Journal of the Japanese Society of Snow and Ice

Structure of Perennial Snow Patches in Mt. Daisetsu Area, Hokkaido

Masuyoshi MATSUDA

1976 Volume 38 Issue 3 Pages 115-126
Published: September 30, 1976
Released on J-STAGE: September 04, 2009

DOIhttps://doi.org/10.5331/seppyo.38.3_115

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A number of perennial snow patches of the order of 100 m in long dimension are found in some valleys in Mt. Daisetsu area at the ablation season. Three snow patches of different sizes, located near the uppermost edge of the wide slope on the east side of the plateau “Takanegahara” (43.6°N, 124.9°E, altitude; 1700-1750 m), were studied during the ablation season of 1972 in connection with thier growing processes and from view point of structural geology. They are 200 m, 100 m and 50 m in length. Stratification, cross-bedding, fault, crevasse, summer surface, bergschrund, water channel and grain size with depth were investigated from the successive observations of thier surfaces and core samples obtained by drillings.
It was found through the observations that these three snow patches were formed by the successive advancement of a big cornice extended from the edge of the plateau. The extension is primarily governed by the bed rock topography : only a slight difference in its topography makes a big difference in the size of a snow patch in the region under similar meteorological conditions.
Three types of cracks were observed. Similar cracks like crevasse in a valley glacier were found in the largest snow patch. Most of melt water was observed soaking on to the summer surface of the previous year, and water channels were also observed in the larger two snow patches. The schistosity is not formed, and the stratification survives until it disappears at the bottom by the bottom melting several years after the deposition. It was confirmed by these observations that the more structural elements. are formed in the larger perennial snow patch.

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A Simulation Computation of Twist of De-Snowing Electric Wires due to Snow Accretion

KAZUO GOTO

1976 Volume 38 Issue 3 Pages 127-137
Published: September 30, 1976
Released on J-STAGE: September 04, 2009

DOIhttps://doi.org/10.5331/seppyo.38.3_127

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As the measures to improve the de-snowing effects of the electric wires on long spans, anti-torsion weights or anti-torsion spacers were installed in the middle of the spans to prevent the wires from twisting.The de-snowing effects were decreased on long spans, owing to the twist of the wires in the middle of the spans due to the moment of the accreted snow.
A computer aided simulation on the growth of snow accretion is presented to investigate whether accreted snow falls off during accretion or developes to the cylindrical deposit. For this computation a wire span is divided into several parts for which the change of twisted angle due to snow load is estimated. The relation between the twisted angle and the amount of snow accreted on each wire segement is calculated by the Newton-Raphson's method.
Two computation examples are given for actual de-snowing electric wires; 300 m long ACSR (aluminuium conductor steel reinforced) wire with 16 mm in diameter, and 270 m long ACSR wire, 18 mm in diameter, attached with two anti-torsion weights of 0.8 kg-m. Computed twist angle in the center segment of the former wire reaches to 360°, whil the latter gives 120°.

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An Improved Snow-Disaster Index Considering the Effect of Snow Removal

Tetsuro NAKATAO

1976 Volume 38 Issue 3 Pages 138-142
Published: September 30, 1976
Released on J-STAGE: January 22, 2010

DOIhttps://doi.org/10.5331/seppyo.38.3_138

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In the previous paper (Nakatao, 1968) three snow-disaster indices were introduced : (i) air temperature index P_θ, (ii) precipitation index P_W, and (iii) snowcover depth index P_H in terms of the average air temperature and monthly precipitation. The maximum disaster index Q was given by Q=Max (P_W, P_H).
Considering the economical requirement for snow-removal, an improved index T_{α, β} was introduced; T_{α, β}= (1-β+βkP_θ) ·Max (P_W, αP_H), where k= 0.63 is used for the practical use. The variation of T_{α, β} depending on two constants α and β was numerically estimated. The ratio of T_{α, β'}s at warm and snowy Hokuriku districts with respect to the value of unity at Hokkaido is 1.70.85 and the logarithmic mean of 1.2 when α=β=0.6 can be used for practical purpose.

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