Air space under pole barn slab, mudjack or some other solution?

[Stinger]

I've found that the ground has settled a solid 2" (or shrunk when it dried out through the hot summer) on the SW side of my 60x44 pole barn. This building is 20 years old and the floor had no cracking until last year. Best I can tell the area where there is an air gap under the slab is about 30' along the 60' length of the West side of the building. I don't know how far under the slab it goes but the crack is about 8' from the West wall so I assume it goes at least that far. I was able to push a tape measure 2-3ft under the slab for the first 10ft or so of the wall, and then at another spot a little past the center of the 60ft wall.

The first picture is the corner post from outside (above the landscaping). The second picture is looking straight into the gap from outside, slab on top, dirt below.

The soil is pretty heavy in clay in this area (NW of Kansas City), not sure if that matters. One thing I noticed is it doesn't look like there is much/any gravel or other material between the slab and the dirt (or maybe it's all stuck to the bottom of the slab in this pic?

This corner is clearly settling as the door doesn't want to latch (it's about 3/8" below the striker hole), there are cracks/evidence of the west wall dropping down at least 1/2" in the drywall, and this crack showed up last year and is now getting wider. The ground in this area settled last summer/fall as well (I don't think it was this bad but the grass was overgrown here last year so I couldn't see it) and it seems to come back up in the winter or spring (door works better, dirt level is higher up the slab).

So my question is, do I call in someone to mudjack or polyjack this or is there a better solution?

Is it possible to lift the slab and hopefully get the wall back to its original location so the door will latch or is that out of reach and now I'm just trying to prevent it from settling any further? Thanks.

Any other thoughts/concerns I should be looking into here? Thanks.

 

[Stinger]

Nobody has any thoughts on this issue?

 

[sjvicker]

is it just the slab that's moving or are your posts moving too? In my little barn, if the slab moved downward from subgrade issues, the door would stay in place since its connected to the posts.

 

[Stinger]

It appears both moved, though at different rates. It looks like the posts moved more than the slab while the slab is doing its best to "float" above the sinking dirt. So the dirt moved the most, posts/wall second most, and the slab the least (so far).

 

[Stinger]

Do you need some other detail or did I somehow stump you guys?

 

[TurnipTruck]

Is it drier now than any time in the last 20 years?
Have you recently changed any drainage?

I have read of Texans having to keep the clay under/around their houses damp year round with soaker hoses.
As a test, you could soak the ground for a week and see if it closes up, but I suspect the disturbed soil was probably un- or under-compacted and mud jacking is now necessary. An experienced professional is needed.
A friend had a corner of his pole barn slab break and sink less than a foot and he had it foamjacked by a local business, but I haven’t kept up with how it lasted.

Caveats:
No personal experience with jacking, but I do understand the importance of compaction and how infrequently it is properly done.
No personal experience with clay soils either; we are surrounded by gravel glacial moraines.

 

[Stinger]

It's dry but not the driest in 20 years. It was actually drier last year.

Anybody have any input on whether mud jacking or poly jacking is better for this sort of problem? Looks like the "pros" in the area do one or the other, not both, so I'm afraid they will just say their method is best rather than getting an honest answer. I've searched about them both some but there are so many variables that determine which is best that I can't make a determination.