We installed riprap at the east end of the driveway culvert. The 60 pound bags get very heavy by the end of the day, especially in the Florida heat and humidity.  We used the tractor to dump a pile of fill behind the bags, and shovel it in as we were going. We tamp the fill every layer of bags to prevent settling and shifting. To lock it all together every three courses we drive two rebar two foot long through each bag at an angle into the bags below.