Wave Generation from Pile Impact 1

[WARose]

I am looking for some info (preferably empirical/measured) that gives the types of waves (i.e. compression, shear, Rayleigh, etc) produced [red]within[/red] a pile during driving. Based on some other info I have, I suspect the vast majority would be compression waves......but I am interested in finding more info (and getting quantities).

By the way, I want to emphasize I am not interested here in waves in the soil produced from driving.....[red]only the pile itself[/red]. (I have plenty of info on the soil aspect already.)

Thanks.

 

[berkshire]

Warose,
There was a man named Arthur Stinner , who wrote a paper on some of the work done between, the first ,and second world wars, by the late Barnes Wallis. The large bombs he produced during the war, were based on research work he did, on shockwaves in pilings during the construction of the Waterloo Bridge in 1935, one of his inventions that came out of that, was the deadblow hammer.
While I do not think this is an answer to your question , it might point you in a profitable direction.
B.E.

http://www.arthurstinner.com/stinner/pdfs/1989-dambusters.pdf

You are judged not by what you know, but by what you can do.

 

[WARose]

Thanks but that's about a million miles from what I'm looking for. Fortunately, looking harder today, I think I've got some better leads.

 

[Okiryu]

WARose, have you tried at the Vulcanhammer website?

https://vulcanhammer.net/

 

[WARose]

WARose, have you tried at the Vulcanhammer website?

One of the first places I tried.....but didn't see anything. But I am finding other resources.....will advise on what I find.

 

[WARose]

Ok, I found a variety of info. Ref. 1 & 2 came up with a (3D) solution to the problem. It produced a number of wave types: longitudinal, shear, Rayleigh, von Schmidt, Love, etc. Even looking at the stress outputs, it's not 100% clear how much wave production per type there is. What is clear is: for long periods of time the traditional 1D longitudinal wave theory is sufficient. For short times various other waves (especially von Schmidt waves) are significantly impacting results. Also apparent is the production of Rayleigh waves on the surface of the rods. (It should be noted that the vibratory phenomenon is more pronounced in rectangular bars than circular. [Ref. 3].) Radial displacements seem to approximately correspond to Love wave theory in Ref. 1.

This still left me with part of my original question unanswered: how much of each wave? Given the math of some of the sources was impenetrable, I fell back on another source: the solution to a circular disk siting on a homogenous half space. (I.e. something typically used to represent dynamically loaded foundations.) Results show (in such a case; see Ref. 4) that at low forcing frequencies (and for a Poisson's ratio of about 0.33), Rayleigh waves can take up as much as two-thirds of the waves produced by power transmitted (7% P-waves, S-waves transmit the rest). However, at high forcing frequencies (like impact), the power is almost entirely transmitted by P-Waves and S-Waves. (The vast majority being P-waves.)

While this may seem to be a inappropriate comparison at first......Ref. 4 states:

"Very high frequency vibrations can radiate only vertically downward without spreading; in effect they are confined within the prismatic "rod" of soil directly under the foundation......The physical reason why the importance of Rayleigh waves diminishes with frequency is quite simple . The depth of penetration of the Rayleigh wave....is about one wavelength beneath the surface (skin effect). The power propagates towards infinity through cylinders of this depth and ever-growing radius. Because the wavelength is inversely proportional to the frequency, the cylinder "surface infinity" becomes flatter and flatter as the frequency increases; and the window through which the power must pass closes to a circular slit."

That helps explain some of the wave production I see (away from impacted [rod] ends).

If I find more....will post.

------
References:

[1] 'Wave Production in a Thick Cylindrical Bar Due to Longitudinal Impact', by; Vales, et al., JSME Journal, Series A, Vol. 39, No.1 1996.

[2] 'Wave motion in a thick cylindrical rod undergoing longitudinal impact', by: Cerv, et al., Wave Motion 66 (2016), p.88-105.

[3] 'Impact: The Theory and Physical Behavior of Colliding Solids', by: Werner Goldsmith, Dover books (2001), p. 30-31, 43-44.

[4] 'Foundation Vibration Analysis Using Simple Physical Models', by: Wolf, Prentice Hall (1994), p.115-118.

 

[Lomarandil]

Good stuff WARose!

----
The name is a long story -- just call me Lo.

 

[Okiryu]

Hi WARose, looks like you spent good time researching for this. Also, thanks for sharing the references. Is this part of university's research?

Also, I do not want to divert your post but since you are looking for waves during pile driving, have you seen in your references any relation of the produced waves with buckling of piles during pile driving?

 

[WARose]

[blue](Okiryu)[/blue]

Is this part of university's research?

No. (I'm long gone from my college days.) This came about for 2 reasons.....first, I've been reading a lot about wave propagation problems lately. And secondly, I visited the site of a client about a week ago. While there, he passed along a contractor's complaints about steel piles vibrating laterally too much during driving. (Fortunately, a project I had nothing to do with.) He asked the why of it......and among the explanations I shot out was: the waves produced during driving (in the pile) have lateral motion components that (at the right frequencies) can be noticeable.

But that left me wondering (not for the first time) about quantities produced (of each wave type) in such a situation.

[blue](Okiryu)[/blue]

Also, I do not want to divert your post but since you are looking for waves during pile driving, have you seen in your references any relation of the produced waves with buckling of piles during pile driving?

Not that I saw. Most of my references stay in the elastic range.....however Ref. 3 deals with the plastic wave front.

 

[dlawrence529]

Check out GRL's website. Most of their software is based on waves propogating in piles. They publish a lot of papers and give a lot of presentations to promote their software.

https://www.pile.com/reference-papers/

 

[WARose]

Thanks dlawrence529. It's been my experience however that most of those WEAP programs consider the production of longitudinal waves only. But I will look at it when I get a chance.