What are the dimension of a standard dump truck?

First, you'd have to define what a "standard" dump truck is. I've driven trucks of all types for over a decade - including dump trucks - and have never known any to be standard. You have single axle dumps - which can be anywhere from a Class 3 to a Class 8 chassis - you have tandem axle dumps, tri-axle dumps, quad axle dumps, quint axle dumps, centipedes, superdumps (with a Strong Arm on the back), then you have tractor-trailer dumps, which could be end dumps, belly dumps, or side dumps.