Transcript FOREST ROADS IN WINTER

FOREST ROADS IN WINTER
Frank MacCulloch
Forestry Civil Engineering
Worst Winter in 100 years?
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Frost Heave
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ROADEX -Managing spring thaw weakening on low volume roads
Field tests at Garvault
Percostation in
Scotland
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Frost Heave
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Frost heave and thaw settlement
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Public Roads
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Wet or Dry Snow?
 Snow...wet or dry landing on frozen road or
wet road!
 Snow falling onto an unfrozen road has limited
impact on road surface when it thaws
• If the road is frozen prior to the snow fall
surface erosion and damage can occur when
the thaw takes place.
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Access
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Self Help?
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Snow Clearing; GB style
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Snow Clearing; Sweden
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Grader on Public Road!
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Lorry Blade
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Keep drains clear
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Keep Drains clear!
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How chlorides can cause failures on gravel road
Salty water penetrates into the road, parts with higher amount of salt adsorb more
water due to osmotic suction
Wearing course
Base course
Subgrade
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Due to uneven distribution of salt road surface does not freeze evenly and parts
with smaller salt amount freeze first
Wearing
course
Base
course
Subgrade
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Cryosuction is developed, which adsorps water beneath and aside from the unfrozen
parts that have more water
Wearing
course
Base
course
Subgrade
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Segregation ice is developed causing frost heave and uneveness – and cause
damages in the top layers. ”Bumps” are smaller at wheelpaths due to dynamic loading.
Wearing
course
Base
course
Subgrade
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Bound structures get cracks allowing more water to penetrate in the road
Wearing
course
Base
course
Subgrade
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Whole structure freeze and differential ”bumps” increase due to osmotic forces
Wearing
course
Base
course
Subgrade
And when this material thaws it has > 100 % water in its pores and becomes totally
plastic.
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Impact of Salt
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Access
• Studded tyres cause pavement wear in the
range of 2-10g/km/vehicle
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Snow Chains
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Summary
• Good drainage essential
• Keep trees well back, and road open to wind and sun.
• Plan for Winter
• Do you need to access the forest?
• Risk Assessment!
• Do not use salt on Forest Roads!
• Spreading salt is a waste of money and poses an
environmental risk
• Salt will cause aggregate disintegration with porous
aggregates
• Do not access the forest during periods of thaw (Dispensation
possible for lorries fitted with Tyre Pressure Technology)
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Preparing for Winter
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Thanks for listening
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