Serious builders around here use pea gravel tamped. If you put your time in by hand or with hydraulic tamper they are as solid as quick crete. Set several hundred railroad ties when I was growing up, either fence corners or corrals. Most still in the same place since mid 60's. 8' ties, and Dad always said, "what extra is sticking out of the ground don' do you any good" so for corner posts it was always 4' deep if we had to bust rock for 18". Corral ties usually 31/2' deep. He was a meticulous fencer, unlike some of the neighbors. They never had to chase any of our cows out or bring them home. Kenny Rogers coulda played his 4 wire like a bass.lol
