Can you imagine the sheer size of the solar array and the amount of battery storage that would be needed to run a fleet of dump trucks on a minesite that runs 24/7 and these arrays and battery storage would have to be mobile because of the changing nature of developing Minesites.
We are talking trucks that can weigh 400t loaded going up and down ramps that usually have huge diesel motors driving generators to run the wheel motors at the moment, Where would you fit all the batteries needed to run the truck without compromising its carrying capacity?
Maybe a fleet of LV's could be run But the Big machinery would need a quantum leap in battery technology to run on electricity.
This is the largest dump truck at the moment.
 
Electric Mobility: World's Largest Truck - Mobility & Motors - Pictures of the Future - Innovation - Home - Siemens Global Website
It has 4 separate wheel motors that are powered by 2x 1,700kw 16 cylinder diesel engines, It will  take quite a few solar panels to run this puppy.