My land was once part of Camp Fannin, a World War 2 Army base to train soldiers to fight in Europe. It was only open for a few years and it covered 14,000 acres. They trained 100,000 soldiers every 3 months, and this included small arms rifle ranges on up to large howitzer type cannons. The shape of the range was kind of like the capital letter C. All of the shooting went into the center of the C shaped range. I have rifle range number 4 on my land.
Once the US Military owns or leases a piece of land or building, they are responsible for contamination on that land for all eternity. Around 2017 or 18, funds where made available to clean up the bases of old ordinance, and 1,800 acres in my area was part of that clean up. The Army is in charge of this, but a contractor is doing all the work with former DOD experts from the military. They create a grid, then clear the land, then go over every foot of it with metal detectors. If they think that they have found old ordinance, they blow it up. This happens every day at around 3:45 pm. Not exactly, but pretty close to that time every day. Some days, they might set of something earlier, or even three times in a day. Most of the time, it's a dull boom. Every know and then, it's massive.
From what they told me, when the war ended, the Germans held prisoner here where used to walk over the range and identify all the ordinance. The sooner they finished, the sooner they got to go home. They rushed it and missed a lot. Since then, stuff appears out of the ground. I've seen rocket grenades in person, and pictures of cannon rounds on peoples land. It just slowly works it's way up to the surface, and then one day, it's just laying there, or sticking out of the ground. Most is harmless and rusted away. Some still has TNT in it that has gelled and turned to Nitro Glycerin, which is very dangerous. I'm not aware of anybody actually getting hurt, but the Army guys did start out doing this with just a couple sand bags and plywood over what they where exploding, and then one day, they blew up something much larger then expected and it really scared them. Now they really pile up a lot of material on top of their explosives before detonating it!!!!
If there is an old military base close to where you are hearing explosions, this could be what's happening. I know that they have been doing it all over the country, and not just from WW2. Before coming to my place, they worked on a Civil War site.