[u]Does anyone know of any studies
[u]Does anyone know of any studies
(OP)
Does anyone know of any studies regarding the validity of the ENR pile driving formaula, Safe Load = (2WH)/(s+1) and what Factor of Safety was used? I took the formula from "Foundations of Bridges and Buildings", 1914 edition, by Henry S. Jacoby.
Here's what's going on: I got sucked into a bridge rehab project - of course no job number, but it's Lent and alms giving is good - a steel viaduct (circa 1920's) with a non-operational double leaf bascule main span, supported on timber piles approximately 70' long. The leafs (or is it leaves?) were locked in the 50's; the machinery was removed, and the pits have been flooded since.
The owner wants to fill the pits with lightweight concrete. The PM (not a bridge guy) and his design team (including geotechs) are opposed since they don't know the pile capacity. They assume it's 20, maybe 30 T (which is not unreasonable for a timber pile) and believe the piles are only loaded to 20 T or maybe 26 T. (This has been going on for 3 years now; that's why I fustrated.)
In the original drawings I found a note stating capacity is achieded with a 3000 # hammer, dropped 15 feet; 1/2" displacement for the last five blows. If I use the ENR formula and the plan data, I arrive at 30 T capacity; I would assume the ultimate would have be at least twice this number. The soil is a thick organic layer on top of sand.
Thanks
Here's what's going on: I got sucked into a bridge rehab project - of course no job number, but it's Lent and alms giving is good - a steel viaduct (circa 1920's) with a non-operational double leaf bascule main span, supported on timber piles approximately 70' long. The leafs (or is it leaves?) were locked in the 50's; the machinery was removed, and the pits have been flooded since.
The owner wants to fill the pits with lightweight concrete. The PM (not a bridge guy) and his design team (including geotechs) are opposed since they don't know the pile capacity. They assume it's 20, maybe 30 T (which is not unreasonable for a timber pile) and believe the piles are only loaded to 20 T or maybe 26 T. (This has been going on for 3 years now; that's why I fustrated.)
In the original drawings I found a note stating capacity is achieded with a 3000 # hammer, dropped 15 feet; 1/2" displacement for the last five blows. If I use the ENR formula and the plan data, I arrive at 30 T capacity; I would assume the ultimate would have be at least twice this number. The soil is a thick organic layer on top of sand.
Thanks





RE: [u]Does anyone know of any studies
RE: [u]Does anyone know of any studies
The author calls (2WH)/(s+1) the ENR formula. I better look in some other ancient textbooks for a comparison.
RE: [u]Does anyone know of any studies
Using the Gates formula for your application and information:
Ru=27[(Eh)(eh)(1-log s)]^0.5
Eh=hammer energy in ft-kips
Ru=ultimate bearing capacity in kips
s=set in inches
eh=hammer efficiency (0.75 for drop hammers, 0.85 all others)
Applying the recommended FS for this formula of 3.0, it yields a capacity of......30 tons!
RE: [u]Does anyone know of any studies
Would filling with such material be a lower load than from the water currently flooding the pits? (plus you mention that machinery loads have been removed)
RE: [u]Does anyone know of any studies
RE: [u]Does anyone know of any studies
RE: [u]Does anyone know of any studies
I was reading up on things and noted that a FS of 3 to 6 was generally applied to the ENR formula. I have the 1984 ed. of Das; he recommends 4 to 6 for the modified ENR.
geobdg - have you used this particular material? I don't see a structural problem with filling the pits with lightweight concrete. To me, it's a construction problem - placing 2000+ CY of concrete from a crowded city street.
What annoys me is that a group of people have been working on this for years and they can't make a decision. All they keep saying is the pit can't be filled; and the client keeps saying prove it. Whatever, I offer in terms of meeting the client's expectations will be useless.
RE: [u]Does anyone know of any studies
The fill was a cellular concrete with pearlite aggregate...a hybrid of two roofing material lightweight insulating concrete fills. It worked fine.
I have also used cellular fill for pavement over a swampy area. That worked as well.
I didn't follow the link, but this is likely what geobdg is referencing or similar.
RE: [u]Does anyone know of any studies
There are also various other lightweight materials (such as flowable fill with foaming agent). Of course with the material used you'd need to consider whether it would become saturated and increase the unit wt.
RE: [u]Does anyone know of any studies
RE: [u]Does anyone know of any studies
RE: [u]Does anyone know of any studies
RE: [u]Does anyone know of any studies
RE: [u]Does anyone know of any studies
You'd probably be better off starting from scratch with a theoretical design capacity based on CPT data than you would be relying on the ENR formula.