Using Water Jets to Sink Piling in Lake Bottom.

[Richard]

Something a friend of mine passed on...

He owns a local marina so I put a bit more credibility into what he says here, than if the guy at Home Depot had told me this.

He said the best way to keep a dock from floating away during high waters was to anchor the pilings down using the screw type anchors (like used in mobile homes??)

He said that for those who anchor the pilings down, the docks are there for good, where-as if you don't do it, you run the risk of the dock being pulled out during high (flood type) water.

I hadn't thought much about this until my father in law happened to mention that OUR dock many years ago, right after they installed it, was lifted out by the high water and had to be reset by them (father in law & uncle in law).

I've personally never seen it happen, but the logic of the anchors makes some sense to me and would probably be well worth the "cost of insurance".


Richard

 

[DocHeb]

Thanks for the suggestion. Mobile Home Anchors would prevent upward movement, but my difficulty is preventing downward sinking.

I have seen A. B. Chance Helical Piers, and found the local contractor that installs them. He required test borings and an engineer's analysis, and then would charge $400 a piling to install them. This is a little much for a small boat dock on a 40 acre lake.

 

[8NTX]

I posted a similar thread before I built my boat dock, here it is

I got the boatdock and boathouse built - finally just paid the local contractor to pile-drive steel piers down (no floating boathouses allowed). I also posted a more recent request about pouring concrete underwater, since I need to sink about 4 more posts now that we have recently acquired a couple of jetskis and I didn't plan ahead. Want to do this job myself. Didn't really plan on getting these, but someone owed me money and offered them up - boss wanted them so now they're taking up space in my driveway.

 

[BXMMCC]

"I'm conceptually challanged on this - any chance you could draw a picture? "

I hope that the attachment works!

 

[Richard]

More dock quesitons before the water rises...

If one uses the "jet" method, what kind of water pump would you need? (I have a submersible pump I could use, I think it's about 1500 gal/hour???) not really sure on the volume, but it has either a 1 1/2" or possibly 2" outlet. It's currently used as the pump for our waterfall.

None the less, pops in law is thinking on adding a step to our dock and to do so, might be a good idea to add several piers. This jet method came to mind as I have the pump...(or should I just sneak the backhoe down & dig?) I was thinking NOT using the backhoe, cause we'll be using a 6x6 and the bucket on hoe is 2'. I figure, no need to tear up more than needed.

Also, how deep would you want/need to sink one?

Richard

 

[BXMMCC]

1500 Gallons/hour should do a fine job. Put them in as deep as the others.

 

[BigAl]

Hi ,
I forgot that on my little place in Panama ,the locals used a water pump to jet in my post for the dock/rancho /forums/images/graemlins/blush.gif I actually poured a 8' x 6"x6" steel rebar reinforced concrete posts in a wood form on dry land .I also had a tee about 2' up from the bottom . It looked like a giant concrete cross . After it cured in about 7 days ,the guys, (4 of them )set it in place in the water and using a water pump hooked up in reverse , just started working the post down into place .As the water jet blast blew the sand and muck out of the way the post went right down from its own weight . The tee acted as side stability and made the whole thing very stable .I think they had reduced the jet hose down to about 3/4 " piece of steel pipe about 10' long . I have had over 3000 pounds of cement stored on the rancho and it never settled or moved a bit !
I tried to add a picture of the rancho,with the post in place ,but I guess it is too big to attach .
Big Al

 

[Darren]

Don't use a water jet to set your piles if you have cold winters with ice formation on the water! I know some folks in the business and some do just that. It's not necessarily a problem with bulkhead piles because you obviously don't have ice on the land side. For a piling in open water where ice can form all around the pile, you may have a problem if the water level rises or falls when the ice is heavy. The ice will grip the pile and gradually jack it out of the bottom. Depending on how thick the ice is and the friction on the pile you'll see piles in the same vicinity get jacked up different amounts.

If you're in an area where you get thick ice in the winter with fluctuating water levels always drive the piles. You get better bearing capacity on the piles and more friction to resist uplift forces. I've seen docks on the Jersey shore which were really messed up after a hard winter. Those were the ones where the builder used a high pressure pump and a long pipe to jet them in. Typically the builder uses an excavator to move the pile into place while a laborer runs the jet. the operator will tap the pile a few times after it has settled as far as it can from the jetting.

The ones that didn't come out were driven in by a pile driver.

As for a pump to use if you live in a milder climate, the volume of discharge is not what's important. You need more pressure than a so-called trash pump will produce. I'd look at 2" fire pumps. You want something that will throw water quite a distance. You may be able to rent one.

 

[varmint]

I didn't see any mention of this technique in this thread, but here in Merryland, which has a lot of water-side installations, piles are driven by placing a vibrator head on top of the pile, turning it on, and down into a soft bottom goes the pile. No mess, no fuss, and it's done! Maybe a concrete vibrator would work for DIY projects??

 

[Darren]

That's also the method used for extracting piles. In some consolidated soils during an earthquake the soil can become quick (as in quicksand) greatly lessening the bearing capacity. A vibrating pile driver does the same thing as long as the proper soil conditions exist.