Author Topic: suggestions for high-resolution tiltmeter (inclinometer) sensor?  (Read 51384 times)

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Offline ez24

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Re: suggestions for high-resolution tiltmeter (inclinometer) sensor?
« Reply #125 on: June 06, 2018, 03:30:29 am »
What do you guys think of this:

https://www.aliexpress.com/item/HACCURY-100-75-20mm-Stainless-Steel-Spirit-Level-Metal-Universal-level-for-Pump-ruck-Piling/32774959769.html


I think the 5  and 10 are minutes.  I like the looks, it matches the three windows that are from a Disney submarine (Florida).  One sub was dismantled and the others (13 or 14) went to other Disney resorts.  I got 4 windows and one seat.

It is hard as hell communicating through Aliexpress, so I need to confirm the 5/10 before I order.

If I get this, I will screw it to a piece of birch and set the birch with plaster of paris
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Offline JBealeTopic starter

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Re: suggestions for high-resolution tiltmeter (inclinometer) sensor?
« Reply #126 on: June 06, 2018, 04:35:35 am »
I could be wrong but unless it clearly says minutes, I assume degrees. If so your link shows a rather low-resolution device, looks like up to 10 degrees, and only one division per degree.
 If you want a 2D level, at least this one clearly indicates it has 4 divisions per degree (eg. 15 minute). https://www.aliexpress.com/item/HACCURY-High-Quality-Metal-Universal-Bullseyes-Level-Spirit-Level-bubble-Black-Color-accuracy-15-2mm/32832307350.html
« Last Edit: June 06, 2018, 12:10:12 pm by JBeale »
 

Offline rhb

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Re: suggestions for high-resolution tiltmeter (inclinometer) sensor?
« Reply #127 on: June 06, 2018, 01:10:56 pm »
I think the first one is intended for leveling RVs and such and is degrees.  The packaging certainly suggests an external mounting such as one would want in such an application.

The second one looks as if it would be great for setting up machinery to get it approximately leveled before switching to an arc second level.  Amazingly, just the vial alone is $1.98.

https://www.aliexpress.com/item/HACCURY-66-10mm-Spirit-Bubble-level-Degree-Mark-Surface-Circular-Level-Bubble-for-Measuring-Tool-Green/32789406307.html

This style would be easy to mount and not much more money than the bare vial.  Washer shims would level it quite easily as 15 minutes is about  0.007"  over the ~40 mm radius of the mounting holes.  Lapping washers to thickness on a wet piece of 100 grit wet or dry sandpaper on a flat surface (plate glass or stone countertop) would be very quick and easy.  Just wet the paper  down on both sides and do figure 8's with the washer until it's the required thickness.  The water on the back of the paper holds it flat to the surface very nicely.

https://www.aliexpress.com/item/HACCURY-90-17mm-High-precision-level-Construction-Machinery-Level-bubble-universal-protractor-Shell-Black-Bubble-Green/32668111401.html

For @ez24's application I think it's ideal.
 

Online Conrad Hoffman

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Re: suggestions for high-resolution tiltmeter (inclinometer) sensor?
« Reply #128 on: June 06, 2018, 01:33:19 pm »
Here's a possible differential screw arrangement- it turns out you can easily buy a straight 3/8 x 27 tpi tap. Never heard of it, but there it is. Make a bronze plug threaded 3/8 x 27 on the OD. Drill and tap it 1/4 x 28 (common tap). Knurl a section on the top to grip, or slot it for a coin or screwdriver. Put the plug in the plate you want to move (tapped), and attach a 1/4 x 28 screw to the fixed surface below. That will give you an equivalent 756 tpi adjustment screw. 27 tpi is a common pipe thread, so almost all imperial lathes will have a setting or gear for it.
 

Offline Henrik_V

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Re: suggestions for high-resolution tiltmeter (inclinometer) sensor?
« Reply #129 on: June 06, 2018, 02:02:53 pm »
ez24, I don't know how temperature dradients affect this, but I like the old idea of a hydrostatic hose balance.
A hose surrounding your building with 3 or 4 stubs at the corners to monitor the level.
(Water need some anti live/ant freezing components , and maybe a glycerin/oil topping to reduce vaporation)
Capacitive (or optic) level monitoring...
One could regulate the water level ( hose volume)  on one corner (if your house has corners ;) .. submarine windows sound geek ), so the others show the difference ...
« Last Edit: June 06, 2018, 02:07:28 pm by Henrik_V »
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Offline metrologist

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Re: suggestions for high-resolution tiltmeter (inclinometer) sensor?
« Reply #130 on: June 06, 2018, 03:26:33 pm »
Here's a possible differential screw arrangement- it turns out you can easily buy a straight 3/8 x 27 tpi tap. Never heard of it, but there it is. Make a bronze plug threaded 3/8 x 27 on the OD. Drill and tap it 1/4 x 28 (common tap). Knurl a section on the top to grip, or slot it for a coin or screwdriver. Put the plug in the plate you want to move (tapped), and attach a 1/4 x 28 screw to the fixed surface below. That will give you an equivalent 756 tpi adjustment screw. 27 tpi is a common pipe thread, so almost all imperial lathes will have a setting or gear for it.

Thanks, Conrad! Now you know my Logan has a quick-change gearbox with a threading range of 4 to 224 TPI, and it skips 27. I think my Jet is the same way, but it does metric as well. The tap would allow me to make a steel die, and that would likely serve well on a piece of bronze.
 

Offline ez24

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Re: suggestions for high-resolution tiltmeter (inclinometer) sensor?
« Reply #131 on: June 06, 2018, 07:28:19 pm »
I could be wrong but unless it clearly says minutes, I assume degrees. If so your link shows a rather low-resolution device, looks like up to 10 degrees, and only one division per degree.
 If you want a 2D level, at least this one clearly indicates it has 4 divisions per degree (eg. 15 minute). https://www.aliexpress.com/item/HACCURY-High-Quality-Metal-Universal-Bullseyes-Level-Spirit-Level-bubble-Black-Color-accuracy-15-2mm/32832307350.html

You are right !  :-+   At first they said 5'  but I wrote back and spelled out the words and they wrote back 5-10 degress.  So this is out.

The latest "in" :

https://www.aliexpress.com/item/High-Quality-Level-Vial-Bubble-Glass-Tube-Spirit-Level-Measurement-Instrument-5-2-mm-14-100MM/32879077293.html?spm=a2g0s.9042311.0.0.75ec4c4d4szs3u

What is really "good"  is this seller is the same (different company names) as the 4" 2mm x 100mm and Eric was concerned that I was getting my orders mixed up.  I am getting old (70) and senile so I really appreciate his checking on me.  So I ordered some 5' 2 mm x100 mm vials

I also ordered this

https://www.aliexpress.com/item/Full-Metal-Professional-Gradienter-Surveying-Camera-Tripod-Head-Measurement-Leveler-Level-Regulator-3-8-Screw-Mount/32334881870.html?spm=a2g0s.13010208.99999999.264.4c293c00RDugYc

I will take out the center screw and cork and fill in with plaster of paris that I will color with food dye.  I want to recess the vials and if I glue them, I do not want the glue to show.  Since the vials are bigger than this mount, I will have to figure the mounting after I get everything.

I want to make this look as good as I can. 

Thank you JBeale for starting this topic  :-+
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Offline metrologist

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Re: suggestions for high-resolution tiltmeter (inclinometer) sensor?
« Reply #132 on: June 06, 2018, 07:54:53 pm »
Thank you JBeale for starting this topic  :-+

Yes, and how is the electronic level coming along? Are you still measuring plate tectonics and the gravitational pull of the moon on your driveway?
 

Offline branadic

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Re: suggestions for high-resolution tiltmeter (inclinometer) sensor?
« Reply #133 on: June 06, 2018, 07:58:19 pm »
Why are you fixed on aliexpress? Ebay seller offers a UK located 3"/2mm vial, much more trustworthy.

https://www.ebay.com/itm/Ersatz-Wasserwaage-Glaslibelle-Blase-Empfindlichkeit-Feder-100x-9-5mm/132588613741

-branadic-
« Last Edit: June 25, 2018, 07:39:50 pm by branadic »
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Offline ez24

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Re: suggestions for high-resolution tiltmeter (inclinometer) sensor?
« Reply #134 on: June 06, 2018, 08:42:53 pm »

https://www.aliexpress.com/item/HACCURY-90-17mm-High-precision-level-Construction-Machinery-Level-bubble-universal-protractor-Shell-Black-Bubble-Green/32668111401.html

For @ez24's application I think it's ideal.

Thanks rhb but 1 degree is too much.   I calculate this is 2.5 inch drop at 12 feet.   I once had this drop and was lucky it was to the side so I used some 6x6s as shoring as I jacked it up.  It is 10x12 but 15 feet high (has a loft).  I was scared shitless and I do not want to go through that again.  I do not know what I would have done it was leaning over the edge of the canyon (cannot use shoring).  So with the 5'  and at a max of 10'  works out about 1/2 inch.  This is when I can start making plans to lift it.  It is a 1/2 day job for two people (for safety).  It takes 2 - 20 ton jacks to lift one side.  Two 12 ton jacks will not budge it.  I have a large collection of jacks  :-DD  One thing I have learned and that is how to move buildings.

Be sure to let us know what you do with your 4" vials.


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Offline JBealeTopic starter

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Re: suggestions for high-resolution tiltmeter (inclinometer) sensor?
« Reply #135 on: June 06, 2018, 09:22:30 pm »
> how is the electronic level coming along?

Several days of operation shows a big temperature-dependent offset. Likely related to my casual use of cheap hot-melt glue (I think it is 50% wax) to temporarily hold the capsule in place. That material has a huge(!) thermal expansion coefficient.  No time for experiments recently, but next chance I get, I will try some plaster for mounting instead.

Update: I did a comparison with an ebay 4"/2mm level and I believe the sensitivity of the prototype capacitive readout level is about 1" = 25 uV, while short-term noise = 2 uV rms so I have a noise level of about 0.1 second of arc (RMS), and maybe about 0.35 seconds peak-to-peak (rough visual estimate); not too bad. Longer-term drift is awful, but I hope to improve that.
« Last Edit: June 07, 2018, 05:00:04 am by JBeale »
 

Offline StillTrying

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Re: suggestions for high-resolution tiltmeter (inclinometer) sensor?
« Reply #136 on: June 06, 2018, 09:36:24 pm »
English version of brandadic's listing.
www.ebay.com/itm/Replacement-Glass-Vial-Spirit-Bubble-Level-nib-Accurate-100mm-x-9-5mm-Clear/142762523186

They do 45"/2mm which is still too sensitive for ez24 ?

"Thanks rhb but 1 degree is too much.   I calculate this is 2.5 inch drop at 12 feet."

On this round one, you'd quite easily see around 1/10 degree = 0.25 inch drop at 12ft ?
https://www.ebay.com/itm/Acrylic-Large-Spirit-Bubble-Level-GR-Liquid-66mm-Bulls-Eye-Bullseye-Vial-Round/132378829060
« Last Edit: June 07, 2018, 02:04:38 am by StillTrying »
.  That took much longer than I thought it would.
 

Offline ez24

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Re: suggestions for high-resolution tiltmeter (inclinometer) sensor?
« Reply #137 on: June 06, 2018, 09:38:19 pm »
...   I like the old idea of a hydrostatic hose balance. ...

Thanks

At first I did not like the idea of using a water hose because years ago I used a 1/2" x 100 ft clear hose that only lasted a couple of uses because of the minerals in the water coated the inside (I should have used distilled water).  But now I am starting to  like the idea.

I would use "funny pipe"  (the best flexible pipe there is) and some sort of glass tubes (the sun is hot is So Calif).  So as I wait and work on my 5' vials I will think how to do this.   I will mount them on the ground around the building.  I like the idea of having two systems, one inside and one outside.

I did not understand the pipette idea - now I do   :-+    I am thinking of using funny pipe (again the best pipe in the universe)  and somehow connect to pipettes  (the pipe comes with 1/2 pipe threads)  - install the pipettes in 2" ABS (protection from sun)  - cut slots in the ABS so I can see the pipettes.   Take 3 - 90 lb bags of concrete and put on the ground and drive a steel stake into the bags.  Wet the bags-  when hard - fasten the ABS pipe to stake - install pipettes   :-+

The ends need to be open for air so I need to figure out how to keep out the bugs  --  any suggestions ?

Boy I wished I had thought of this 20 years ago   |O

This is extremely important to me.  If this building (I call it the "villa" - because it cost me as much as a villa) gets out of control, I will have to sell my house.  The next buyer will tear down my house and put up a million dollar house (my house is crap but the land is valuable).  The villa will be worth keeping and with the house gone they could get machinery to the bottom of the canyon and brace the villa the correct way.   I once tried to rent my house out -  three parties came over and all they all wanted to see was the villa because it has an ocean view  -  the only ocean view I have

The reason I built a villa on a compost pile was because of the ocean view  (a big mistake)   At the time I did not realize how insane I am. 


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Offline ez24

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Re: suggestions for high-resolution tiltmeter (inclinometer) sensor?
« Reply #138 on: June 06, 2018, 09:50:40 pm »
Why are you fixed on aliexpress? Ebay seller offers a UK located 5"/2mm vial, much more trustworthy.

https://www.ebay.com/itm/Ersatz-Wasserwaage-Glaslibelle-Blase-Empfindlichkeit-Feder-100x-9-5mm/132588613741

-branadic-

I am located in Calif.  I cannot read the ad but I see a "  3" /2mm  ".   I think this is a typo.   I once saw this PIE vial on Aliexpress but I cannot remember the details.

I have had good luck with Aliexpress.  I believe blueskill said it was because they are closely regulated by their government. 

Because of my experience my ordering goes like this  1. Aliexpress  2.  Amazon  3.  Walmart   4.  Desperation   5.  Finally  ebay

Of course Chinese made stuff is Chinese made stuff.  I only use Amazon for expensive items.
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Offline ez24

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Re: suggestions for high-resolution tiltmeter (inclinometer) sensor?
« Reply #139 on: June 06, 2018, 09:53:23 pm »
> how is the electronic level coming along?

Several days of operation shows a big temperature-dependent offset. Likely related to my casual use of cheap hot-melt glue (I think it is 50% wax) to temporarily hold the capsule in place. That material has a huge(!) thermal expansion coefficient.  No time for experiments recently, but next chance I get, I will try some plaster for mounting instead.

Do you need any more 4" vials ?
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Offline rhb

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Re: suggestions for high-resolution tiltmeter (inclinometer) sensor?
« Reply #140 on: June 06, 2018, 11:07:15 pm »
Turn the pipettes tip up.   You'll need to check when reading them to make sure that the tips aren't plugged.  Mineral oil from the drugstore should be immune to most problems.  The graduation numbers will be upside down, but that should not be a problem as you will be interested in relative movement.  You're really concerned about the movement of the piers on which the house rests, not the house itself. As long as the piers don't move, movement of the house doesn't matter.  The piers moving does.  The ground the piers rest upon moving matters. That's one of the issues with using level vials in the house.  Houses are pretty flexible.  And piers can move even when the surface of the earth is not.  However,  if you have a water level on the house supports, a water level on the ground and a bubble vial in the house you'll know for certain what is moving.  It sounds as if you are adjacent to a cliff or very steep slope.  A water level on the ground near the house and one as far away from the cliff as you can get is important.  If the ground is moving underneath you, you need to know about it before there is a landslide, not when it happens.

I'd also suggest using PEX tubing, which is likely what you're describing as it has become very popular for plumbing.   Epoxy the pipette to a PEX fitting and then attach to the PEX.  I don't know how PEX does in sunlight, so a piece of black polyethylene to protect if from sunlight might be a good idea.  I have no idea what "funny pipe" is.  PEX uses brass fittings which are clamped to the tubing by a copper ring.

That round level I linked is graduated to 0.6" in 12 ft.  It's the same vial as StillTrying linked. So as a daily spot check you'll quickly notice if you've  had 1/4" movement in 12 ft.  In fact, given the sensitivity of the eye to circular centering, I suspect you'd immediately notice a movement of 1/8"  or less in 12 ft if you have it accurately centered.
 

Offline ez24

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Re: suggestions for high-resolution tiltmeter (inclinometer) sensor?
« Reply #141 on: June 07, 2018, 01:07:03 am »
English version of brandadic's listing.
www.ebay.com/itm/Replacement-Glass-Vial-Spirit-Bubble-Level-nib-Accurate-100mm-x-9-5mm-Clear/142762523186

They do 45"/2mm which is still too sensitive for ez24 ?

"Thanks rhb but 1 degree is too much.   I calculate this is 2.5 inch drop at 12 feet."

On this round one, you'd quite easily see around 1/10 degree = 0.25 inch drop at 12ft ?
https://www.ebay.com/itm/Acrylic-Large-Spirit-Bubble-Level-GR-Liquid-66mm-Bulls-Eye-Bullseye-Vial-Round/132378829060

Thanks  even 90" is too sensitive (I have a couple of these).    I have been looking at these bullseyes for awhile now.   Took another look at them to see how you can read 1/10 degree.  Since each degree has 4 divisions, the difference is 1/4 degree.  I think I could see 1/8  (I have an old set of eyes), so that would be good enough. 

I like this seller:

https://www.aliexpress.com/item/Circular-Bubble-Level-Spirit-Level-Measuring-Device-Krenometer-For-Crane-Size-90-17mm-1PCS/32837969646.html?spm=a2g0s.9042311.0.0.5a4a4c4dmmtNp5

So I ordered this - I think it a better fit for the tripod head than the 100mm 5' vials.

I will use the 5' vials for a x-y measurement.  This will help determine how much to raise end side.  The circular will help me to place concrete bags at the bottom.  The pipettes will show what the earth is doing (not always the same as the villa).

 :-+ :-+

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Offline rhb

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Re: suggestions for high-resolution tiltmeter (inclinometer) sensor?
« Reply #142 on: June 07, 2018, 01:22:50 am »
I *really* want to emphasize that the major issues you face are soil compaction under the foundation and incipient slope failure (aka landslides).  You really need to measure both using a fluid level system.  Measurements in the house with a level are just a convenient means of alerting you to the need to check the fluid level measurements.  You cannot accurately measure soil compaction and ground movement with a level vial. Fluid level systems are the *only* thing that will handle those issues appropriately.  A high resolution tiltmeter will tell you something is happening, but not what.

There are solutions to soil compaction, but incipient slope failure is really expensive to mitigate.  If you detect that it's time to sell.
 

Offline StillTrying

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Re: suggestions for high-resolution tiltmeter (inclinometer) sensor?
« Reply #143 on: June 07, 2018, 02:02:32 am »
Yeah, all the round ones are 60mm dia, and 4 divisions per degree, = 0.625 inch at 12ft.

This one is very cheap for me, the 2nd pic is 70mm across on the screen, I measured it, and the 1/4 deg. divisions are very clear, although not the bubble.
https://www.ebay.com/itm/Bullseye-Spirit-Level-Large-Round-Circular-Bubble-Vial-60mm-Caravan-Furniture/222588993994
I've never had any problem with fleabay from here, even when it's a gift from HK(2 weeks), never used CH.
.  That took much longer than I thought it would.
 

Offline ez24

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Re: suggestions for high-resolution tiltmeter (inclinometer) sensor?
« Reply #144 on: June 07, 2018, 02:05:31 am »
You're really concerned about the movement of the piers on which the house rests, not the house itself. As long as the piers don't move, movement of the house doesn't matter.

There are no piers, the villa sits on bags of concrete or whatever I can get under it.  A bag is 3 1/2 ",  a 2x6 is 1 1/2 inches.  I also use 3/4 and 1/2 plywood.  I designed the villa to be movable.  I built it 12 feet from its current location and moved it with rollers made from 2 " pipe filled with concrete.   This was a major error.  It moved 6 feet by itself toward the edge of the cliff.  It stopped 2 feet from the edge.  Years later I watched a house move and they said that was very very very dangerous, I know.  What they do is put rollers under one side and jack up the other side with hydraulic jacks at an angle.  If done correctly the jack will slip off at the correct time.  If not they push it off the jacks.  Very safe and clever.  They got a 2,000 sq ft house within 1/4 inch where it was suppose to go.  Once the building falls off the jacks it will not move.

It sounds as if you are adjacent to a cliff or very steep slope.  A water level on the ground near the house and one as far away from the cliff as you can get is important.  If the ground is moving underneath you, you need to know about it before there is a landslide, not when it happens.

Yes to very steep slope, but there is bedrock 12 feet away where I can place the reference level.


I'd also suggest using PEX tubing, which is likely what you're describing as it has become very popular for plumbing.   Epoxy the pipette to a PEX fitting and then attach to the PEX.  I don't know how PEX does in sunlight, so a piece of black polyethylene to protect if from sunlight might be a good idea.  I have no idea what "funny pipe" is.  PEX uses brass fittings which are clamped to the tubing by a copper ring.

I have a 100' roll of 1/2 PEX but funny pipe is better (immune to the sun) and can be buried.

https://www.toro.com/en/professional-contractor/irrigation-sprays/super-funny-pipe

I use this for everything outside and in 25 years not one failure.  I have a 150 foot line hooked up to a hose bib faucet at 100 psi for over 20 years now and in some areas it is exposed to the sun.

That round level I linked is graduated to 0.6" in 12 ft.  It's the same vial as StillTrying linked. So as a daily spot check you'll quickly notice if you've  had 1/4" movement in 12 ft.  In fact, given the sensitivity of the eye to circular centering, I suspect you'd immediately notice a movement of 1/8"  or less in 12 ft if you have it accurately centered.

I bought it.  It will be the go to level.  The 5' vials will be a double check.  The pipettes will monitor the hill.

Now I have a question about taking pictures and will post a question about this

thanks
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Offline tomato

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Re: suggestions for high-resolution tiltmeter (inclinometer) sensor?
« Reply #145 on: June 07, 2018, 02:26:47 am »
There are no piers, the villa sits on bags of concrete or whatever I can get under it. 

Have you thought about putting some piers under it and stabilizing it? People add basements under existing houses, so adding some piers for a 10' x 12' building should be pretty straight forward.
 

Offline ez24

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Re: suggestions for high-resolution tiltmeter (inclinometer) sensor?
« Reply #146 on: June 07, 2018, 03:25:39 am »
There are no piers, the villa sits on bags of concrete or whatever I can get under it. 

Have you thought about putting some piers under it and stabilizing it? People add basements under existing houses, so adding some piers for a 10' x 12' building should be pretty straight forward.

Impossible  There is at least 6 feet of concrete rubble under it.  I cannot access it with machines.  Wished I could but I would have to go down at least 20 to hit the bedrock then drill into the rock because it is on a slope.

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Offline rhb

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Re: suggestions for high-resolution tiltmeter (inclinometer) sensor?
« Reply #147 on: June 07, 2018, 11:59:17 am »
From the description it sounds as if you have several issues:

The soil is compacting under load.  This can be particularly severe if it has high organic content.

The soil is being pushed down slope by the load.

The soil is moving down slope under its own weight.

The first two can be mitigated by increasing the surface area upon which the structure rests.  The last can only be resolved by piers drilled into bedrock of sufficient strength to resist the shearing force of the soil.  It also resolves the first two.

In many respects, pouring a larger, heavily reinforced  concrete slab adjacent to the villa and moving the villa onto that might be the best option.  One could bore piers with a portable auger 6-10 feet and fill those with concrete and rebar tied into the rebar in the slab.  That will mitigate near surface soil compaction and also the effects of expansive clays. It won't stop the movement, but would slow it down a great deal.  The slab will still move, but with piers under the house which rest on the slab, compensating for the movement just requires jacking and inserting a shim from time to time.  Once the house is resting on the new slab, cast concrete piers in place with a steel plate on top.  Every  time you get 1/8" of settling, slide a sheet of 1/8" plate on top of the stack.

Of course, all this is speculation without pictures of the situation.

 

Offline JBealeTopic starter

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garage floor tiltmeter output this morning 7-June-2018
« Reply #148 on: June 07, 2018, 06:02:44 pm »
In case of interest, here's the output of my garage floor tiltmeter this morning starting at 7:10 am.  One vertical division (20 uV) is just under 1 arc-second, per my very rough calibration.  The time axis units are hours. After sunrise as things warm up, the output drift becomes large, which you see towards the right. There are some other interesting features:

Time        Event
----------------------------------------------------------------------------
0.77     a large spike from my weight as I walk right next to the sensor
0.86     small ~0.4 asec tilt up from car in the driveway leaving
1.14     ~3 asec tilt down from car in the garage leaving, with slow recovery
1.4 - 1.8   about half-hour of increased noise, as slab adjusts to departure of car (?)
----------------------------------------------------------------------------

The thing I'm now curious about is that time interval for about a half-hour starting at t= 1.4 with increased noise, maybe 0.3 asec or so. This is not a one-time event; I have seen a similar period of such noise starting after the car leaves the garage, having been parked for some time. I wonder if it's related to the concrete, the soil underneath, or something else.

 

Offline rhb

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Re: suggestions for high-resolution tiltmeter (inclinometer) sensor?
« Reply #149 on: June 07, 2018, 07:30:35 pm »
Very interesting.  ez24 sent me a couple of the 4"/2mm vials which arrived today.  No copper foil tape though, so it will be a while before I can replicate this.

The rebound after the car leaves is the opposite of what happens when a load is a suddenly applied to saturated soil. The noise may be related to ground water movement.    The behavior is similar to backpacking mattresses with light foam and a air tight envelope.  If you just open the valve it will gradually inflate itself, but with a very small pressure differential the flow is very slow.  The pore spaces in the soil need water flow to expand.

If it is caused by movement of water it will correlate with changes in the weather. The effect will be stronger after rains and weaker during dry spells as the zone of saturation moves up and down.

It will be interesting to see what the arrival of the car in the garage looks like.
 


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