雪氷チーム

Snow and Ice Research Team

北海道における雪崩予防柵の設計雪圧に関する研究
A Study on Design Snow Pressure for Avalanche Protection Fences in Hokkaido
我が国の雪崩予防柵の設計は50年以上前に制定されたスイスの示方書に基づいています。本州では雪圧の設計において、雪質に対応し、北海道と異なるグライド係数を用いています。北海道においても、近年の冬期温暖化の影響により雪質の変化が懸念されます。そこで、雪圧計測を行い、雪崩予防柵の設計手法を再検討しました。
The design of avalanche protection fences in Japan is based on specifications established in Switzerland more than 50 years ago. In Honshu, a glide factor forsnow pressure design that is different from the one for Hokkaido is used, in accordance with the different snow quality there. In Hokkaido, there have been
concerns about changing snow conditions as a result of the higher winter temperatures in recent years. To address such concerns, the design method for avalanche
protection fences was re-examined based on snow pressure measurements.

研究の背景■グライド係数 Glide factors

Background of the study

Hokkaido

Conditions of the ground surface(including vegetation)

我が国の雪崩予防柵設計手法は1961年に制定されたスイスの示方書に基づいている。
しかし、本州の湿雪には対応できず、現地で雪圧の観測を行い、グライド係数の割増を行った。北海道においても、雪質の変化に伴い、設計の見直しが懸念される。

Ⅱ・れき(φ30cm以下)の斜面
・丈1m以上のかん木地
・50cm以上の凹凸地面

II ・Slope with gravel (≦Φ30cm)

Ⅲ・小さいかん木地・50cm以下の凹凸地面
・草地

III・Short shrubbery

Ⅳ・平滑岩盤・葉の長い草地
・湿地

IV・Smooth bedrock

Honshu

北向き斜面

南向き斜面
(東西を含む)

北向き斜面

南向き斜面
(東西を含む)

1.2

1.3

1.8

2.0

1.6

1.8

2.4

2.7

2.0

2.4

3.0

3.6

2.6

3.2

3.9

4.8

Ⅰ・玉石(φ30cm以上)の斜面 I ・Slope with cobblestones (≧Φ30cm)
・Rugged surface with large rocks
・大岩の凹凸面The design of avalanche protection fences in Japan is based on
specifications established in Switzerland in 1961. However, the Swiss
design was unsuitable for the wet snow conditions of Honshu. The
Swiss glide factor was increased based on onsite measurements ofsnow pressure. In Hokkaido, where the snow quality has beenchanging, review of the design for avalanche protection fences has been
considered.

本州

北海道

地表の状態(植生等)

・Shrub of 1m in height・Rugged ground with 50cm in height difference・Rugged ground with less than 50cm in height difference・Grassland

・Grassland with long grass
・WetlandSouth-facing slope(including East- and West-facing slopes)

North-facing slope■雪崩予防柵に作用する雪圧の設計式 The design formula for the snow pressure that acts on an avalanche protection fence12
S = 2 γS H S KN

観測方法

・ys:積雪の単位体積重量
・Hs：積雪深・Ｋ：クリープ係数
・Ｎ：グライド係数・γs: unit weight of snowpack

・Ｋ: creep factor

・Hs: snow depth

・N: glide factor

Measurement method
雪圧の観測は国道230号中山峠と、国道275号朱鞠内で行いました。
雪崩予防柵を支えるワイヤーに引張型荷重計を設置して雪圧を観測します。過去の雪圧と、現在の雪圧を比較することで、雪質の変化に対応した新しい設計手法の提案を目指します。

Snow pressure was measured at Nakayama Pass on National Highway 230 and in the Shumarinai District on
National Highway 275. These measurements were made by installing tensile load meters on wires
supporting avalanche protection fences. By comparing previous measurements to the new measurements, we
aim at proposing a new design for avalanche protection fences that responds to the changes in snow quality.

引張型荷重計クリープ：

e

積雪が重力により時間と共に塑性変形する際の雪圧
幌加内町朱鞠内The Shumarinai District of
Horokanai TownsS

雪積

Creep: snow pressure during plastic
deformation of the snowpack causedby gravity

Tensile load meter面w
noacurf

グライド：

斜面積雪と地面との境界で滑る現象により発生する斜面雪圧。グライドは斜面積雪と地面との境界で発生するが、その雪圧は積雪内で均等に与えられる。

札幌市中山峠

Nakayama Pass in Sapporo City

雪崩予防柵

▲雪圧計測箇所図▲雪圧計測箇所（中山峠)

Snow pressure measurement
locations

Avalanche
protection fence▲雪圧観測方法

Snow pressure measurement location(Nakayama Pass)

雪崩予防柵に作用する雪圧の概念
The concept of snow pressure acting on
an avalanche protection fence

Glide: snow pressure on the slope that isgenerated by the snowpack sliding on the slope
along the boundary between the snowpack andthe ground. The glide is generated at theboundary between the snowpack on the slope
and the ground, and the snow pressure is
distributed equally to all parts of the snowpack.

Measurement method used in
the snow pressure observation

観測結果

Observation results
観測期間中に設計雪圧を上回ることはなく、現時点においては、設計手法を見直す必要性は低いものと考えます。
ただ、観測雪圧が積雪深に対応した計算雪圧を上回る例が融雪期に多く見られました。今後も経過を観察するために、雪圧の観測を継続する必要性は高いものと考えます。

50

18.5kN/mSnow pressure

設計雪圧

Design snow pressure: 18.5kN/m

10012/1
Dec. 1

1/1
Jan. 1

2/1
Feb. 1

3/1
Mar. 14030

H24(2012)

Sapporo side of Nakayama Pass

設計雪圧

H25(2013)

40.7kN/m

Design snow pressure: 40.7kN/m

20
100
12/1
Dec. 1

4/1
Apr. 1

日付

1/1
Jan. 1

2/1
Feb. 1

3/1
Mar. 1

4/1
Apr. 1

日付
Date

Date

▲雪圧の時系列変化(朱鞠内柵高2.0m)▲雪圧の時系列変化(中山峠柵高3.5m)

Time-series of snow pressure (Shumarinai snow fence: 2.0m high)

安全・快適Time-series of snow pressure (Nakayama Pass snow fence: 3.5m high)

北の道

Safe, pleasant driving on Northern Roads

計算雪圧

H26(2014)
Snow pressure acting on the fence

Shumarinai

中山峠札幌側H26(2014)

雪圧(kN/m)Snow pressure

雪圧(kN/m)

20H25(2013)

柵に作用する雪圧S(kN/m)

朱鞠内The necessity for reviewing the current design method is thought to be low at present, because
the snow pressure stayed within the design snow pressure range during the observation period.
However, during the snowmelt period, the observed snow pressure often exceeded the calculated
value corresponding to the snow depth. To observe the changes in the snow pressure-snow depth
relationship, the necessity of continuing to observe the snow pressure is thought to be high.
Calculated snow pressure50

H24-H26観測雪圧

Snow pressure observed from 2012 to 2014

4030201000100200

積雪深H(cm)

300400Snow depth▲積雪深に対応した計算雪圧と観測雪圧(中山峠柵高3.5m)

The calculated snow pressure corresponding to the snow depth andthe observed snow pressure (Nakayama Pass snow fence: 3.5m high)国立研究開発法人土木研究所 寒地土木研究所

National Research and Development Agency Public Works Research Institute Civil Engineering Research Institute for Cold Region