Nice find John, If anyone is interested, an NAA file (control symbol: 51/1/209) shows photos of the "dugout" as well as similar ones the Army used at the time to test how the explosion may have occurred.
here's a photo of the dugout where the explosion occurred:
Good on the "Strine" for digging up this tragic event. maybe it won't be forgotten again now that it is back in the national psyche.