When the only tool you have is a hammer...

You really need to go to the flea market. Amongst the other tools I picked up was a cold chisel. While digging out one of the pilings in my backyard, I ran into a series of tough roots. The smaller ones split under the shovel, but the thicker ones just sheared off a layer and stayed put. Cold chisel plus hammer plus two or three taps at each point on the root equals no more root.