The "Extended Column Test"

The promotion of this "test" as something useful in decision making in the field has bothered me for quite a while. I will have to find time to write more about it again later, but here is the short version of my concerns, as well as a suggestion for what to ask anyone promoting this.


First, what does it supposedly tell us and is that useful? Well, it's not clear that it tells us whether weak layers exist or how strong they are. Rutschblock and compression tests are still best for that. The Extended Column Test (ECT) supposedly tells us, given a weak layer, whether it is likely to propagate a failure or not. This presumes the existence of a weak layer where a failure can be initiated. One person wrote that they had tried this test along with traditional ones and this one would have made them less conservative in every case. Is this a surprise? You won't rule out slopes with this that wouldn't be ruled out with established tests. All you will do is justify a slope as safe, despite a weakness, based on its supposedly poor potential to propagate a failure.

Do you really want to identify a weakness then ski a slope anyway because you don't think a failure will propagate? I don't. Especially if the test is less than perfect, and all of them are.

This test was first presented at the ISSW in the fall of 2006. Also presented was a Prototype Fracture Propagation Test by Canadian researchers Gauthier and Jamieson. The ECT had been done a few hundred times, in two general locations. There were not well planned research plots to collect meaningful and controlled data. Nothing about the test had ever been published in a peer reviewed journal. I'm not sure anything has been yet. On the other hand the Canadian prototype test had been very well studied. Data had been collected over several seasons from well-planned study plots. All kinds of variations in the test configuration were studied and compared statistically. And this had resulted in numerous publications in peer reviewed technical journals.

Now, if you were inclined to attempt to measure fracture propagation propensity which test would you want to rely on?

I believe there are two reasons the ECT has been hyped in the US without much reference to the Canadian test. The first is that the Canadian test was never presented as a final test ready to use in the field. It was always preceded with the word "Prototype". The researchers working on this would not have wanted it promoted for general use at that time. In the December 2007 issue of Avalanche Review it is presented to the public in simple terms as a true test, for the first time I believe. The status of the ECT was not qualified in this manner very clearly.

The second reason is that presentations and paper on the Canadian test, until recently, were presentations on research. Involving data collection methods and plans, statistical analysis of results, and comparisons to complicated theoretical calculations on fracture mechanics. There is not much of a community of true scientists and engineers in snow science in the US. In fact, science education in the US has deteriorated in recent years. So people attending the ISSW aren't going to pay any attention to anything that technical. They are going to pay attention to something they think they can walk out the door and use. Whether they clearly understand its basis or not.

So if somebody promotes the ECT, or implies in their teaching or writing that it is important or useful, I suggest asking them about it. Ask if they've compared it to the Canadian test and if they are familiar with that work. (Most likely they will be vaguely aware of it but not very familiar with it.) Ask them why they feel the ECT can be reliably interpreted - on what basis? And ask them what they think about the number of studies and details analyzed for each test. If they can't answer these questions, or engage in an intelligent and informed technical discussion, they should not be promoting the test.

The ECT test may prove to be a viable tool. That will require significant further study. Well planned study, with results that can be analyzed with statistical significance, and with fracture mechanics theory to help explain the mechanics of the test. Until then it's simply an interesting idea.

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