available. The connector part number is TC-600-UMC. Please see http://www.timesmicrowave.com/products/lmr/downloads/28-31.pdf