Is a dump truck considered a tractor trailer type vehicle?

Well, dump trucks range in size greatly. You can make a dump truck out of a one ton pickup truck, if you so wish. The US truck classification system lists a Class 8 truck as being anything over a 33,000 lbs. Gross Vehicle Weight Rating. 33,000 lbs. is the max allowed for a two axle unit, so, basically, any tandem axle vehicle (and all tractor trailers) are going to be Class 8 trucks.

However, the licence class in the USA is different. Most Class 7 and Class 8 dump trucks can be driven with a Class B CDL. However, if that dump truck is going to be towing a trailer rated at over 10,000 lbs., then the same Class A CDL required for a tractor trailer will be required to operate that combination of dump truck and trailer.