Item: THE TAP-O-METER: HOW HARD DO WE TAP AND SO WHAT?
-
-
Title: THE TAP-O-METER: HOW HARD DO WE TAP AND SO WHAT?
Proceedings: International Snow Science Workshop 2024, Tromsø, Norway
Authors:
- Håvard B. Toft [ The Norwegian Water Resources and Energy Directorate, Oslo, Norway ] [ Center for Avalanche Research and Education, UiT - The Arctic University of Norway, Tromsø, Norway ]
- Samuel V. Verplanck [ Department of Civil Engineering, Montana State University, Bozeman, MT, USA ]
- Markus Landrø [ The Norwegian Water Resources and Energy Directorate, Oslo, Norway ] [ Center for Avalanche Research and Education, UiT - The Arctic University of Norway, Tromsø, Norway ]
Date: 2024-09-23
Abstract: The hand-tap loading method is utilized in both Compression Tests (CTs) and Extended Column Test (ECTs). Discrepancy among the written standards of the United States, Switzerland, Norway, and Canada, as well as inherent subjectivity of the method’s implementation motivate our study’s objectives to characterize the impact force-time curves and quantify the variability between practitioners. We developed the “tap-o-meter”, an instrument consisting of shovel blade mounted to a load cell which records the applied force during a hand tap at a rate of 50 kHz. This sampling rate enables precise measurement of both peak force and loading rate, the two metrics chosen to characterize the applied loads. We collected data from 286 practitioners, including avalanche forecasters and mountain guides in Scandinavia, Central Europe, and North America to generate a data set of 8522 individual taps. For each loading step (wrist, elbow and shoulder), the inner quartile peak forces are distinctly different, as are the loading rates. However, there is significant overlap across the range of measurements, with instances of participants applying more force in wrist taps compared to the shoulder taps of others. This overlap challenges the reliability and reproducibility of ECT results, potentially leading to dangerous interpretations in avalanche decision-making, forecasting and risk assessments. The data collection process was paired with a short survey which included weight, height, gender, country of residency, and avalanche climate. The information in these explanatory variables did not explain the bulk of the variance. The only explanatory variable that is significantly correlated with tap force across all multivariate regression models is gender. Our results provide an answer to the question of “How hard do we tap?” but not necessarily “How hard should we tap?”. We believe these data and insights will enable discussion among the tests’ creators, the scientific community, and the practitioner community to update thresholds, guidelines, and test interpretation.
Object ID: ISSW2024_P11.5.pdf
Language of Article: English
Presenter(s): Håvard B. Toft
Keywords: stability tests, impact force, hand taps, tap-o-meter, standardization, decision-making
Page Number(s): 1539 - 1545
-