Alex:
This State of Georgia DOT research project might also be of interest to you,
although it sounds like interpretation was problematic. This project was 5
years ago, so it might be worthwhile to see if there has been any follow up.
Nondestructive Assessment of Pile Tip Elevations
(RP 9406)
The objective of this research project is to develop a nondestructive test
procedure to assess pile tip elevations in the foundations of GDOT bridges.
For many of the 14,500 bridges on the state route system, pile tip
elevations are unknown because design and construction records no longer
exist. Thus the capacity of these piles cannot be easily determined,
particularly in the presence of scour. Although soil boring and other
intrusive tests are capable of determining pile tip elevations, Performing
these intrusive tests on a large number of bridges is extremely time
consuming and expensive.
Nondestructive testing is an effective alternative for assessing pile tip
elevations. In nondestructive tests, stress waves are generated by impacting
on a pile on an exposed surface. These stress waves then propagate downward
along the pile and are reflected at the tip. The arrival of the reflected
wave is monitored by sensors attached to the pile tip. Several
interpretation methods are available which determine the pile length from
these measurements.
The study was completed at the end of 1995, and a draft final report has
been completed. The analysis of the data collected from piles with known
lengths was more complicated than expected, and practical analysis
procedures have not been developed at present. For further information,
contact David Jared <mailto:[log in to unmask]> , (404) 363-7586 or
FAX (404) 363-7684.
Regards, Mike
-----Original Message-----
From: Bleakney, Michael (DOT/MDT)
Sent: Monday, June 26, 2000 9:36 AM
To: 'Alex Carson'; [log in to unmask]
Subject: RE: Pile length
I recommend you get a copy of : GT-16 <GT-16.PDF> (0.7 M) -
"Determination of Unknown Subsurface Bridge Foundations," (NCHRP 21-5
Interim Report Summary) at http://www.fhwa.dot.gov/bridge/geonote.htm
<http://www.fhwa.dot.gov/bridge/geonote.htm> for a start. This is a pdf
document you can get for free.
I would also recommend : Nondestructive Testing of Unknown
Subsurface Bridge Foundations - Results of NCHRP Project 21-5 available at
http://www.nationalacademies.org/trb/bookstore/ for under $20 US.
Good luck and regards.
Michael R. Bleakney, P. Eng.
Geotechnical Engineer
New Brunswick Department of Transportation
Design Branch
PO Box 6000
Fredericton, NB
E3B 5H1
Canada
Phone: (506)453-2674
Fax: (506)457-6714
E-mail: [log in to unmask] <mailto:[log in to unmask]>
-----Original Message-----
From: Alex Carson [SMTP:[log in to unmask]]
Sent: Sunday, June 25, 2000 3:53 PM
To: [log in to unmask]
Subject: Pile length
I am investigating the settlement of a viaduct with piled
foundations. The construction records indicate that the piles were driven
cast in-situ concrete. The ground condtions are peat with alluvial sands
overlying till and sandstone. At the abutments, where the worst settlement
has occurred (approx 200mm) the peat was excavated and replaced with
hydraulic sand fill.
The problem is how long are the piles because the pile
length on the construction records are significantly shorter than the design
lengths. The piles are raking. Access to the top of the piles is 5 to 6
metres below ground level.
Any ideas would be gratefully received on how to determine
the position of the toe of the piles or even just the depth.
Alex Carson
Principal Geotechnical Engineer
Babtie Shrewsbury
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