Looking at the many photos online of the Oroville Spillway collpase that has been in the news, there’s one major component of concrete that should be there, but is blatantly absent:
REBAR
Rebar (short for reinforcing bar), collectively known as reinforcing steel and reinforcement steel, is a steel bar or mesh of steel wires used as a tension device in reinforced concrete and reinforced masonry structures to strengthen and hold the concrete in tension. Rebar’s surface is often patterned to form a better bond with the concrete. Source
If there was REBAR in the spillway concrete, you’d see a mesh lattice of it left behind in the hole, or at least a few sticking out at odd angles. here are several photos, I don’t see any REBAR, do you?
ADDED: Here is a closeup view from our local newspaper, clearly no REBAR visible:
(Upon magnification of this image it appears there is some in the debris, so the question is now, was it enough, or was the problem due to some other factor)
Source: http://media.chicoer.com/2017/02/08/photos-oroville-dam-spillway-dwr/#7 (h/t to commenter TonyL)
If REBAR was present, we likely would not see such a dramatic collapse as it would have prevented water pressure cavitation from eroding more and more concrete. Concrete is a material that is very strong in compression, but relatively weak in tension. To compensate for this imbalance in concrete’s behavior, rebar is cast into it to carry the tensile loads. This means concrete pulls apart much easier than it is crushable, but with REBAR the tensile force required to pull the concrete apart is greatly increased.
One wonders if that lack of REBAR on the spillway was by design, accident, negligence, or some cost-cutting measure like the lack of life-boats and cheap steel on the Titanic. REBAR in concrete was invented in 1849. It seems incredible to me that it seems to be missing from this very important structure.
From AP:
OROVILLE, Calif. (AP) — State engineers on Thursday discovered new damage to the Oroville Dam spillway in Northern California, the tallest in the United States.
Earlier this week, chunks of concrete went flying off the emergency spillway, creating a 200-foot-long, 30-foot-deep hole.
Department of Water Resources spokesman Doug Carlson said officials will ramp up the outflow from the damaged site Thursday so officials can drain Lake Oroville.
Meanwhile, reservoir levels continued to climb behind the critical flood-control structure. Officials said it is at 90 percent of its capacity.
They said the dam is still safe and doesn’t threaten communities downstream.
“The integrity of the dam is not jeopardized in any way because the problem is with the spillway and not the dam,” said Eric See, a spokesman for the Department of Water Resources.
As a contingency, state officials are preparing to use the emergency spillway at the dam.
Crews have been clearing trees, rocks, and other debris from the hillside near the dam where water will flow.
Lake Oroville would naturally flow over this ungated concrete crest, into a mostly unlined emergency spillway if the reservoir reaches 901 feet elevation. This would be the first time the spillway has been used in the dam’s 48-year history although the reservoir came within 1 foot of flowing over in January 1997.
Absolutely off topic re “Global Warming” – but I did not start the discussion:
In some concrete reciepes, rebar is replaced by stainless steel fibres, typically 50 mm long and 1 mm diameter. Moderately popular for parking lots etc.
Steel quality in shipbuilding: the introduction of arc welding necessiated new steel composition – riveted ships could accept entirely different steels. More Liberty ships sunk due to metallurgical failures than number sunk by German warfare.
Absolutely ON topic as to the subject matter of this thread, please note.
For an actual case of a government project where some rebar was missing, look up the Montreal Olympic stadium which had some large chunks fall to the ground. It was built for the 1976 summer games. Quebec contractors are still well known for corruption and organized crime connections. Back then the politicians were indistinguishable from the crime bosses.
I would guess that no amount of REBAR would have prevented this, because AFAIK the problem here appears to be that water got underneath the concrete and washed out the soil between the concrete and the bedrock. I’d guess this was a process going on over a longer time.
What did the Bid Request say? Did it specify rebar and at what standard?
When we lived in Minnesota there was a big highway project to replace a ton of bridges. The problem was that the bid request did not specify salt resistant concrete in a snowbound state. The bridges were all built with standard concrete and just a few years later that all had to be rebuilt. More than double the money.
Living in FL, we frequently see shots of sink holes! This looks like a typical sink hole caused by water flow UNDER the spillway. Possibly an undetected underground spring that has increased volume due to all the rain CA has gotten this year. Or it might be caused by a leak in the dam below the spillway entrance! If this is the cause, rebar wouldn’t have stopped this collapse.
The sidewalls and the narrow inner skirt may be connected by rebar, as they are still intact, but because they are still intact, one cannot prove this. However, the sidewall/inner skirt combination does not seem to have interconnecting rebar to the “driveway” part of the spillway. Note the dark brown vertical lines going into the soil next to the edge of the skirt – very regular, man-made. No re-bar extending outward from the edge of the inner skirt into the failed “driveway” part of the spillway. Seems odd to me.
Probably off-topic, but what the heck – stainless steel rebar is now common in highway structures in the UK.
http://www.standardsforhighways.co.uk/ha/standards/dmrb/vol1/section3/ba5701.pdf
Oops.
“[Un]suitable for the general assembly of the public”
60 Million (US) high school stadium in Tejas exhibits serious cracking in concrete structure
THIS was in 2014 !!
http://cdec.water.ca.gov/cdecapp/resapp/getResGraphOiginal.action?resid=ORO&waterYears=1976&waterYears=1982&waterYears=2016&waterYears=1977
Let’s see another reservoir.
http://cdec.water.ca.gov/cdecapp/resapp/resDetailOrig.action?resid=SHA
Not sure I saw this in the thread to date, so –
“Birth of the Oroville dam”
Thank you, blank Jim! That was a treat to watch. Good to see one of California’s good governors there at the end, too. 🙂
Engineers are the BEST!
#(:))
Does anyone have a flood map if the emergency spillway is topped.
The predicted amount of rainfall in inches of water in California from 02/10/2017 to 02/11/2017.
https://www.ventusky.com/?p=37.8;-119.8;5&l=rain-ac&t=20170211/15&m=gem
Mosher above – Great links to nice photos.
It looks like cracks may have been visible in 2013.
Also interesting is that there appear to be PGE transmission towers crossing the emergency spillway.
http://fcdn.mtbr.com/attachments/california-norcal/1120603d1486695238-ot-oroville-reservoir-situation-16508579_1212016275513733_1512733581637597118_n.jpg
re: “Also interesting is that there appear to be PGE transmission towers crossing the emergency spillway.”
Cold this somehow in any way (even remotely!) be connected with the power generating station located at the Oroville dam?
Clearly, Climate Change caused the rebar to oxidize prematurely and completely vanish.
They opened up again last night.
Looks like the failure is increasing not only below and to the side but also uphill.
http://www.sacbee.com/news/state/california/water-and-drought/article131743014.html
Here is some additional information from Dr. David Petley’s blog. He’s got a nice writeup and photos that aren’t posted here:
http://blogs.agu.org/landslideblog/2017/02/10/oroville-dam-1/
As a contingency, state officials are preparing to use the emergency spillway at the dam.
Crews have been clearing trees, rocks, and other debris from the hillside near the dam where water will flow.
*****************************************
so theres an emergency spillway.
and its not maintained in a manner that allows its emergency use.
small wonder the main spillway failed…
The “emergency spillway” aka “the doomsday dam” is not an actual spillway. Its the designed hardened low spot in the dam where (in extremis) the water is supposed to overflow to prevent damage to the main part of this earth filled dam.
The spillway of Canyon Lake TX was also designed this way so during the 500 year flood 2002 eroded the spillway which blocked the river preventing operation of the floodgates. The erosion made an interesting feature about two miles long which is now a protected park.
Seems pretty clear that the substrate supporting the spillway was removed.
Next questions might be when, and more importantly how.
Lots of engineers sweating right about now.
and inspectors and contractors….
Lack of control joints caused concrete to crack. Reinforcement corroded. Saturated soil under cracks and venturi effect sucked fines up through cracks when the spillway was flowing. Foundation was undermined and caused surface failure.
It looks like Mosher is looking to bone up on some other fields than Climate services…;>)
Next up – Nick!
T-Man
I have examined the photo There is no rebar there was it by design ? I don’t know but there aint none there.
Mud Busters Local 904
email amd name in the box.
There is some rebar visible in the fifth picture in the piece of concrete lying on the big one. But the concrete is mucht too thin for this kind of construction. Also the points of breakage look strange. Like the concrete was poorly mixed, not enough of cement, not enough compaction, too dry, too cold, whatever.
But the
concreterebar is much too thin…Sorry
It is not possible to resolve rebar in the scale of the Oroville Dam spillway photos.