Dynamic Probing 1

[MarkDK]

Hi all,

I am looking for information about this testing equipment. Has anyone used it before?

I am interested to find out the manufacturer's address, calibration - conversion to SPT, and case studies been carried out using this equipment .. etc.

Your help would be appreciated.

Cheers

 

[BigH]

What is the specifics of "dynamic probing"? Can mean different things to different folks. Can't tell you a thing about "this" testing equipment as we don't know what it is - same with manufacturer's address et al.

 

[MarkDK]

Thanks,

It has only one meaning "it is a test that can repalce the SPT" which is the standard penetration test, widely used for site geotechnical investigations.

Cheers

 

[soiledup]

BigH,

I'm guessing that MarkDK does not come here very often

Soiledup

 

[Mccoy]

MArkDK,
you evidently mean dynamic penetrometer but they come in different sizes and fashions (and energies).
The only suggestable one is the one meant by BigH, the DPSH (dynamic penetrometer super heavy) with hi impact energy.
Much used here in Italy, in the Pagani website (one manufacturer) there are studies on efficiency ratio plus correlations with SPT in a couple of test fields.
DPSH (and other dynamic probes) are usually correlated to SPT, which has an average reliability of 25-40%. So, a correlation of another not-too-reliable correlation is bound to be unprecise.
Pagani studies highlight a few weak spots about this device. In my opinion, that's a rare example of scientific honesty coming from a manufacturer!!

 

[dgillette]

Are you talking about the Dina-Star?

http://www.tecnotest.it/pdf/ING/chap_8_eng_pages/pg126-132_eng.pdf

 

[PSlem]

I had found info on a site on liquifaction, but the link was no good a year later. Basically it was a Copco gas powered breaker with an accelerometer. I would check the SGI site for links. Swedish Geotechnical Institute.

 

[BigH]

To be honest - the SPT is dynamic probing at its most simplistic! I was wondering if he was thinking of the DCPT - which of course means different things to different folks - my heavy weight pentest to the TRRL miniature dynamic cone; then there is the seismic cone penetration test - or geophysical methods or . . . "and the beat goes on . . . ."

 

[Mccoy]

dgillette,
it's not the dinastar, the relevant Pagani link is the following:

http://www.pagani-geotechnical.com/english/RendimentoDP/RendDP.htm

guys around here are using it with decent results, in cohesionless soils, at relatively shallow depths and with a torque sensor.
You might use a casing, but I never heard of it done in practice.

I think this gear is, energy-wise, one step down the Becker hammer or the Japanese Large penetration testing device, they use in gravels.

I would love to see the results from LPT in some familiar gravel layers where the usual dynamic tests yield high or very high blowcounts. Is that friction angle really so much large???

 

[MarkDK]

Many thanks to the people who replied to my query.

I recently found other sources of information such as the;

http://www.coreprobe.com/

http://www.roehren-hamm.de/geotechnics/products/01sondiertechnik.htm

http://www.aei-euro.com/ingles/mecanica1.htm

Regards

 

[oldestguy]

Hi:

A friend of mine uses one made commercially, paterned after the paper by George Sowers 1959. For some reason his clients think it is magic and require it.

Uses a 15 # weight falling 20 " on e rod with 1.5" dia. cone with 45 degree tip.

Sold by Durham Geo-Enterprises Inc., Stone Mountain GA
1-800-837-0864

They furnish a chart relating to N value??????? More magic??

 

[dgillette]

oldestguy: "Uses a 15 # weight falling 20 " on e rod with 1.5" dia. cone with 45 degree tip."

With such small weight and fall, it sounds like it might be usable for probing at sites where you can't put a rig to use "dummy cone" (the polite name we used in reports when I worked in FL). However, it must be pretty limited in what strength/density it can test before it refuses. At what equivalent n does it refuse? I didn't find it on Durham's website, so might be discontinued?

Thanks,
DRG

 

[PSlem]

http://www.durhamgeo.com/testing/soils/field-testing-dynconepen.html

They also have STP399 with the original charts. It refuses about N=12

 

[dgillette]

Thanks PSlem. Never saw that particular penetrometer before. I shoulda had one of those when I was working in FL, although a lot of our problem materials there (organic muck and phosphate slime tailings) were so soft that we could use two 10' pieces of 1/2" allthread with a threaded sleeve coupler. Useful for finding sharp distinctions, but not well calibrated more precisely than Easy-One-Hand-Push, Difficult-Two-Hand-Push, or Refusal-With-100-Kg-Technician-Leaning-On-It. A denser or stiffer layer could mask softer material below it, but usually that wasn't a problem for identifying dense soil or very soft rock under slime.

 

[eric1037]

I know we have talked about this before, but you really have to calibrate the DCP for each site along-side your SPT hammer. If you do enough tests, it is possible to establish a correlation in your local geologic formations. I don't think it is appropriate to use the correlations developed in other geologic settings.

I actually plotted all of the established correlations that I could find for what I will term the Sowers DCP (a 15 # weight falling 20 " on e rod with 1.5" dia. cone with 45 degree tip). They were so radically different that I determined that our company needed to develop our own correlations that we felt comfortable with.

 

[72shortbox]

I have been working with the DCP developed by the army specified in NAVFAC MO 330 FM5-472. This has a smaller tip about 3/4". It was developed to measure CBR for airfield.
We bought it from Durham Geo a few years ago. Any one else have experience with this DCP good or bad

 

[eric1037]

basford:

There is a wealth of information the Army Corps DCP. The FHWA has done extensive research on it. My experience using it for estimating CBR for pavement design has been favorable.

 

[detate]

Dynamic probing (DP) is a Europeian standard EN ISO 22476-2 for soil testing there are 4 differeent methods. The light method is similar to the DCP familiar to in the USA - it delivers about the same energy per blow but it is driven differently. The test consists of a 10kg weight dropped 0.50 m to drive a 90° 35mm diameter cone with a 35mm mantle (straight section). The cone is driven 100mm then twisted with a torque wrench. The blows and torque are recorded for each interval. It is a continuous test with the next interval immdeiatly beneath the previous one.

I also need a correlation between the DP and SPT or Qu or Phi angle