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tuolumne_tradster
Trad climber
Leading Edge of North American Plate
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Feb 13, 2017 - 10:58pm PT
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I'm trying to draw attention to the underlying bedrock geology and all you guys want to talk about is rebar ;-(
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Reilly
Mountain climber
The Other Monrovia- CA
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Feb 13, 2017 - 11:06pm PT
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That rebar job is a joke. If it was designed right and done right it
would not have failed. It looks like it is at least a foot apart, not
heavy enough, and too close to the surface. Besides, for that type of
job there should be a lower and an upper cage the way runways are done.
The taxpayers take it in the shorts again, as usual. And what about the
cold joints and the spalling? It's a complete fiasco.
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TomCochrane
Trad climber
Cascade Mountains and Monterey Bay
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Feb 13, 2017 - 11:22pm PT
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uncoated steel rebar only retains its strength when sealed in concrete
cold joints, stress cracks, and spalling allow moisture and air to penetrate and cause corrosion
the corrosion products expand 5-10x inside the concrete and create further spalling
this process accelerates as structural integrity degrades
there are procedures for repairing such damage before it gets away from you
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tuolumne_tradster
Trad climber
Leading Edge of North American Plate
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Feb 13, 2017 - 11:40pm PT
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Geology Professor Jeff Mount from UC Davis, who was interviewed on NPR this morning RE
the Oroville dam, gave this testimony before the House Committee on the
Implementation of the Endangered Species Act in 1997. Jeff's testimony,
which had very little to do with the ESA, focused on breaking the Cycle of
Serial Engineering of our rivers....
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healyje
Trad climber
Portland, Oregon
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Feb 14, 2017 - 12:18am PT
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They probably did to some degree, but it doesn't look like they bothered with much compacting under the spillway.
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Delhi Dog
climber
Good Question...
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Feb 14, 2017 - 02:05am PT
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Reminds me a bit of the Glen Canyon fiasco back in 83.
Besides a lot of other mistakes the "cavitation" was determined to be the factor in the 'spillway' getting trashed and a major contributor to them almost loosing the dam (though they wouldn't admit that).
I see similar results from the Oroville spillway with that hole dug into and through the cement.
Oh and I'm thinking there's gonna be a lot of gold accessible in the upcoming months:-)
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mcreel
climber
Barcelona
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Feb 14, 2017 - 05:41am PT
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Whoa, Delhi, that's a good point!
I hope that the weather allows them to get the sh#t back together. The book "The Emerald Mile" that Donini mentioned up thread is good background for all of this.
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clinker
Trad climber
Santa Cruz, California
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Feb 14, 2017 - 06:24am PT
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[quote]The compressive strength of concrete is tremendous. Incredible force is required to crush concrete. However, concrete has relatively weak tensile strength. Far less force is required to crack concrete by bending or twisting it than is required to crush concrete. To increase the tensile strength of concrete, reinforcing bar rebar is used to increase the tensile strength of concrete.
A variety of rebar lengths and diameters are available, but there are only six common types of rebar: European (a carbon, manganese, silicon, etc. alloy); carbon steel (basic black rebar); galvanized; epoxy coated; glass-fiber-reinforced-polymer (GFRP); and stainless steel. The different types of rebar each unique strengths and weaknesses.
Types of Rebar
European Rebar The strength of European rebar is its cost. Made principally of manganese, European rebar is the least resistant type of rebar with respect to bending. While easy to work with, it is generally not recommended for use in areas that experience earthquakes nor for projects that require substantial structural integrity from its rebar.
Carbon Steel Rebar The most common rebar, black bar is used on every type and scale of project with few exceptions. The biggest weakness of black rebar is that it corrodes. When rebar corrodes, it expands cracking and breaking the concrete around it. For situations in which the rebar might be exposed to humidity or water saturation, there are better options than black rebar. However, with respect to is value/tensile strength ratio, black rebar is the best rebar available.
Epoxy-Coated Rebar Epoxy-coated rebar is black rebar with an epoxy coat. It has the same textile strength, but is 70 to 1,700 times more resistant to corrosion. However, the epoxy coating is incredibly delicate. The greater the damage to the coating, the less resistant to corrosion.
Galvanized Rebar Galvanized rebar is only forty times more resistant to corrosion than black rebar, but it is more difficult to damage the coating of galvanized rebar. In that respect, it has more value than epoxy-coated rebar. However, it is about 40% more expensive than epoxy-coated rebar.
Glass-Fiber-Reinforced-Polymer (GFRP) GFRP is a composite much like carbon fiber. As a result, field bends are not permitted when using GFRP. However, it will not corrode, period. In that respect, GFRP is an unparalleled concrete reinforcement bar. While it costs ten times as much as epoxy coated rebar per pound, it is extremely light, so the cost is only about double when considering talking linear feet.
Stainless Steel Rebar Stainless steel rebar is the most expensive reinforcing bar available, about eight times the price of epoxy-coated rebar. It is also the best rebar available for most projects. However, using stainless steel in all but the most unique of circumstances is often overkill. But, for those who have a reason to use it, stainless steel rebar 1,500 times more resistant to corrosion than black bar; it is more resistant to damage than any of the other corrosive-resistant or corrosive-proof types or rebar; and it can be bent in the field.
 See more at: http://www.bnproducts.com/blog/what-are-the-different-types-of-rebar-and-why-do-types-matter/#sthash.EpCA6AQV.dpuf[/quote]
Define "often overkill"
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fear
Ice climber
hartford, ct
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Feb 14, 2017 - 06:39am PT
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I'm trying to draw attention to the underlying bedrock geology and all you guys want to talk about is rebar ;-(
Nobody gives a schist.
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hooblie
climber
from out where the anecdotes roam
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Feb 14, 2017 - 07:04am PT
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i like rocks. up to two syllables is best
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fear
Ice climber
hartford, ct
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Feb 14, 2017 - 07:12am PT
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Just wait until the dollar implodes.
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rick sumner
Trad climber
reno, nevada/ wasilla alaska
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Feb 14, 2017 - 08:12am PT
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The whole thing is a slow motion train wreck, at least 12 years in the making.Now they make these confused half measures of emergency repair. Good for the less discerning glued to the cameras, but a charade. They'd be better off with divers and mini subs unsealing the diversion tunnels.
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pb
Sport climber
Sonora Ca
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Feb 14, 2017 - 08:16am PT
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any rebar in the whitehouse?
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stunewberry
Trad climber
Spokane, WA
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Feb 14, 2017 - 08:25am PT
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Looks like they're dumping them into a drain by the parking lot that ran a lot more than it was designed for. So I don't think that's staging.
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tuolumne_tradster
Trad climber
Leading Edge of North American Plate
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Feb 14, 2017 - 09:40am PT
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So T Tradster what is that rock unit at the dam? Motherlode Jurassic 'slate'? Or perhaps serpentinite?
From what I can tell it is green schist facies metamorphic volcanic rocks. The geologic unit on the geologic map at the dam is "mv" that is identified in the Legend as volcanic rocks of the Jurassic Smartville Ophiolite Complex. So this is not "Serpentine" but mainly schist derived from the burial and metamorphosis of volcanic rocks that were originally deposited in an island arc complex along the N American margin during the Jurassic (150-200 MYA) in a tectonic setting similar to modern Japan.
This is what an idealized ophiolite sequence looks like...
So the rocks at the dam site are roughly equivalent to the "Pillow lavas" in the above sequence which would be tholeiite basalts that were deposited on the ocean floor possibly in a back arc spreading center within the island arc complex. When the upper mantle melts (e.g., at an oceanic spreading ridge) it produces tholeiitic basalt.
Genesis of the Smartville arc-ophiolite, Sierra Nevada foothills, California
American Journal of Science Vol 280-A, 1980, p 329-344.
Abstract
Rare earth element analyses of metavolcanic rocks from the Smartville, Calif. ophiolite divide the uniform suite of pillowed and massive lavas into the lower part consisting of massive, brecciated tholeiites, an intrusive dike-sill complex, and part of a plutonic suite. The tholeiites are light REE depleted with a (Ce)N range of 6.5 to 26.0 and (Yb)N of 6.0 to 30.0; it is suggested that the tholeiites were produced by partial melting of a LREE depleted source similar to MORB. The upper part of the volcanic pile is comprised of basaltic-andesitic flows and interbedded coarse to fine volcanic sediments; these 'calc-alkaline' rocks are light REE enriched with the (Ce)N range of 17.0-28.0 and (Yb)N of 8.0 to 12.0. Finally, petrographic investigations of volcanic sediments and sulfide ore deposits in the lava show that the ophiolite formed near a group of active submarine and subareal volcanoes.
In a tectonically active region like California, "bedrock" can be a messy thing ;-)
The real question is the structural integrity of these highly fractured and sheared meta volcanic rocks in the presence of dynamic loading and unloading within the reservoir due to weather events and dam operation and the ability of these rocks to withstand the erosive capacity of the high flow rates ~100K cfs that are being released from the dam in order to lower the water level in anticipation of storms due to arrive later this week.
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Branscomb
Trad climber
Lander, WY
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Feb 14, 2017 - 09:59am PT
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I admire the Butte Cnty Sherriff for being a stand-up guy. Just the day before all the 'experts' were saying there was no problem, no worries...blah blah blah.
Big call to evacuate all those thousands of people when the 'experts' are saying no worries. He showed good courage and did the right thing. If that thing had cut loose, there would have been thousands of people killed.
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skcreidc
Social climber
SD, CA
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Feb 14, 2017 - 10:19am PT
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Dang, ophiolite sequences are really cool! But the dam is built on green schist? They are probably fuked. Let the water out. Now.
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John M
climber
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Feb 14, 2017 - 11:05am PT
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I wonder why they are using helicopters to fill those holes near the parking area? Why not use trucks and tractors? There must be a road to that section from the other side. Then they would have the helicopters for below the spillway.
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