RCC Hydration Heat - Hadlock Dam Failure
RCC Hydration Heat - Hadlock Dam Failure
(OP)
In reference to the Hadlock Dam Failure (Northern NY) they poured RCC until January 17th. The slab was approx 3- 4 feet Thick x 40 feet across the dam and 125 feet long. A picture taken on January 27th showed part of the dam bare and about 70% having 1-3" of snow on it. There was no additional snow of any concequence prior to the resumption of construction on March 23rd when they resumed pouring RCC. The average temperature during that span was 20 degrees f. Overlaying the pre-failure structure with the Clough Harbour failure drawing the initial whirlpool center is nearly in line with the end of the RCC where it transitions to the existing earthen structure. From my calculations the RCC would have contracted approx 3/4" for every 10 degrees of cooling. From what I have read, RCC does not produce a significant amount of hydration heat and with a relatively thin slab and a large amount of surface area it is hard for me to believe that the tempeture of the slab did not drop. Once it contracted any compaction at the juncture with the earthen dam is gone creating a conduit across the entire width of the dam. The only other factor would be the frost in the ground adjacent to the slab at the end. Once they resumed pouring they added insulation over the cold concrete. The Clough Harbour report did not address this issue. I e-mailed the engineer at Clough Harbour questioning this and they acknowleged receipt. They have not commented on this or returned my follow up e-mail. Am I barking up the wrong tree.





RE: RCC Hydration Heat - Hadlock Dam Failure
RE: RCC Hydration Heat - Hadlock Dam Failure
RE: RCC Hydration Heat - Hadlock Dam Failure
However, you are right to look at the interface between the soil and concrete. Any shrinkage, lack of compaction or settlement along the interface would offer a preferred location for piping to occur. Standard practice (in this neck of the woods) would be to place a layer of filter material between the structure and the earth embankment. This is often called a filter diaphram and would prevent internal erosion and formation of a pipe along the structural interface.
RE: RCC Hydration Heat - Hadlock Dam Failure
The interface between embankment and RCC is definitely a suspect. The filter CVG mentions should be standard practice. Also, the drawings show vertical sides on the RCC walls, which is not the preferred way of doing things. Battered walls are easier to compact against (often by wheel rolling with a rubber-tire loader), and are more forgiving of small movements (such as slab shrinkage or consolidation settlement) because the soil is less prone to pulling away to leave a gap or an area with very low contact pressure against the wall. Those would be likely places for internal erosion to initiate.
I just skimmed the CH report and didn't notice any mention of the vertical walls, which doesn't necessarily mean they didn't mention it.
RE: RCC Hydration Heat - Hadlock Dam Failure
There is also one on the recent Taum Sauk failure in Missouri.
RE: RCC Hydration Heat - Hadlock Dam Failure
RE: RCC Hydration Heat - Hadlock Dam Failure
RE: RCC Hydration Heat - Hadlock Dam Failure
RE: RCC Hydration Heat - Hadlock Dam Failure
The fact that this is in reference to the Hadlock Dam is not relly impotant. This could be any slab of RCC.
I posed this concern to Clough Harbour in an e-mail several monthes ago and they said they would review it. I have sent them a follow up e-mail which they have not resonded to. I felt there report only looked at the "normal failure modes".
Is there a real posibility that the failure occurred from the shrinkage due to temperature opening up a crack across the entire dam. This slab traversed the entire dam. It extended from the main spillway 120 feet west where it ended against the existing embankment. Even if they compacted the soil between the RCC and the embankment as they built up the RCC, the slab was exposed all winter and any shrinkage could have negated the compaction or even opened up a crack at the transition. Before it warm up they resumed construction and covered that RCC with more RCC and fill insullating the wintered over material.
The CE Mag is just a rehash of everything that has bounced around locally.
RE: RCC Hydration Heat - Hadlock Dam Failure
http://www.pinebrookwater.com/