| 1. |
- Lundberg, Angela
(författare)
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Laboratory calibration of TDR-probes for snow wetness measurements
- 1997
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Ingår i: Cold Regions Science and Technology. - 0165-232X .- 1872-7441. ; 25:3, s. 197-205
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Tidskriftsartikel (refereegranskat)abstract
- In situ registration of snow liquid water content for avalanche protection and snow-melt prognosis is much needed. The Time Domain Reflectometry (TDR) method is a possible method to meet this need. Laboratory comparison of the TDR-method with the dilution method shows that the TDR-method has the potential to register variations in snow liquid water content down to 1-2 vol.%. It should be possible to achieve continuous registration of snow-pack wetness with a spatial resolution down to approximately 5 cm with several sets of TDR-probes (mounted with 3 cm vertical and 5 cm horizontal distance) combined with a multiplexer and a storage unit. For application when changes in snow density are great (as with newly fallen snow) the method has to be combined with separate density determinations. The dielectric constant of night-time refrozen snow can be used for density determination.
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| 2. |
- Nordell, Bo, et al.
(författare)
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Method for continuous measurement of ice cover thickness
- 1995
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Ingår i: Cold Regions Science and Technology. - 0165-232X .- 1872-7441. ; 23:4, s. 389-391
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Tidskriftsartikel (refereegranskat)abstract
- The objective of this study was to evaluate a method for continuous measurement of ice cover thickness. The measuring device consists of a water-filled bucket, floating with its brim at the water surface. A pipe is vertically mounted at the centre of the bucket and capped with an oil-filled balloon. The volume expansion of the formed ice results in a corresponding oil flow, from the balloon at the bottom of the bucket through the pipe into an expansion bucket above ground. By measuring the volume expansion continuously, the ice thickness can be determined at any time. The performance of preliminary laboratory tests confirmed the feasibility of the method.
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| 3. |
- Viklander, Peter
(författare)
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Laboratory study of stone heave in till exposed to freezing and thawing
- 1998
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Ingår i: Cold Regions Science and Technology. - 0165-232X .- 1872-7441. ; 27:2, s. 141-152
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Tidskriftsartikel (refereegranskat)abstract
- Cyclic freezing and thawing of soils affect the structure and might, under certain conditions, cause stones and particles to move and relocate. The movement of stones will influence the soil structure and create weak and loose parts with increased permeability. This phenomenon has been known for a long time, but the knowledge regarding the magnitude of stone heave and soil conditions necessary for heave to take place has been lacking. Therefore, laboratory tests were carried out. Fine-grained till (moraine) was compacted to different void ratios and then saturated in a rigid wall permeameter which was exposed to one-dimensional freezing and thawing in a closed water system. The movements of an embedded stone were measured by an X-ray technique. Unfrozen samples, as well as samples frozen and thawed, were X-rayed and the stone movements were quantified after 1, 2, 4, and 10 cycles of freezing and thawing. The results show that stone movements (vertical and horizontal) take place due to freeze/thaw. The void ratio (the ratio of the volume of void space to the volume of solid substance in the sample) was found to be a key parameter for whether upward or downward stone movements took place. The downward movement occurred when the soil had a high void ratio, and the upward when the void ratio was small. In the loose soil, the stone first moved downwards and then, when the soil became denser due to freeze/thaw, it changed direction and heaved. In the loose soil, significant movements in the horizontal direction as well as rotation of the stone were also found.
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| 4. |
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