The maximum dual axle dump load is about 10 cubic yards. Anything larger is going to be an 18 wheeler or dump truck with a pup trailer
I purchased about 4 million dollars worth of dump trucks over a 14 year time frame. I purchased the maximum size heavy duty dump trucks with dual axle, Freightliner or International chassis, equipped with Mercedes Benz or Cummins diesel engine. The maximum large capacity dump bed is 12 cubic yards however that would be if you filled and packed the bed with materials then smoothed the load off to be exactly level from front to back. Since a front loader can’t make the load exactly level, most loads end up averaging of about 10 cubic yards.