Item: Changes in Extended Column Test Results with Varying Depths
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Title: Changes in Extended Column Test Results with Varying Depths
Proceedings: International Snow Science Workshop 2016 Proceedings, Breckenridge, CO, USA
Authors:
- Ian Hoyer [ Colorado Avalanche Information Center, Boulder, CO, USA ]
- Ethan Greene [ Colorado Avalanche Information Center, Boulder, CO, USA ]
- Doug Chabot [ Gallatin National Forest Avalanche Center, Bozeman, MT, USA ]
- Karl W. Birkeland [ USDA Forest Service National Avalanche Center, Bozeman, MT, USA ]
Date: 2016-10-02
Abstract: Knowing the Extended Column Test's (ECT's) effectiveness at different slab thicknesses is critically important for practitioners. To better understand the limitations of the ECT, we used the SnowPilot dataset to investigate the utility of ECTs for providing an index of crack initiation and propagation on varying weak layer depths. The database currently contains 5013 ECTs conducted by 386, primarily professional, users worldwide between 2007 and 2016. The broad range of observers and snowpacks in the dataset allow us to examine variations in ECT results with changing weak layer depth across seasons and locations. We found 25% of ECTP (propagating ECT) results have weak layer depths of less than 30cm, 45% have depths between 30 and 70 cm, and 30% propagate on weak layers deeper than 70 cm. We also found an increasing ratio of ECTP to ECTN (non-propagating ECT) results as depth increased. The results make intuitive sense as fracture initiation takes more force and becomes more infrequent as slab depths increase, especially once depths exceed about 1.2 m. In addition, we used these same data to look at the repeatability of ECT results in individual snow pits. In the 582 pits where two ECTs were performed on the same weak layer, 86% have similar results (either two ECTPs or two ECTNs), showing a high degree of repeatability. Our results suggest the ECT can be effectively used over a fairly wide range of weak layer depths.
Object ID: ISSW16_P4.29.pdf
Language of Article: English
Presenter(s):
Keywords: Extended Column Test, Snowpack Test, Propagation
Page Number(s): 1302-1306
Subjects: Snowpack Test Propagation Extended Column Test
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