I-35 is (roughly) a line of geological demarcation through Austin. Limestone to the west, black dirt to the east.
Set a 3' rod in 320lbs of concrete on a job back in October. Ran levels off known control, through it 7 times, most recently in January. Closed back at .01 or flat every time.
It's been an unusually wet winter. Contractor calls today. This rod in concrete is out in the middle of nowhere. Except it's 3-tenths higher than it was 3 months ago.
On the other side of town you could set a thumbtack in ng and it might hold for 30 years.
I recall Kent posting about setting 10' rods inside a sand filled pvc sleeve to achieve stability in your area.
Well, yeah. Wasn't planning on it being needed for too long. But will be driving something much longer in the ground tomorrow for the next couple months' work.
Perhaps all those earthquakes in Oklahoma are altering your reality as well.
http://earthquaketrack.com/p/united-states/oklahoma/recent
This is pure craziness. Putting California to shame.
Is the location soil a swelling clay that was dry when you set the BM and now wet?
Yep. Just, like I said, rained a ton around here the last few months. Don't think in 20 years I've seen one move this much. But we also aren't used to getting this much rain. Even some secondary stuff in the road has elevated a bit.
> I recall Kent posting about setting 10' rods inside a sand filled pvc sleeve to achieve stability in your area.
The rod that I've found to be fairly stable even in highly expansive clay soils is a 6.7 ft. length. I use regular 5/8 in. rebar, isolating the top three feet as follows.
Drive a three ft. length of iron pipe (with a cap threaded onto the top end to take the hammer blows. Then pull the pipe and drop a 36 in. length of 1/2" thin-wall PVC irrigation pipe into the hole. Stand the rebar up in that and use a combination of t-post driver and sledge to drive the rebar. In most of the black clays where I've set these, the last foot of driving the rod was work.
Take some care in selecting the site so that you choose a spot that will be fairly well drained, where there won't be standing water in the wet season.
Kent
The first part of that sounds good, but how do you get a 5/8 rebar in a 1/2 inch pipe? I know Texicans can do almost anything but that's kinda pushing it (grin).
Andy
< Ran levels off known control, through it 7 times, most recently in January. Closed back at .01 or flat every time.
> ...it's 3-tenths higher than it was 3 months ago.
Known control....is it exceptionally stable? Did you check into a third stable point to prove it's the TBM that moved?
Is the entire project area swelled up .3'? What happens when you set some stakes from this new stable TBM and the rest of the ground shrinks .3' when it dries out?
Just messing with you. Darn clay.
We have a local subdivision that every house has cracks in the walls that open and close with the seasons.
Certain times of the year, the windows actually open and close.
The garage doors mostly open and close.
Kent
> The first part of that sounds good, but how do you get a 5/8 rebar in a 1/2 inch pipe? I know Texicans can do almost anything but that's kinda pushing it (grin).
>
> Andy
Thin-wall irrigation pipe is sized so that it has a larger inside diameter than its nominal diameter. In other words, 1/2 in. thin-wall PVC pipe is usually larger than 5/8 in. id. I should say that it's also important to buy rebar that are are as round as possible, i.e. don't have projecting ribs on the side that stick out more than the deformations.
Are you sure the rod is 0.30 feet higher, or is everything else 0.30' lower?:-S
I did this today. 7' in. Never got too tough- it wasn't a hot knife through butter or anything, but it wasn't bad. Which makes me wonder if I shouldn't have gone a ways further.
I'm sure we'll find out if so soon enough...