Vibro hammer piling into silt sand

[bennytrfc]

I am currently involved in a project where we will be using an ICE Model 223 vibro pile driver. We are installing interlocking U-section steel piles into silt/sand material with SPT between 35-50. The hammer is old and the company has no records of it being used in the past, what we are trying to find out is whether this hammer is capable of driving into these soil types. I have attached the hammer spec. Any advice would be greatly appreciated.

 

[SlideRuleEra]

I am not familiar with this particular hammer, but in general there is not a true "Yes/No" answer to your question - just the usual "Maybe".

The real question is not only CAN the hammer do this, but how efficiently can it be done. Having driven piling as a Contractor in the long-ago past, I can assure you that it is very possible to install piling with a hammer that is "too small", but what Contractor can afford to stand-by all day (literally) to drive one sheet?

Sorry that I cannot give you a better answer, perhaps someone else can - just want offer this suggestion so that you get the information you need to make an informed decision.

http://www.SlideRuleEra.net

 

[vulcanhammer]

There are many "rules of thumb" out there to size vibratory hammers. Some of them can be found at

http://www.vulcanhammer.info/vibro/Vibrator.pdf

I should emphasise that these are just that: rules of thumb. Selecting a vibratory hammer is very much an experience based business.

The document you referenced is damaged, but ICE's site has the specs at

http://www.iceusa.com/223-335e.htm

What's very interesting about this hammer is that it is a "high-frequency" hammer. I outline our (Vulcan's) experience at

http://www.vulcanhammer.info/vibro/

We saw these hammers used in cohesive soils very frequently, but the big drawback to a high frequency hammer is that the amplitude isn't as great for the same dynamic force from a lower frequency hammer. That amplitude is important for elevated toe resistance, even with low displacement piles such as sheeting. In that situation a lower frequency/higher amplitude hammer will use the whole pile as a rapid impact hammer; the longer the "stroke" (amplitude) the more the system can overcome toe resistance.

Another important factor is the water content of the soil. A saturated soil will facilitate vibratory driving at any frequency, particularly with cohesive soils.

 

[Zambo]

On a previous project constructing a jetty to a river we used an electric vibro for installing sheet piles. The soil was silt and we were driving to length.

Rate of installation was good but at some locations we could not drive the full length. All piles were either fully or partially installed using the vibro. We then brought in a pneumatic hammer to complete the driving where the vibro had been unable (or just too slow) to drive the full length.

 

[BigHarvey]

With N = 50 it is very unlikely that you will succeed in installing your sheetpiles. You can help with jetting but it is definitely simpler to use first rhe vibrohammer and then finish with a diesel or hydraulic hammer to drive the sheetpiles to their final depth.
Do not forget that the vibrations caused by the vibrohammer will compact the soil furthermore if it is a clean sand ( which is likely to be given the N values )

 

[lallatin]

From the minimal description of the project regarding penetration depths, other than the pile section, I am assuming that you are talking about shallow depth, ie in the range of 30'. What is the waterlevel? Any deeper, and BigHarvey is probably right. For shallow installation, that hammer will probably work. We need more details.

 

[ShawnR]

The ICE 223 vibro is a high frequency vibro that was designed to excell in sandy/ silty soils. The 223 is a high speed version of the standard frequency model 216. I have personaly witnessed these two hammers used on the same jobsite with an amazing difference in performance. The contractor was pulling sheet piling in a seawall that had laid over towards the ocean. They were using the 216 and it was taking them over an hour to pull one single sheet. The interlocks were getting cherry red and the sand was being blown out of the area around the interlock due to steam being generated under ground from the high heat. Once the contractor recieved the ICE 223 vibro on site, they were able to pull a pair of sheets in less than 10 minutes. They then used the same hammer to re-drive these same sheets to build the new seawall. The sheets were about 35' - 40' and were being pulled and driven in beach sand in Sandbridge VA.

If you are only driving you may want to ask ICE to supply you with a bias weight for the hammer. This is a saddle weight that fits over the suppressor housing and helps the hammer drive a little better. Since it is on the suspension, it acts like a crowd force on the gearbox. In my experience, these weights cost very little to rent or purchase. If you are renting the hammer from them you may get it thrown in for free.

Good luck. Let us know how it goes.

 

[ozziz]

Need some help on this matter on a sheetpile retaining wall. The bending moment is not very high and therefore a light Section will be sufficient. But I am afraid that the sheetpile will buckle due to driving in medium dense silty sand N=25 at lower layer. Can anyone advise where I can find information on suitability of piles thickness or Section modulus to overcome the driving stress in denser layers?

 

[PEinc]

ozziz,

Are you a contractor or a consulting engineer? If an engineer, talk to a local pile driver for recommendations or specify a minimum section modulus and let the contractor pick the sheet size he thinks is drivable. If you are a contractor, you should already have a feel for the needed size. If you are a contractor and will need to buy the sheets, pick a heavier sheet that can be extracted and then be re-used on most other projects. If you intend to rent sheets, your choice will probably be limited to heavier sheet sizes. Suppliers usually do not rent light weight sheet piling.

 

[ShawnR]

That vibratory hammer you mentioned, the I.C.E. 223, has low amplitude and high frequency. It would be very gentle on the sheets.