setting pilings

[MoJ]

I plan on building a small dock. I need to set 2 pilings in the water. The water depth where they'll go in is approximately 2 feet. It's a freshwater lake with a typical mud bottom and coarse gravel mixed in.

How would I go about setting the pilings? Depth under the lake bottom? Concrete around the base? Working/digging underwater? What material would I use for the pilings?

Any thoughts?



Jason

 

[LandCruiserPhil]

Just a thought...set a sonnatube as deep as you can, pump the water out, remove what ever material you can, drive rebar into the ground as deep as you can, pour concrete.

disclaimer - I know nothing about water and docks, I live in AZ

 

[Japan4X4]

You will not have to remove the water if you pour concrete into a sono-tube. Also driving rebar into the ground will result in rusting rebar and spalling concrete.

If it is a mud bottom drive steel pipe piles. Maybe 6" dia or so. Drive them hard and as deep as you can. But I think this is beyond the average Joe kind of thing.

disclaimer - I know a lot about piles and have three engineering degrees directly related to this field.

 

[photogod]

Get a powerfull pump. the type used by fire departments to pump out basements or farmers to irrigate fields. Lay the intake in the lake suspended above the bottom with large cinder blocks so as not to suck iup the bottom sand and mud. Put the exit side of the pump hose right next to the item you want to sink and start the pump. The pump blows out the sand a gravel and the pipe or pile will sink in the hole at the same time. When you have the pile set to the proper depth, pull the pump out. I have seen tons of wood piles set this way and have worked on projects and done it myself. It works like a charm. As a sideline, wood works really well for this application and will not rot above or below the water line, just at the water line. Don't let the DNR catch you doing this as it is prolly very illegal to sink piles in a lake for permanant use. Most of the docks up north use a log cabin approach for dock support and then fill them with boulders for streingth and lay the dock leingths on top. Good luck.

Disclamer - I have no engineering degree in piles but this way really does work! All of these piles were put here like the above mentioned 35 years ago.

 

[Kofoed]

Sonatube is cardboard, basically, and lined on the insde. Unlesss they have models that are lined on the outside, it will disintegrate in water fast. Even then, the end will not be lined.

I work on jobs that use drilled, cast in place concrete piles under fresh and saltwater. Typically, you set metal casing, drill/dig out the center, drive the casing in farther, and repeat. Pull the casing as the concrete is poured.

I would definitely set the piles in concrete. Use 3000 psi mix, minimum, lean. Place the concrete from the bottom up. The concrete will displace the water. The top of the concrete will be mixed with mud and thinned out becuase of the water. Let this flow out past the bearing part of the pile.

You can try to do this by hand, or rent a bob-cat or back hoe with an auger attachment.

As for as the rebar, you can go with epoxy-coated rebar to minimize corrosion. Maybe a little over kill, unless you want to drive it directly into the soil.

I would try for a 24 inch hole, at least 3 feet deep.

As this is probably over-kill but......

 

[beaufort-fj60]

I'm on the coast and do a lot of layout for dock contractors. they have three basic methods for setting piles. The piles they all use are treated 25-40' poles (like a short power pole). they are naturally tapered because they are trees. they first take a chain saw and cut an angle on the end going into the ground. The setting methods are 1.) auger drill, done close to shore, 2.) vibrate / tamp the pole midshore 3.) drive / tamp pole with a track hoe on a floating barge. I doubt you want to do 2.) or 3.). The auger works great, but remember piles should be driven to refusal. If you auger, put pole in hole and beat the crap out of it with a sledge hammer it should work great. I have seen some "backyard" illegal docks use a water hose and slip a pile into the ground. You basically dig a hole with the hose and the pile slowly slips into this hole.