I use my bike for geocaching. That means that sometimes, I'm going diagonally across a muddy field. And that's English mud, not your wimpy foreign stuff. Mud that attaches itself affectionately to your wheels, rides up into the rest of the bike and slathers itself over everything. It also builds up on your boots, so on every step you're lifting several pounds of mud, and walking a few inches higher than you expected.
Geocachers (are there any here?) will probably recognise this situation.
If the mud is the soft, clingy kind, then is builds up on the wheels, after some yards it jams into the caliper brakes, and eventually gets so thick that I can't even push the bike, let alone ride it. I have to stop every 10 or so yards, dig out the mud, then I can do another 10 yards. The alternatives are A) carry the bike (and that's maybe 80 pounds), or lift the front wheel and drag the back along (it won't rotate because of the mud).
Eventually, I arrive, exhausted, at the other side of the field, and hopefully I'm not faced with another field just like it. Then I can spend several minutes removing twenty pounds of mud before I can continue using it as a bicycle, and not just a very heavy thing to carry.
When I get home after a route like this, I take the power-washer to it, and hose off all the mud. I'll try to remember to take a picture of it next time.