Found an old dredge manual with a wild fact about sediment flow

I was cleaning out my dad's garage over the weekend and found a dusty 1978 operations manual for a 'Lakeshore' model cutterhead dredge. Flipping through it, I saw a section on sediment types that said something I had to read twice. It claimed that for a given pump speed, fine silt can actually move through a 10-inch discharge line almost 40% faster than coarse sand of the same volume. I always figured the heavier stuff would just push through quicker with more force. The manual explained it's about how the particles interact with the water flow and each other, creating less friction. I did a quick check on our current job in the Mobile River channel yesterday, and watching the slurry, it kinda made sense. Has anyone else come across this kind of counter-intuitive detail in the older books?

2 comments

2 Comments

elizabetht561d ago

That bit about fine silt moving faster really hits home. We had a similar head-scratcher on a project near Baton Rouge where the clay slurry just flew compared to the gravel mix. The old manuals get specific in a way the new digital stuff just doesn't.

spencer1991d ago

@elizabetht56 is right about the old books. They'd have charts for specific soil types you just don't see now. Our crew found a 70s field guide that broke down flow rates for Louisiana gumbo clay, and it was dead on. The new software lumps too much together as "fine-grained.