There is some good info on jetting in the USACE Field Manual (FM) 5-134.  You can download a pdf from  http://155.217.58.58/cgi-bin/atdl.dll/query/download/FM+5-134.  Chapter 4 (Pile Installation Operations) has the info about jetting (p. 4-16).

The optimal way to do this is with a barge, derrick, and heavy duty equipment.  However, I've done ith several times with a rental trash pump and PVC pipe for a small-scale operation on the cheap.  Have learned the hard way how this works.

JB69 - I could not get your link to work. I am looking at jetting in 40 short pilings from 0 to 5 feet of water and already have the pump. Would love to hear what you "learned the hard way". is there a ratio of jet diameter vs. piling diameter?

sailorman2,

Sorry 'bout the link.  The USACE must have changed it, 'cuz it doesn't work for me now either.  Take a look at http://www.army.mil/usapa/doctrine/5_Series_Collection_1.html and search for "5-134", which is Field Manual 5-134. The site has all of the FM series manuals in pdf. The manual will tell you a lot about installing pilings and was very helpful to me.

We used a 3" pump several times for several different piling installation attempts, but I think, in retrospect, that a 2" would do fine and the water-filled hose would be easier to handle, 'cuz it gets very heavy. Water velocity is more important that gross flow rate anyway.

If you can figure out a way to hold the piling erect with the base on bottom at the location you want to install it, that's a good way to start.  I built a tripod out of 2"x4"x12' lumber with a triangular hole at the top and a pulley installed on the bracing on top for hoisting the piling and lowering it under some degree of control.  The legs were secured by eye bolts and rope around the outside of the rig.  

We were installing a 20' heavy creosote post with a bunch of fishing buddies using 19-20' boats.  We had 4-5 people involved and could not have done it with less, because of all the labor involved.  I think you could do short (<10') posts with 2-3 people, if you had a system worked out.

I made a 2"x10' stinger out of PVC pipe and attached a 2"x3" coupling so I could screw the stinger onto the end of the pump hose.  Other than the excessive weight of the hose the arrangement worked well.  You simply get the pump running well with a good flow rate out of the stinger, and raise the stinger to near vertical, so you can get a vertically-directed jet at the base of the piling.  The jetting action will create a sand/silt slurry at the base of the piling and you can work the stinger around the piling as needed to maintain the sediment in suspension.  The piling will advance into the deepening hole automatically from its own weight.  

We did it all with one pump and stinger, but two would probably work better, if you can swing it, so you can jet from both sides of the post.

During jetting, the intake hose was placed with a filter basket at some distance away from the piling location to minimize sediment uptake.

Short posts are a piece of cake.  Much deeper ones are a challenge, because you need a way to stabilize the long, heavy piling and you have to work with some sort of derrick, tripod, etc. to handle the elevation.  Also, you need to be able to adjust stinger length to get a longer one as you advance.  If you quit jetting to make adjustments, the hole closes in and it's game over, requiring you to start the hole over.

The other issue is the huge crater that's left when you get the post in place and it's at the proper depth.  We kept falling into the crater (3-4' deep) while working close to the piling. I think that it would be worth the extra step to have somebody carefully manage the intake hose with the sediment filter removed, and use it like a vacuum to suck up sand/silt and pump it into the remaining crater, filling it up to at least level with the bottom or perhaps above level. Then the fill should be compacted by stomping around on it or tamping the fill material with another post.

One of the downsides of jetting pilings is that the process destroys the soil cohesion, so backfilling a jetted hole around a piling leaves a much weaker piling completion than you might achieve by driving the piling.  I think the manual describes that specific problem.  So, anything you can do to improve the lateral strength of the piling foundation by backfilling and compacting would be helpful.

Hope this description helps.  Lots of luck with your installation and may Allah give you strength!

I recently sank 22 9" dia piles for a dock ranging from 8 to 20 feet long in 3-4 feet of water.  I have a method that works great in sand or mud base settings and can easily be done with two people.  My wife and I set all of ours (to a depth of exactly six feet) in just two days.

If some one is interested in doing this themselves just post a request and I will describe how its done.

Larry

Premium2000 I am interested in your method of pile driving
          thanks Shane                                                               

Larry - yes, would like details of what you did.  Souds just like I need to do.
thanks,
Ed

Doug,

Thanks for the info.

It is common in my area for dock builders to sink pilings using a barge for lifting and positioning the piling while using a water jet to work it to the required depth (6').

Since I don't own a barge and my wife is not strong enough to hold a 12' pile vertical for very long, we came up with this approach.

The key to my method is to shape the hole before handling the pole. To do this I built a light weight forming tool out of readily available PCV parts. Take a 6" to 4" bell reducer then further reduce it to 2".  Attached to this is a 6'section of 2" pipe, then a 2" te,e then another 4' pipe section.

I also built a jetting wand out of 1" pvc pipe. Like the main tool glue together a 6' section of pipe to a tee then another 4' section of pipe then a 1" pipe cap. Add a 2" threaded end piece to the tee as a connection point for the pump discharge hose.

The only other tools that are needed is a 5 hp, 2" dia trash pump (with hoses) and a chain saw, both can be rented.

The basic approach is to use the first tool to simulate the piling while hole is being formed. It then can be easily removed and the pile put it.

The tools were designed to create a 6' deep hole, 6-7" in diameter. I found that the hole created by the 6" reduced worked well for pilings 7" to 9" in diameter. You could use an 8" reducer if needed, the principles are the same.

Here are the steps involved:

1. Use the chain saw to pencil point one end of the pilings to be set.

2. Set up the pump in a small boat or floating platform with the suction hose/strainer in the lake.

3. Attach 2" pump discharge hose to pump and the center tee connector on the jetting wand.

4. Set main tool vertically at the desired location for the first plie.

5. Fire up pump and work the water jet tip around the bell reducer.

Note: throughout the process just let the water do the work, there is no need to pound the main tool up & down, be patient.

6. Keep the tees of the wand and the main tool lined up. This keeps the jet from getting too far ahead or behind the reducer.

7. As the sand/soil is being pumped out of the hole the main tool will just begin dropping under its own weight.

8. The tees give you excellent feedback regarding how deep the hole is at any time. Plus once they  drop below the water line you can easily feel with your foot how much further there is to go and exactly when the six foot depth is reached.

9. Once full depth is reach pull both tools out together with the pump still running.

10. Turn off pump.

11. Float the piling over and push the pencil point end down to the hole opening holding it there with you foot. Have you wife go to the other end of the pile and lift.

12.We found that once the pile reached 60 degrees it just fell in to place. You will be surprised how easily they drop into place.

13. You could go back with the water jet to adjust the piling height but we never found it necessary.

14. Once all the pilings are set, mark for level and use chain saw to top off any pilings needing adjustment.

That's it, this process was used with pilings up to 16' long with two people and I'm still married. Once you are set up each piling can be set in under an hour and with practice you could do them in under 30 minutes each.

That's about it. Good luck and please let me know how it worked out if you decide to do it this way.

Larry

Premium 2000

I am curious about what type of bottom conditions you had to set your piles in?  Once the guide bell was removed what amount of sediment returned/collected in the hole before you set the piling in the hole.  Also, how did you get the sand/mud to settle back around the piling and hold it once you had set it in the hole?  I am getting ready to build a dock in coastal NC and would appreciate any advice.

Sride,

Thanks for your question. I'm sorry about the delay in responding but I don't participate in this forum on a regular basis.


In my area of the country (western Florida)the soil is mostly sandy.  While hole will begin to fill in once the bell is pulled out it is a slow process which allows plenty of time to position the pole and drop it in.  If you are careful to keep the jetting wand level with the bottom of the bell then both will come out easily and if removed quickly, very little sand will be washed back in. If the jetting wand gets above the bell sand will be pumped over the top of the bell and make it difficult to get it out without working the jet back down.

Once the pile is in place the sand will begin to settle back in relatively quickly and whith an hour it will be pretty solid although the top of the hole will still be open.  It will take a month or so for the hole to cover over completely but as long as you don't jet down below the pile depth that you are shooting for then the the pile will be sitting on a firm bed and the sand that does fill in around the pile will do a good job of grabbing it so that you won't have to worry about it moving around.

By the way, if you do need to make pile adjustments side to side as you begin to assemble your dock, you can use a smaller jetting wand on one side or the other of the pile to adjust it's position. I just use 3/4 PVC pipe an isolation valve and my garden hose to do this. It won't take much.

Hopefully, this info will be useful to you.  Good luck with your project. Again I'm sorry that it has taken so long to repond.

Larry

Premium2000-Thanks for all the information.  I am getting ready to build a dock  off an inlet in Virginia (Chesapeake Bay area) with a mud/silt bottom and would love to get a look at your pvc tools if you have any digital pictures available.  I got a little lost in the building of the "tools" and it would be great to get a visual but if not I may just modify them as the concept confirms what I wanted to do.  Thanks again for the detailed information-David

Premium2000,
I would also like to see the pictures.  I need to start my piles soon.  Masterdavid97, I was just up in Crownsville. MD this WE getting my new (1974) catamarran ready for the trip to its new home in NC.  Ed

I no longer have the tools but what I will do is is amke up a quick sketch  and post that.  They are really easy to make and once you see the sketch it will be obvious.

Larry

Ok, I put together a sketch of the two tools that are needed for my method.  I could not figure out how to put it into this posting so I posted it on a photo sharing website for your review.  

If you go to "tlarry.photosite.com" and you will see the sketch which I prepared.

Good luck and please let me know how it works out for you guys.

Larry

Got it, thanks.

Thanks so much-If I can get things rolling I will try to do a photo journal to document my trials and successes but it may still be another 4-6 weeks before I even attempt to place the first piling.  Sailorman let me know how it goes if you get started sooner than that- my water situation sounds very similar.  Thanks again for the great and detailed info Premium.

Following the discussion re. jetting pilings with interest.Questions--does pump have to be trash?  What about semi or water pump.  How would method work on "dry ground", ie, jetting pilings for stairways, structures etc., where one has access to water for pump.
Bruce

Regarding the type of pump;  The amin reason for using a trash pump is that it can handle water sources that include small debre like many lakes and rivers have.  Other style pumps may work but could be dmaged in the process.  The other important factor is size.  A 5 hp 2" trash pump pushes a nice flow through the jetting wand.  Smaller pumps will work as well but it just take longer to evacuate the holes.

I don't see why this method would not work on dry ground. Some of the obvious differences would be the that the hole would likely have to be filled by hand once the post/piling was set. In a wet setting the hole tends to fill in itself over a shor time.  The other difference is how the piling is handled.  In the water, the pile can be floated out to the hole and it's apparent weight is reduced in the vertical position due to the bouyancy of the submerged portion. In some cases, where more of its length is below water than above you may need to hold it down and jet sand back into the hole to hold it.

The key here is to let the tools, the water and gravity do the majority of the work. Be patient, take the time to form a nice hole, and handle each piling only once & with the least amount of effort as possible.

Good luck!

Larry

Being new here, Premium2000's instructions are fantastic. Thanks for posting them!

MasterDavid97: Did you begin work yet? I also am in Norfolk on a small canal that is muddy/silty and would like to learn more about how deep you plan to set the pilings etc, as I am preparing to set pilings to repair rotted bulkhead and will likely add a pier to the new pilings. Any information on your research/findings on using this method in our neck of the Bay would be great!

Thanks
Scott