Pile Driving Vibrations 5

[geodoc]

Piles will be driven within 10 to 25 ft of existing building. It is likely that vibrations from the pile driving will exceed allowable levels. Besides drilling the piles in, does anyone have any proven methods for driving the piles and keeping the vibrations to acceptable limits? Obviously, I do not want to damage the buildings but I also want a method that works so that the contractor does not have to stop because of vibration concerns. I have seen options such as drilling a casing to a predetermined depth (seems arbitrary), removing the soil, and then driving the pile. How effective is this technique? Any help?

 

[jrf]

We have used drilled shafts in situations where vibration was a critical consideration. You might also want to look at the Giken press in pile method. Essentially, it uses hydraulic jacks to push a pipe pile into the ground. Quite expensive, but it has been used extensively in Japan, where it originated. Fairly high capacities can be achieved as well, though not as high as with driven piles.

 

[cbosy]

Lukas and Gill wrote a great paper on this. They jetted the piles and performed compaction grouting adjacent to existing footings. Give me your fax # and I will send you a copy.

 

[Focht3]

Just be careful about any installation aids you use - jetting in particular. You could conceivably inflict more damage with these methods than with driving alone.

 

[RDK]

Do you have any limits on vibration? Is the building anything special in terms of susceptibility to vibrations? i.e. special process or equipment.

I’ve also seen blasting the foundations of a draft tube inside an operating hydroelectric plant. We just shut down the first couple of generators monitored the velocities. A lot of facilities are more resistant to vibration than you might think.

I’ve driven piles near fresh concrete and we used a blaster’s accelerometer. We arbitrarily set the maximum velocity at one half to one third of the legal maximum for blasting operations near buildings. I cannot remember what the numbers are but any blaster could be able to tell you. (It was a while ago and they tell me that memory is the second thing to go, I forget what’s first.)

Could you try driving one pile and check just what vibrations are caused and what are acceptable?




Rick Kitson MBA P.Eng

Construction Project Management
From conception to completion

http://www.kitsonengineering.com

 

[Qshake]

Since you noted in your post, I am interested in learning what the allowable levels are. As RDK points out all buildings and equipment/processes are different.

Some folks just shudder at the thought of those pile being driven anywhere near them.

 

[RDK]

See

http://irc.nrc-cnrc.gc.ca/cbd/cbd-e.html

Scroll down to CBD(Canadian Building Digest) #63 on balsting effects on buildings.



Rick Kitson MBA P.Eng

Construction Project Management
From conception to completion

http://www.kitsonengineering.com

 

[ttroy]

cbosy

I'm also looking for a copy of the Lukas & Gill paper on vibrations. Could you fax me a copy? We are having some controversy with potential vibrations to an adjacent structure in SF, CA. Fax 415-436-9077.

Thanks

 

[cbosy]

Coming at you.

 

[novs]

I recommend you do a building condition survey (video tape), before you drive piles next to buildings. It amazing how every tiny crack in a building can become your fault after driving piles, whether the cracks were caused by pile driving or not.

I know it doesn't answer your question, but its a little helpful advice.

 

[exploengineer]

Blasting vibration limits are normally based on a "Z" curve that includes peak particle velocity (ppv) and frequency. Blasting vibration frequencies are normally high in tight construction blasting, therefore PPV can be high. The normal exceptable max limit is 2.0 inches/second or 51 mm/sec. A good pile driving limit is 1.0 ips. This is extremely conservative.

Structural hairline cracking (75 microns or less) does not start occuring in concrete or mortor until about 6 inches/second or more with low frequency (below 20 hertz).

Cosmetic damage, such as nail pops in sheetrock, etc can start to occur around 4.0 ips depending on construction and vibration frequency.

I have been monitoring blasting and pile driving for many years and have never seen any real damage from either. Its more annoying then anything. Pile driving is much more annoying then blasting.

Remember, the closer to the structure, the higher the limit can be because frequency will be higher. When blasting in Manhattan, we sometimes are given limits of 3 - 4 ips depending on structure construction. The higher the frequency with low ppv = lower displacement.
Also, limits are like speed limits. Just becuase they are exceeded doesn't mean there will be damage. Especially with a low limit of 1 ips.

You can convert to acceleration by using the following formula:

(2pi (ppv)(hz)/386.4 = a

Displacement is the key, so if frequency is high with a low ppv, displacement is low. In pile driving, frequency is normally low (that's why its more instrusive to nieghbors), but there isn't much energy in the wave, so it attenuates quickly and is unlikely to cause serious problems.

Displacment = ppv/(2pi)(freq).

I hope my rambling helps.



Frank Lucca M.I.Exp.E.

http://www.terradinamica.com

 

[jheidt2543]

Exploengineer,

Why would blasting limits be higher than pile driving limits? From your last paragraph, the opposite would seem to be the case.

 

[Focht3]

[blue]Exploengineer[/blue] is correct, and his answer is consistent. Blasting involves very high frequencies (for the most part.) Pile driving frequencies are high, but not as high as those involved in blasting. The two variables that are involved in blasting - but not in pile driving - are the air pressure effect, and falling mass impact effect (when imploding buildings.) In my experience, the air pressure effect is the one that has a significant low frequency component that can be quite significant - and is often ignored. Geometry plays a role in the air blast effect - so there is no pat answer. Every case is unique -



Please see FAQ731-376 by [blue]VPL[/blue] for tips on how to make the best use of Eng-Tips Fora.

 

[DRC1]

The problem with blasting limts is that they apply to strucutural damage based on a few high speed high amplitude waves recived by the structure. It does not apply to soil settlement. Continous vibration at or near the resonant frequency of the soil will cause significant soil settlements at ppv's well below that neccesary to cause structural damage. However if significnat differential settlement occurs, it can cause strucural damage. Unfortuantly, there is not a lot of guidelines out here for limiting damage by pile driving.

 

[exploengineer]

Focht and DRC did an excellent job answering that question!

Thanks guys!

Frank Lucca M.I.Exp.E.

http://www.terradinamica.com

 

[agrant]

I have had good luck with helical (screw) piles in vibration sensitive situations. For examples look at:

http://www.atlassys.com/

 

[BKGOPARAJU]

I am responding to this rather late I guess.
I beleive the vibrations from driving or other machine bases can be intercepted or dampened before they reach an adjucent structure or foundation by using certain approaches. One of them could be using a cutoff trench to desired depth. The trench could be empty or filled with a bentonite slurry. I remember to have seen a study like this in Barkan - Dynamics Machines and Bases.

 

[KCBill]

I have been asked to monitor a historic theater for vibrations from the demolition of two adjacent building ( no blasting required) and excavation of the street between the old theater and the building being demolished. I have chosen to place two geophones in the basement floor and two on the outside balcony, both ajjacent to the demo going on. Can anyone help with criteria for damage?

 

[Ron]

KCBill....get a copy of Richart, Hall, and Woods text on vibration. There is a Response-Spectra diagram in there that lists the limits of damage to structures. I don't have a copy anymore or I would send to you.

You can also go to the Florida DOT website and get their criteria for limitations of vibration to prevent damage.

 

[dmoler]

Try predrilling a hole first to the depth required and then drive the piles, if pile is designed on an end bearing design. Friction would be reduced for capacities, but if the driving criteria is met, then the capacity should be ok. Predrilling should not cause vibrations to exceed threshold limits (0.5 ppv is my personal favorite).

The cut-off trench posted above is ok, but more difficult to execute properly.

Regarding effects of vibration, one resource I have used is the intro to FHWA Dynamic Compaction (download at

http://www.fhwa.dot.gov/bridge/geopub.htm,

scroll down to Geotechnical Engineering Circulars No.1) and NAVFAC DM 7.3 (I think a free down load is at vulcan hammer)which references some of that described above.