About thirty years ago whilst working on a sheep and wheat property in Northern Victoria I met a fellow (Jim) who was in France in 1914/ 18 and on Sunday's with a few beers he would talk of the war, there were a couple of things that he said that will stay with me for ever and one of them was that the large artillery shells would plug in the earth and then explode on a late fuse causing massive waves of mud that would fill every void (including trenches) as they went. A terrible outcome for the troops and one that I feel sure was unplanned by both sides.
Greg.