it can be rather amazing at times for me. i could swear i had everything nice and compacted even with using the 555c TLB. i can still get a descent amount of settling in areas.
it tends to be much easier to see settling, when you dig a trench with a backhoe. and a year later, you can see low spots. more so right after a heavy rain or during a heavy rain. you can see little ponds of water. just from things settle over the last year.
granted i am no PRO. be have learned the hard way. that any time i have to deal with loose material and have to compact it. that i should wait a year and at that later time expect to do a little more filling in with some dirt in low spots. every time i look on this farm or other folks properties. i can almost guess and confirm were i see cracked concrete drive ways, major cracks in paved drive ways, cracks in concrete floors. that they didn't allow for settling to happen. granted here in central, IL we see all seasons pretty good, extreme heat to extreme cold and wet weather in spring and in fall. with heavy snow in winters.
i always read 6" fill then compact then another 6" fill then compact. but for me, around here it is more like 4" fill then compact when using a hand stamper, and if 555c TLB then perhaps 7 to 8" fill then compact. and hopefully some rain between a couple layers or a sprinkle from a garden hose to wet things down some to help compaction. it really does not matter if it is clay dirt, or crusher run rock driveway, or sand, it seems about the same for me. i could be in a high dry spot on top of a hill or low wet spot or in between. and just a few feet difference in any spot can mean little setting to a lot of settling.
if i do no compaction what so ever. *ughs* it is a nightmare situation. if i want to drive over a given spot. and can quickly create a pot hole that turns into a mud hole that turns quickly into a "well poo need another tractor or vehicle to get unstuck. and fixing the area tends to be re-digging everything back out. and taking time to make sure i do a good compaction of everything as i slowly fill things back in. then give it a year to settle. and then do final adding of dirt in spots here and there if need be.
along with, if i do not do a very good compaction of things. when i go to re dig things back out. the dirt is much more heavier and wetter (due to extra water is being held within the dirt) i can tell there is more frost heave in winter also if i drive over this area in winter. before fixing it. due to there are more small speed bumps (for lack of better term) and low spots that suddenly show up once it starts getting colder. not due to driving over area and creating pot holes / mud holes. but just from frost heave. and not compacting the spot like i should have.
it is kinda a pain trying to learn how to compact things good. due to it can take up to a year to see results and perhaps longer for say a concrete floor / concrete driveway. to see full extent of settling. though generally after a year. majority of settling has occurred at least for me. and after the year, for me it is more about making sure i have correct slope and correct way to control were run off water goes. to keep wash outs from happening. and lesson amount of frost heave has on buildings and driveway.