Anyone Have Any Soils Experience?

[vpl]

This is totally outside my area of expertise. My daughter lives in Tampa about 20 miles from the place where the sinkhole that just swallowed that guy in his bedroom. She called the other evening asking if there was any way to tell if a sinkhole was developing before it actually did. I have no idea about them more than what can be read in a Wikipedia article.

Is there any way to tell before the giant crater appears? (I know, this ranks right up there as stupid homeowner post ... which is why it's posted here and not in a technical forum.)

Please see FAQ731-376

 

[msquared48]

You should redflag this and repost in the geotech forum. Lots of help there...

Mike McCann
MMC Engineering

 

[zdas04]

I don't care if you post it both places. When you send a red flag to an anarchist he makes a shirt.

David Simpson, PE
MuleShoe Engineering

"Belief" is the acceptance of an hypotheses in the absence of data.
"Prejudice" is having an opinion not supported by the preponderance of the data.
"Knowledge" is only found through the accumulation and analysis of data.
The plural of anecdote is not "data"

 

[vpl]

Because it's basically a "homeowner" post I wasn't about to post in a technical forum. I've been scolded too many times! She's asked my brother (a construction architect in Florida) for his advice. He may know someone. And I actually worked with a soils expert here in Illinois ... but it's finding contact information, which I might try to do this weekend. Thanks though.

Please see FAQ731-376

 

[hokie66]

vpl,
As an engineer in another discipline, and a very active member as well, you would be given plenty of leeway in asking about sinkholes.

Florida sinkholes form in much the same way that most underground caverns form. Much of the state is underlain by limestone, which is soluble by water which is acidic, the more acidic the more soluble. Over time, voids form beneath the surface, and when one gets large enough, the surface layers collapse into the hole. As much of Florida at the surface is sand, there is little strength in the surface layers to bridge over voids.

As to predicting when sinkholes will occur, I don't know. Ground penetrating radar perhaps. Maybe Ron will chime in, or you can email him.

 

[Latexman]

Patricia,

My oldest daughter lives in Tampa too, and I admit I have the same concern. If you post somewhere else or learn something, please let me know.

Good luck,
Latexman

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[TheBlacksmith]

I took "dirt" in college, but we concentrated on glacial deposits, tilted strata and other "historical" issues that affected excavation and load bearing properties. It does appear that the ersoion of the underlying limestone (Florida is largely formed by billions of sea shells) is the causative factor. So, either borings to determine that there isn't limestone underlying your house or periodic surveys with either acoustic/sesmic methods (sonar) or ground penetrating radar to map the size, scope and progression of the erosion is the only solution. I think at this time, predicting eathquakes through GPS and strain gauges is more advanced than predicting sinkholes.

 

[waross]

Anyone Have Any Soils Experience?

I live in the country 6 miles from the nearest pavement and have an active seven year old son. My first reaction on seeing the title was, yes, lots. Sorry no sink holes.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[fattdad]

My advice if somebody was genuinly concerned and losing sleep would be to hire a geophysicist to conduct an electromagnetic survey and "look" for the signature of a void below the house. Can you do this right through the bedroom? Not likely, unless there's some crawl space and the workers want to work in the crawl space. You could do some lines about the house and see what they show.

f-d

¡papá gordo ain’t no madre flaca!

 

[VEBill]

Drilling a hole ("well") adjacent to the house should be relatively cost effective.

Other 'remote sensing' type options might (should!) be cheaper though.

The advantage of the hole is that it might provide an on-going zero-cost method to monitor the underground environment over the long term. Maybe.

 

[Ron]

Patricia,
Hokie66 is right in his descriptions. Most of Central Florida and particularly west Central Florida is peppered with sinkholes ranging from 5 feet in dia. to over 100 feet in dia. Sinkholes occur or have occurred in most counties in Florida, but the higher frequency is along the "Florida Ridge" running from about Lake City to Arcadia.

Here is a link to county maps of sinkholes....

http://fcit.usf.edu/florida/maps/galleries/sinkholes/

Predictability? Not good. Attempting predictability...relatively expensive and a shot in the dark for the most part. Ground penetrating radar has the better probability. Borings are almost worthless....the limestone under the surface sands and clays is so weathered that it has a poorly defined starting surface.

Ron

 

[IRstuff]

GPR penetration depth might not be sufficient, and requires scanning the sensor physically along the ground. An alternative is a seismic or ground resistance approach, both which can be performed with stationary stimuli and sensors and are used for oil exploration, etc. The former would be a "thumper" based approach, wherein something either thumps the ground or an explosive charge generates the ground waves. The sensors detect the seismic waves and determine, based on time of flight, what the ground characteristics are. The latter was pioneered by Schlumberger, and all I know of it is that it involves measuring the resistance of the earth.

Another possibility is to locate a bunch of accelerometers around your property to detect a before/all change in gravitational field strength. Once the sinkhole starts to form, presumably, the removal of mass under the sensor should cause a minute change in the local gravity field. Unclear what kind of sensitivity might be needed. Magnetometers might also do the same, but I'm not as sure of that. This might be the cheapest for a permanent installation, say, 50 sensors at $200 apiece, using either Bluetooth of ZigBee interfaces to a PC running possibly Labview (~$1500) to monitoring compare the readings, say, once a day.

TTFN
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[IRstuff]

OK, never mind the accelerometer; there's no sensor sufficiently sensitive.

TTFN
faq731-376

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[BigInch]

Geophones and a sledge hammer.

http://www.abqjournal.com/news/state/607481nm11-02-07.htm

Independent events are seldomly independent.

 

[stanier]

If in doubt move away. If you find a sink hole and then decide to move do you have a legal or moral obligation to tell the buyer?

“The beautiful thing about learning is that no one can take it away from you.”
---B.B. King

http://waterhammer.hopout.com.au/

 

[Ron]

stanier...yes. Legal. In Florida, the real estate disclosure laws are pretty clear. If you know and don't disclose....problem.

 

[IRstuff]

Some links about soil resistivity measurements:

http://www.cspg.org/documents/Conve...graphy_in_Identifying_Subsurface_Cavities.pdf

http://library.seg.org/doi/abs/10.1190/1.1441115

http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.135.2978

http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.28.1974

http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.56.9460

TTFN
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[BigInch]

I wouldn't think that resistivity of likely highly saturated soils would be of much use.

Independent events are seldomly independent.