A constant-speed penetrometer for high-resolution snow stratigraphy

Abstract

A new constant-speed penetrometer for field and laboratory measurements has been developed. The initially independent work of SFISAR and CRREL has been brought together, and a portable field device is now in an advanced stage of testing.The new penetrometer has high rigidity and a high-resolution large dynamic range force sensor. It uses a much smaller sensing head (5 mm ) than previous designs and has a constant.-speed drive. ''''ith th~s construction, the penetration rrsistance of ~'ery fine layers and th~ mf1uenc~ of the bond~ng strength between snow grains can be more accurately determmed than tS possible With the rammsonde or Pandalp. Artificial foam layers as thin as 2 mm and thin layers in snow have been detected by the penetrometer. Thin snow layers detecte? from penetration~resistance profiles have been correlated to finr layering as determmed from plane-sectIOn mlcrophotographs of samples taken adjacent to the profile. The instrument's measurements are highly repeatable and the lack of subjective decisions when operating the penetrometer makes the penetration resistance a quantitative measure of snow stratigraphy.

Nordic Snow Radar Experiment

“…The objective of the IOPs was to complement the collected time series of basic observations, in particular by employing advanced methods for characterization of snow microstructure. The measurements consisted of -SSA analyses using near-infrared (NIR) photography (Matzl et al, 2006), -snow micropenetrometry using the Snow MicroPen, (SMP; Schneebeli et al, 1998;Proksch et al, 2015a),…”

Estimating the effective elastic modulus and specific fracture energy of snowpack layers from field experiments

“…Sigrist and Schweizer (2007) were the first to estimate w f with field experiments and finite element (FE) modeling. Their method requires a Propagation Saw Test (PST;van Herwijnen and Jamieson, 2005;Sigrist and Schweizer, 2007;Gauthier and Jamieson, 2008) to determine the critical cut length r c and a snow micro-penetrometer measurement (SMP; Schneebeli and Johnson, 1998) to estimate the effective elastic modulus E of the slab. While Sigrist and Schweizer (2007) reported a mean fracture energy of 0.07 J m −2 , more recent results using the same methodology on eight different weak layers indicate substantially larger values, typically around 1 J m -2 (Schweizer and others, 2011).…”

Microstructure-based modeling of snow mechanics: a discrete element approach

“…In particular, investigating shear loading can be useful in the context of slope stability and avalanche release. Another promising prospect would consist in numerically reproducing the penetration of an indenter in the snow microstructure, with the objective of better understanding the signals delivered by micro-penetrometers, which are routinely used for snow characterization (Schneebeli and Johnson, 1998). Lastly, directly conducting mechanical experiments in the µCT (Wang and Baker, 2013;Schleef et al, 2014) would also be useful to evaluate the model and possibly reduce the uncertainties on the microscopic contact parameters.…”

“…This type of deformation is involved in the release of slab avalanches (Schweizer et al, 2003), in the characterization of a snow profile with an indenter (Bader and Niggli, 1939;Schneebeli and Johnson, 1998), or when a vehicle wheel comes in contact with snow on the ground (Yong and Fukue, 1977). To model this specific deformation regime, we propose to describe snow as a granular material, i.e., to simplify the microstructure into a set of rigid grains interacting only through their contacts.…”