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Snow deflector built at the edge of a road cut
Cold Regions Science and Technology, 12 (1986) 121-129
121
Elsevier Science Publishers B.V., Amsterdam - Printed in The Netherlands
SNOW DEFLECTOR
BUILT AT THE EDGE OF A ROAD CUT
Yutaka Anno* Construction Machinery Institute of HokkaJdo Development Bureau, Higashi, 2-jo, 8-chome, Tsukisamu, Toyohiraku, Sapporo (Japan)
(Received January 18, 1985; accepted i n revisedform September 19, 1985)
ABSTRACT
This paper describes experiments with a solid snow fence for snowdrift prevention on a road cuL Solid fence has seldom been used for prevention o f snowdrifts because the fence soon becomes saturated and ineffective. However, a modeling experiment with a solid fence built at the shoulder edge o f a road cut indicated the effect o f the fence on blowing snow particles upward. Therefore, it was easily predicted that the effect could prevent the snowdrift formation on a full-scale road cut. The result o f the field experiment using the same type o f snow fence showed the same effect as shown in the modeling experiment.
INTRODUCTION Figure 1 shows an accident which was caused by snowdrift formation in a road cut located in southern Hokkaido, Japan. The accident killed three men and a woman who were awaiting the arrival o f snow plows. The snowstorm was so heavy that the people died from breathing the exhaust gas after the exhaust pipe was buried under snow. It was considered that it took only a few hours for them to be killed. Because a road cut may be regarded as a trench which capures snow particles, the snowdrift rate *Department of Civil Engineering, Univ. of N.H., Durham, NH 03824 (U.S.A.) 0165-232X/86/$03.50
there becomes much larger than that of other places. Therefore, the road is often blocked by snowdrift formation and visibility decreases in road cuts in Hokkaido or in northern Honshu, Japan. One of the most popular methods of snowdrift prevention on a road is building a collecting snow fence on the windward side of the road, with an appropriate interval between the road and the fence (Mellor, 1965). With this method, a large snowdrift is formed in the interval between the road and the fence; the road is protected by upwind deposition. This method is a kind of snow dam, but it has the following disadvantages: (1) snowdrift preveming effect cannot be expected after the snow fence is saturated; (2) a long distance between the snow fence and the road is necessary. Another effective method is a snow shelter, or shed, which covers the road completely, but construction of such a shelter is very expensive. The author proposes the use of a solid fence which is built at the shoulder edge of a cut and inclined a little. Solid fence has seldom been used because the fence soon becomes saturated and thus ineffective (Jumikis, 1970). However, modeling results using activated clay particles as model snow (Anno and Kokubun, 1978) suggested that a tall inclined solid fence ( 5 - 1 0 m in height) was very effective in the prevention of snowdrift formation. There was also an increase of visibility on the road because transported snow particles from the windward side were blown upward, then over the road. Since a sufficient fence height from the road surface can be obtained for a solid fence built at a shoulder edge of a cut,
© 1986 Elsevier Science Publishers B.V.
122
Fig. 1. An accident which killed four people burying them under snowdrift formed on a road cut. it is considered that this has the same effect in snowdrift prevention as a tall inclined solid fence. In this paper the snowdrift preventing effect of a solid fence in a road cut is examined by a modeling experiment on a scale of 1:500. The effect is then validated by a full-scale experiment.
1. MODELING EXPERIMENT In order to examine the snowdrift-preventing effect of a solid fence in a road cut, a qualitative modeling experiment was conducted.
1.1 Modeling site The modeling site was Okushunbetsu, Tesikagacho of route 241, in east Hokkaido, where the road was very often blocked by snowdrift formation. The daily maximum wind speed there in winter is in the range from 7 - 1 5 m/s at a height of 1 m above the snow surface. The windward area was meadow for a distance of a few kilometres. The prevailing wind direction was northwest in winter, which was at 45 ° to the road cut direction.
1.2 Modeling apparatus and procedure The model snow used in this expertment was activated clay, which Anno and Konishi (1981) reported as suitable for the modeling of a snowdrift. The properties are as follows: the mode grain diameter is 1.5 /lm; grain and bulk densities are 2.51 and 0.65 Mg/m 3, the specific surface area is 2 0 0 300 m 2/g, the angle o f repose is 4 0 - 5 0 °. An open-circuit type of wind tunnel, with crosssection 0.8 m × 0.8 m, was used in this experiment (see Anno and Konishi, 1981). The activated clay particles were injected by compressed air to the testing section of the wind tunnel at the rate of 230 g/min from the injecting nozzle located 3 m to windward o f the model road. The road cut was modeled on a scale of 1/500, which was a suitable scale in the modeling of a snowdrift using activated clay particles (Anno and Konishi, 1981). The meadow of the model was roughened by glueing cloth to its surface, and the road surface was smoothed in accordance with Anno's modeling criteria (Anno, 1984). Figures 2 and 3 show the photograph of the model road cut and its cross section respectively.
123
Fig. 2. Model road cut on scale of 1:500. Its prototype is located in Eastern Hokkaido.
SCALE
I : 500
,(--, \ \
I
Up/Urn = Am" U~pt/Ap" (-f*mt
(1)
Tp/Tm = Qm "rim "pp'F2wp/Qp"Pm "F2wm
(2)
FENCE
DOWNWIND
I Fig. 3. Cross-section of the model road cut and the solid snow fence, 6 mm in height, 45 ° downwind inclination. Model wind speed was controlled as follows. In order to produce a uniform and even accumulation o f model snow on the windward side of the model road, the wind speed was maintained at 1 m/s at a height of 10 mm for 25 min, then gradually increased in increments o f 0.7 m/s for each 5 min period. When the wind speed reached 2.4 m/s, the model snow particles began to drift toward the lee side. The final wind speed was maintained at 5.2 m/s. These model values are estimated from their full scale values using Anno's modeling criteria as follows. Anno proposed the following two equations for calculating the ratio of wind speed and storm duration between the model and the prototype.
In eqn. (1), Up is the full-scale wind speed at a height of 1 m (m/s), U m is the model wind speed at a height of 10 mm in the wind tunnel (m/s); Ap and Am are the prototype and model coefficients o f proportionality which relate Up, Um and friction speeds, U~, U*m (m/s) respectively; TABLE 1 Prototype values of wind speed and storm duration estimated from their model values wind speed
storm duration
model
prototype
1.0 m/s
2.5 m/s
1.7 2.4 3.1 3.8 4.5 5.2
4.2 5.9 7.6 9.3 11.1 12.8
model
prototype
(25 min) 5 5 5 5 5 5 30 total
50 hours 50 50 50 50 50 300 total
124 U~p and Ut*m are threshold friction speeds of the model and prototype (m/s). In eqn. (2), Q is the snow drift rate (g/m-min), Fw is the width of fence (m), p is the bulk density of snow particles (Mg/ m3), and r/ is the object's collection coefficient for snow particles. The wind speed ratio, Up/Urn, is calculated at 1:2.46 when activated clay particles were used as model snow from eqn. (1), because Am, Ap, U* t and Upt were 0.55, 0.4, 0.112 and 0.200 m/s respectively (Anne, 1984). Qm is expressed as 0.56 Uam with injection of model snow particles in the wind tunnel (Anne, 1985), while Qp is expressed as 1.2 U~, pp is 0.4 Mg/m 3 . Fwp/Fwm is 500, r/m is estimated as 12.5% by dividing the weight of the model snowdrift on the model road cut by the weight of the model
snow particles which enter the cut. ~/p iS assumed to be about 100%, because Kobayashi (1972) reported that the trench captures most o f the saltating particles. Therefore, Tp/Tm would be estimated as 603, and prototype storm durations are predicted as in Table 1. Figure 4 shows the model snowdrift formed in the road cut when the model wind speed reached 5.2 m/s. As shown in the figure, the road cut is buried under snow, especially at the section A in the figure. This modeling result is qualitatively similar to its prototype because the snowplow operator reported that the snowdrift is deepest at the section A in the prototype road cut. The snowstorm modeled in this experiment might be one of rare severity, since such a large snowdrift has been seldom observed at the site. There-
Fig. 4. Model snowdrift formed on the model road cut which is qualitatively similar to its prototype.
125
Fig. 5. Model snow particles blown upward by the model snow fence.
fore, if snowdrift formation is prevented by a snow fence under such a severe condition, it proves that the fence has sufficient capacity for protecting the road cut from ordinary snowstorms. In order to prevent snowdrift formation, the model snow fence as shown in Fig. 3 was built at the windward shoulder edge of the road cut from point a to b in Fig. 4. Figure 5 shows the cross section of the flow pattern of drifting snow blown upward and over the road by the strong wind deflected by the fence, this being visualized using adherence of activated clay particles on a plastic plate placed parallel to the wind direction. Figure 6 shows the road surface after building the model snow fence. As shown in this figure, the snowdrift formed before building the fence disappeared by the blowing effect of the fence, suggesting that a solid fence built at the shoulder edge of the road cut is very effective for prevention of snowdrift formation there.
The figure also shows other interesting phenomena caused by drifting snow particles. For examples, (M) in Fig. 4 shows waves, (N) shows ripples, and (O) shows a wind scoop around a house. These surface patterns are often observed after snowdrifting.
2. FIELD E X P E R I M E N T 2.1 Study site and snow fence
A prototype snow fence was built at the shoulder edge of a road cut on prefectural road 108, Akita prefecture, northern Honshu, Japan. This road cut was often blocked by: (a) collapse of snow comices formed at the windward shoulder edge of the cut, (b) snowdrift formation, and (c) decrease of visibility caused by drifting snow. Figure 7 shows
126
Fig. 6. The model snowdrift slaown in Fig. 4 disappeared after constructing the model snow fence.
the snowdrift formed on the road cut, which reached about 4 m in height, and blocked the road 5 - 6 times per winter. Prevailing wind direction was northwesterly, which was the same direction to the road cut as was used in the model. The daily maximum wind speed was 7 - 1 2 m/s at a height of 1 m in winter. The solid snow fence, 4.1 m in height, 470 m long and inclined 30 ° downwind, was built on a concrete base in order to withstand the strong wind and snow load. A schematic view of fence and road cut is shown in Fig. 8.
2.2 Result
The drift profile after building the snow fence is compared with that before building the fence in Figure 8. By January 18 a large hollow was created before the fence, so the upwind drift did not attach
to the fence. However, with lapse o f time the hollow became closer to the fence. Finally, the fence was buried to 80% o f its height, and the drift reached an equilibrium profile by March 18, as shown in Fig. 8, because the wind is so strong at the top of the fence that snow particles are blown upward. This hollow was observed in the modeling experiment, but the depth o f the hollow was not so great as the prototype hollow because of greater inclination of the model fence. The snow deposit shown downwind of the fence was formed by snow fall, not by drifting. Figure 9 shows the blowing effect of a solid fence. Snow particles transported from the windward side were blown upward, as seen in this figure as well as in the modeling. As a result, the road cut was protected from snowdrift formation, from snow comice formation and from reduction of visibility, as shown in Fig. 10.
127
Fig. 7. Cut-view of the snowdrift formed on road cut of prefectural road 108, Akita. Its height reached 4 m in 1982.
~---:] WtTHOLIT FENCE FEBRU4Ny 16, INI ~ FENCE ~:M iN, )~e~
.~(~ ~
ot' / o
OOWNW)NO .................. ~:
\
\ \
Y ~,
' ) . oICEl C ° ~ , ' : E ~ -
"-~
....
UPW~NO
.
.-,.,
................ :.~:i~:.~ :.-.:.~.
GROUND
Fig. 8. Change of prototype drift profile with lapse of time, the prototype snow fence.
a n d cross-section o f
CONCLUSION Until now, solid fences have seldom been used because they have insufficient capacity for depositing large amounts of snow. However, this study revealed that if a solid fence is used for the deflection of drifting snow particles, it becomes very effective in preventing snowdrift formation. A solid fence built at a shoulder edge of a cut has the following three advantages, which are provided by the upward deflection of particles:
(1) Increased visibility on road surface. (2) Prevention of snowdrift formation on road surface. (3)Prevention of snow cornice formation at the windward shoulder of the cut. For the section studied in the field experiment, these advantages o f the solid fence reduced the cost o f the snow removal by one-third compared with the previous year, and there were no blockages after fence construction, compared with 5 or 6 blockages per season previously. The experimental result also shows that the precise prediction o f snowdrift formation becomes feasible by means of activated clay particles and Anno's modeling criteria.
ACKNOWLEDGEMENTS The author expresses his hearty thanks to Riken Kogyo Inc., for permission to use the photographs
128
Fig. 9. The prototype fence blows snow particles upward as does the model fence.
Fig. 10. Snowdrift formed before constructing the solid fence has disappeared after constructing it. The cost o f snow removal is reduced to 1/3 o f that before the construction, and 5 - 6 times blockage per year is reduced to 0.
129
o f the field e x p e r i m e n t o f the snow fence. He is also grateful to Dr. Malcolm Mellor o f C R R E L , for helpful suggestions.
REFERENCES Anno, Y. (1984). Requirements for modeling of a snowdrift. Cold Reg. Sci. Technol., 8(3): 241-252. Anno, Y. (1985). Modeling of a snowdrift by means of activated clay particles. Annals of Glaciology (in press). Anno, Y. and Kokubun, M. (1978). Modeling the Method of Snowdrift-Prevention at Okayama, Iwamizawa, in Route 12. Report of Construction Machinery Institute, 68 pp. (in Japanese).
Anno, Y. and Konishi, T. (1981). Modeling the effect of a snowdrift-preventing forest and a snow fence by means of activated clay particles. Cold Reg. Sci. Technol., 5(1): 43-58. Jumikis, A.R. (1970). Aerodynamic snow fences to control snowdrift on roads. In: Proc. of Snow Removal and Ice Control Research, Hanover, New Hampshire, April 8-10, 1970. CRREL and HRB Special Report 115, National Research Council, Washington, D.C., pp. 210-219. Kobayashi, D. (1972). Studies of snow transport in low-level drifting snow. Contributions from the Institute of Low Temperature Science, Series A, No. 24, pp. 1-58. Mellor, M. (1965). Blowing Snow. Cold Regions Science and Engineering, Part III, Sec. A3C, (CRREL, Hanover), p. 79.
121
Elsevier Science Publishers B.V., Amsterdam - Printed in The Netherlands
SNOW DEFLECTOR
BUILT AT THE EDGE OF A ROAD CUT
Yutaka Anno* Construction Machinery Institute of HokkaJdo Development Bureau, Higashi, 2-jo, 8-chome, Tsukisamu, Toyohiraku, Sapporo (Japan)
(Received January 18, 1985; accepted i n revisedform September 19, 1985)
ABSTRACT
This paper describes experiments with a solid snow fence for snowdrift prevention on a road cuL Solid fence has seldom been used for prevention o f snowdrifts because the fence soon becomes saturated and ineffective. However, a modeling experiment with a solid fence built at the shoulder edge o f a road cut indicated the effect o f the fence on blowing snow particles upward. Therefore, it was easily predicted that the effect could prevent the snowdrift formation on a full-scale road cut. The result o f the field experiment using the same type o f snow fence showed the same effect as shown in the modeling experiment.
INTRODUCTION Figure 1 shows an accident which was caused by snowdrift formation in a road cut located in southern Hokkaido, Japan. The accident killed three men and a woman who were awaiting the arrival o f snow plows. The snowstorm was so heavy that the people died from breathing the exhaust gas after the exhaust pipe was buried under snow. It was considered that it took only a few hours for them to be killed. Because a road cut may be regarded as a trench which capures snow particles, the snowdrift rate *Department of Civil Engineering, Univ. of N.H., Durham, NH 03824 (U.S.A.) 0165-232X/86/$03.50
there becomes much larger than that of other places. Therefore, the road is often blocked by snowdrift formation and visibility decreases in road cuts in Hokkaido or in northern Honshu, Japan. One of the most popular methods of snowdrift prevention on a road is building a collecting snow fence on the windward side of the road, with an appropriate interval between the road and the fence (Mellor, 1965). With this method, a large snowdrift is formed in the interval between the road and the fence; the road is protected by upwind deposition. This method is a kind of snow dam, but it has the following disadvantages: (1) snowdrift preveming effect cannot be expected after the snow fence is saturated; (2) a long distance between the snow fence and the road is necessary. Another effective method is a snow shelter, or shed, which covers the road completely, but construction of such a shelter is very expensive. The author proposes the use of a solid fence which is built at the shoulder edge of a cut and inclined a little. Solid fence has seldom been used because the fence soon becomes saturated and thus ineffective (Jumikis, 1970). However, modeling results using activated clay particles as model snow (Anno and Kokubun, 1978) suggested that a tall inclined solid fence ( 5 - 1 0 m in height) was very effective in the prevention of snowdrift formation. There was also an increase of visibility on the road because transported snow particles from the windward side were blown upward, then over the road. Since a sufficient fence height from the road surface can be obtained for a solid fence built at a shoulder edge of a cut,
© 1986 Elsevier Science Publishers B.V.
122
Fig. 1. An accident which killed four people burying them under snowdrift formed on a road cut. it is considered that this has the same effect in snowdrift prevention as a tall inclined solid fence. In this paper the snowdrift preventing effect of a solid fence in a road cut is examined by a modeling experiment on a scale of 1:500. The effect is then validated by a full-scale experiment.
1. MODELING EXPERIMENT In order to examine the snowdrift-preventing effect of a solid fence in a road cut, a qualitative modeling experiment was conducted.
1.1 Modeling site The modeling site was Okushunbetsu, Tesikagacho of route 241, in east Hokkaido, where the road was very often blocked by snowdrift formation. The daily maximum wind speed there in winter is in the range from 7 - 1 5 m/s at a height of 1 m above the snow surface. The windward area was meadow for a distance of a few kilometres. The prevailing wind direction was northwest in winter, which was at 45 ° to the road cut direction.
1.2 Modeling apparatus and procedure The model snow used in this expertment was activated clay, which Anno and Konishi (1981) reported as suitable for the modeling of a snowdrift. The properties are as follows: the mode grain diameter is 1.5 /lm; grain and bulk densities are 2.51 and 0.65 Mg/m 3, the specific surface area is 2 0 0 300 m 2/g, the angle o f repose is 4 0 - 5 0 °. An open-circuit type of wind tunnel, with crosssection 0.8 m × 0.8 m, was used in this experiment (see Anno and Konishi, 1981). The activated clay particles were injected by compressed air to the testing section of the wind tunnel at the rate of 230 g/min from the injecting nozzle located 3 m to windward o f the model road. The road cut was modeled on a scale of 1/500, which was a suitable scale in the modeling of a snowdrift using activated clay particles (Anno and Konishi, 1981). The meadow of the model was roughened by glueing cloth to its surface, and the road surface was smoothed in accordance with Anno's modeling criteria (Anno, 1984). Figures 2 and 3 show the photograph of the model road cut and its cross section respectively.
123
Fig. 2. Model road cut on scale of 1:500. Its prototype is located in Eastern Hokkaido.
SCALE
I : 500
,(--, \ \
I
Up/Urn = Am" U~pt/Ap" (-f*mt
(1)
Tp/Tm = Qm "rim "pp'F2wp/Qp"Pm "F2wm
(2)
FENCE
DOWNWIND
I Fig. 3. Cross-section of the model road cut and the solid snow fence, 6 mm in height, 45 ° downwind inclination. Model wind speed was controlled as follows. In order to produce a uniform and even accumulation o f model snow on the windward side of the model road, the wind speed was maintained at 1 m/s at a height of 10 mm for 25 min, then gradually increased in increments o f 0.7 m/s for each 5 min period. When the wind speed reached 2.4 m/s, the model snow particles began to drift toward the lee side. The final wind speed was maintained at 5.2 m/s. These model values are estimated from their full scale values using Anno's modeling criteria as follows. Anno proposed the following two equations for calculating the ratio of wind speed and storm duration between the model and the prototype.
In eqn. (1), Up is the full-scale wind speed at a height of 1 m (m/s), U m is the model wind speed at a height of 10 mm in the wind tunnel (m/s); Ap and Am are the prototype and model coefficients o f proportionality which relate Up, Um and friction speeds, U~, U*m (m/s) respectively; TABLE 1 Prototype values of wind speed and storm duration estimated from their model values wind speed
storm duration
model
prototype
1.0 m/s
2.5 m/s
1.7 2.4 3.1 3.8 4.5 5.2
4.2 5.9 7.6 9.3 11.1 12.8
model
prototype
(25 min) 5 5 5 5 5 5 30 total
50 hours 50 50 50 50 50 300 total
124 U~p and Ut*m are threshold friction speeds of the model and prototype (m/s). In eqn. (2), Q is the snow drift rate (g/m-min), Fw is the width of fence (m), p is the bulk density of snow particles (Mg/ m3), and r/ is the object's collection coefficient for snow particles. The wind speed ratio, Up/Urn, is calculated at 1:2.46 when activated clay particles were used as model snow from eqn. (1), because Am, Ap, U* t and Upt were 0.55, 0.4, 0.112 and 0.200 m/s respectively (Anne, 1984). Qm is expressed as 0.56 Uam with injection of model snow particles in the wind tunnel (Anne, 1985), while Qp is expressed as 1.2 U~, pp is 0.4 Mg/m 3 . Fwp/Fwm is 500, r/m is estimated as 12.5% by dividing the weight of the model snowdrift on the model road cut by the weight of the model
snow particles which enter the cut. ~/p iS assumed to be about 100%, because Kobayashi (1972) reported that the trench captures most o f the saltating particles. Therefore, Tp/Tm would be estimated as 603, and prototype storm durations are predicted as in Table 1. Figure 4 shows the model snowdrift formed in the road cut when the model wind speed reached 5.2 m/s. As shown in the figure, the road cut is buried under snow, especially at the section A in the figure. This modeling result is qualitatively similar to its prototype because the snowplow operator reported that the snowdrift is deepest at the section A in the prototype road cut. The snowstorm modeled in this experiment might be one of rare severity, since such a large snowdrift has been seldom observed at the site. There-
Fig. 4. Model snowdrift formed on the model road cut which is qualitatively similar to its prototype.
125
Fig. 5. Model snow particles blown upward by the model snow fence.
fore, if snowdrift formation is prevented by a snow fence under such a severe condition, it proves that the fence has sufficient capacity for protecting the road cut from ordinary snowstorms. In order to prevent snowdrift formation, the model snow fence as shown in Fig. 3 was built at the windward shoulder edge of the road cut from point a to b in Fig. 4. Figure 5 shows the cross section of the flow pattern of drifting snow blown upward and over the road by the strong wind deflected by the fence, this being visualized using adherence of activated clay particles on a plastic plate placed parallel to the wind direction. Figure 6 shows the road surface after building the model snow fence. As shown in this figure, the snowdrift formed before building the fence disappeared by the blowing effect of the fence, suggesting that a solid fence built at the shoulder edge of the road cut is very effective for prevention of snowdrift formation there.
The figure also shows other interesting phenomena caused by drifting snow particles. For examples, (M) in Fig. 4 shows waves, (N) shows ripples, and (O) shows a wind scoop around a house. These surface patterns are often observed after snowdrifting.
2. FIELD E X P E R I M E N T 2.1 Study site and snow fence
A prototype snow fence was built at the shoulder edge of a road cut on prefectural road 108, Akita prefecture, northern Honshu, Japan. This road cut was often blocked by: (a) collapse of snow comices formed at the windward shoulder edge of the cut, (b) snowdrift formation, and (c) decrease of visibility caused by drifting snow. Figure 7 shows
126
Fig. 6. The model snowdrift slaown in Fig. 4 disappeared after constructing the model snow fence.
the snowdrift formed on the road cut, which reached about 4 m in height, and blocked the road 5 - 6 times per winter. Prevailing wind direction was northwesterly, which was the same direction to the road cut as was used in the model. The daily maximum wind speed was 7 - 1 2 m/s at a height of 1 m in winter. The solid snow fence, 4.1 m in height, 470 m long and inclined 30 ° downwind, was built on a concrete base in order to withstand the strong wind and snow load. A schematic view of fence and road cut is shown in Fig. 8.
2.2 Result
The drift profile after building the snow fence is compared with that before building the fence in Figure 8. By January 18 a large hollow was created before the fence, so the upwind drift did not attach
to the fence. However, with lapse o f time the hollow became closer to the fence. Finally, the fence was buried to 80% o f its height, and the drift reached an equilibrium profile by March 18, as shown in Fig. 8, because the wind is so strong at the top of the fence that snow particles are blown upward. This hollow was observed in the modeling experiment, but the depth o f the hollow was not so great as the prototype hollow because of greater inclination of the model fence. The snow deposit shown downwind of the fence was formed by snow fall, not by drifting. Figure 9 shows the blowing effect of a solid fence. Snow particles transported from the windward side were blown upward, as seen in this figure as well as in the modeling. As a result, the road cut was protected from snowdrift formation, from snow comice formation and from reduction of visibility, as shown in Fig. 10.
127
Fig. 7. Cut-view of the snowdrift formed on road cut of prefectural road 108, Akita. Its height reached 4 m in 1982.
~---:] WtTHOLIT FENCE FEBRU4Ny 16, INI ~ FENCE ~:M iN, )~e~
.~(~ ~
ot' / o
OOWNW)NO .................. ~:
\
\ \
Y ~,
' ) . oICEl C ° ~ , ' : E ~ -
"-~
....
UPW~NO
.
.-,.,
................ :.~:i~:.~ :.-.:.~.
GROUND
Fig. 8. Change of prototype drift profile with lapse of time, the prototype snow fence.
a n d cross-section o f
CONCLUSION Until now, solid fences have seldom been used because they have insufficient capacity for depositing large amounts of snow. However, this study revealed that if a solid fence is used for the deflection of drifting snow particles, it becomes very effective in preventing snowdrift formation. A solid fence built at a shoulder edge of a cut has the following three advantages, which are provided by the upward deflection of particles:
(1) Increased visibility on road surface. (2) Prevention of snowdrift formation on road surface. (3)Prevention of snow cornice formation at the windward shoulder of the cut. For the section studied in the field experiment, these advantages o f the solid fence reduced the cost o f the snow removal by one-third compared with the previous year, and there were no blockages after fence construction, compared with 5 or 6 blockages per season previously. The experimental result also shows that the precise prediction o f snowdrift formation becomes feasible by means of activated clay particles and Anno's modeling criteria.
ACKNOWLEDGEMENTS The author expresses his hearty thanks to Riken Kogyo Inc., for permission to use the photographs
128
Fig. 9. The prototype fence blows snow particles upward as does the model fence.
Fig. 10. Snowdrift formed before constructing the solid fence has disappeared after constructing it. The cost o f snow removal is reduced to 1/3 o f that before the construction, and 5 - 6 times blockage per year is reduced to 0.
129
o f the field e x p e r i m e n t o f the snow fence. He is also grateful to Dr. Malcolm Mellor o f C R R E L , for helpful suggestions.
REFERENCES Anno, Y. (1984). Requirements for modeling of a snowdrift. Cold Reg. Sci. Technol., 8(3): 241-252. Anno, Y. (1985). Modeling of a snowdrift by means of activated clay particles. Annals of Glaciology (in press). Anno, Y. and Kokubun, M. (1978). Modeling the Method of Snowdrift-Prevention at Okayama, Iwamizawa, in Route 12. Report of Construction Machinery Institute, 68 pp. (in Japanese).
Anno, Y. and Konishi, T. (1981). Modeling the effect of a snowdrift-preventing forest and a snow fence by means of activated clay particles. Cold Reg. Sci. Technol., 5(1): 43-58. Jumikis, A.R. (1970). Aerodynamic snow fences to control snowdrift on roads. In: Proc. of Snow Removal and Ice Control Research, Hanover, New Hampshire, April 8-10, 1970. CRREL and HRB Special Report 115, National Research Council, Washington, D.C., pp. 210-219. Kobayashi, D. (1972). Studies of snow transport in low-level drifting snow. Contributions from the Institute of Low Temperature Science, Series A, No. 24, pp. 1-58. Mellor, M. (1965). Blowing Snow. Cold Regions Science and Engineering, Part III, Sec. A3C, (CRREL, Hanover), p. 79.