I was wondering if anyone does a "ground integrity" check to insure the earth under the out-riggers is stable first prior to a critical lift? Seems like in Florida it might be a good idea - Some type of X-ray or sonar thing ? - Great forum; learning a lot here !
I generally do a pre lift site visit if not familiar with the neighborhood . Scope it out & look for possible problem areas and that determines how much wood to load on the trailer if any . HeavyEquipmentForums US Army Corps of Engineers uses the sonar equipment . One system is a device they drag over the ground mapping voids & sinkholes . The other system is mapped out via aircraft . They fly over the area & sonar equipment in the plane can spot sinkholes . Don't know of a simple hand held device but would be handy if they made one . In my neck of the woods we do have allot of limestone bed rock and sinkholes . At the same time we are blessed with some tough old south Indiana red clay that helps keep it all from washing away . For the most part they are visible , but something we think about when setting up on pavement . You always wonder what's under the asphalt ? Good solid ground or are we going to punch through with an outrigger ? Good question Jimbo56 .
Something else we've done when questioning pavement / concrete integrity is drag short piece of 3/8 chain across it in an S pattern . You will notice a drastic change in the sound of the chain going from good solid base to a void of some kind .
Try it around the home or neighborhood sometime . It works , LOL !
Thanks - that's a great idea, low-budget and easy enough !
Your like some sort of a wizard TD :notworthy
LOL ! Redneck Sonar . Sold at your local hardware store , batteries not included .
Your thread reminded me of the man in Florida that was lost along with the home in a sinkhole . Think it happened back in 2013 , pretty scary ! We have a lot of underground caverns within the limestone probably similar to Florida only different soil type . First photo is an area in a pasture where the ground will open up & drop as surface water washes in . Hard to see the holes but they vary from 1 to 3 feet deep . Have to be careful when bush hogging . Second photo is an example of a sinkhole basin next to the wheat , strangely the basin has no open holes or sunken areas . It will fill with 2 to 3 feet of water if we get a quick 3 inch rain then slowly drain down in a couple day's . Would be pretty worried if I had to set up a crane on either area with what I see . Third & last pics are at spring house where the water flows out under a limestone bluff . It's water flow is all connected to the sinkholes via cavern . What's really interesting is the leading limestone edge off the bluff is damn near perfect level in all directions as most limestone seams are . Only thing I can figure is at some point how ever many thousand years ago water had to be at this elevation ( around 750 above sea level ) in order to lay the limestone level . I aint no geologist , just a hill jack that drinks water running out from under the rock Lost river runs through our neighborhood . It's interesting with part of it slipping under ground then resurfacing later to dump in to east fork white river . https://en.wikipedia.org/wiki/Lost_River_(Indiana) Tolliver Swallow is a good example of a large open sinkhole that is connected to "Lost River " . The picture don't due it justice . Been to the bottom of it myself , like climbing down a large funnel about 60 foot deep then see a cave opening in the limestone . http://www.nature.nps.gov/nnl/site.cfm?Site=TOSW-IN Kind of spooky feeling at the bottom of it . If they get a quick rain fall that fills it will see a whirlpool and loud sucking sound of the water headed to the underworld. Pretty wild ! Made me think of the old film " Journey to the center of the earth " .
What type and size of crane will you use? I've had great luck with the driving method, since tires have roughly the same ground pressure as pads. If you have issues driving on site, you'll have issues lifting on it.
The driving method works great on soft ground. But voids are not the same as soft ground. You can drive on top of a void, but once you put a huge weight on top of a void, it collapses.
My uncle is the VP of a large construction company, they are finishing up the Museum of African Americn history or whatever it's called in DC. It's a very unconventional building due to the surroundings and the water table. The lower levels are actually below the water table. Anyhow, they had to lower a railcar into the lower floor and had some big cranes on site, they used sonar beforehand for the entire project. He told me they were concerned about the Washington monument because they actually lowed the water table a bit when excavating for the project, the monument is already leaning I'm pretty certian. The entire building is more or less suspended from 4 (I think) large verticle columns that are well anchored into the ground.
Been hoisting almost 35 years, haven't experienced one of these "voids". We have more issues with clay and sand