I have washed various pairs of heavy wool trousers and riding breeches in the past - both cavalry twill and Bedford cord, the latter being an 80% wool 20% cotton mixture. This was in a machine set on a very low temperature and using special soap for woollens (called 'woolite'). They were dried by spinning followed by hanging on a line. There was no shrinkage, but ironing them was a chore.
The low temperature is crucial - I washed another pair of trousers, a heavyweight wool twill, at a warmer setting, and these shrank to the extent that the turn-ups had to be turned down afterwards. There was also some mild fraying around the waistband, although that may have been present before the wash.
Overall, I would say this form of laundering is preferable to dry cleaning, but there are definite risks involved. I have an aversion to dry cleaning chemicals so consider the risk worthwhile.