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Maintenance...
You can never completely prevent erosion of the
materials on a gravel road but using good design and materials along with good drainage can control the amount of erosion. Gravel roads require more frequent maintenance than paved
roads, especially after wet periods. Wheel motion shoves
material to the outside, leading to rutting, reduced
water-runoff and eventual destruction of the road if
unattended. If caught early enough, re-grading is usually sufficient to push the materials back into shape.
The worst erosion
generally occurs on steep grades. It is important that the surface
of the roadway allows
the water to drain to the sides into well-designed drainage
ditches or structures. Water cannot be allowed to run down the
middle of the road since the force of the running water can
quickly cause severe erosion of the surface layer and then the
aggregate base. Vehicle traffic also contributes to the
erosion of the surface layer. The extent of this erosion is
dependant on the volumes and size of the vehicles.
Periodic inspections of the entire road is recommended in
early March and August, especially after large storms, by
walking the entire length of the road examining culverts, cut
slopes, and the roadbed itself. Making sure drainage dips and
cross-sloping are still functioning and the roadbed is free of
ruts and ridges. Any blockage or damage to culverts or
drainage structures should be repaired immediately.
Dust...
When
there is insufficient moisture on the road, the fines no
longer act as a binder with the aggregates . These fines
are removed from the road surface by the action of traffic and
wind in the form of dust, leading to surface problems and
costly replacement of gravel.
The
best way to reduce the dust is to drive slowly - especially
when the road is dry. If you see dust blowing up behind
your vehicle, slow down.
Road
dust is also a health and environmental hazard. Dust kicked up
by traffic can travel several hundred feet into nearby homes
where it is one of the most common causes of allergies and hay
fever. This dust can also contaminate local waterways
and vegetation.
Water...
Regular cleaning of drainage structures is one of the most
important ways to maintain a good gravel roadway. Water is a
gravel road’s enemy and it needs to be conveyed efficiently
away from the roadway. Sediment, leaves, tree branches and
other debris commonly collect in drainage ditches, clogging them and causing a
buildup of water in the subgrade and aggregate base.
Clogging can also lead to
overflows during heavy rain, leading to washouts of the
roadway. The same can be said for blocked culverts and catch
basins. Drainage structures should be inspected and cleaned
regularly. Deferment of such activities could result in
thousands of dollars in repairs due to the erosion or failure
of the roadway structure, and thus have a major impact on the
surrounding environment.
Mud...
Mud season occurs during the
spring months of the year and is a result of excessive water
content in the road structure that freezes during the winter
months. As the warmer temperatures of spring arrive the water
in the roadway begins to melt from the top. Since the lower
layers are still frozen there is nowhere for this water to
drain. Since the surface layer contains a large proportion of
fines, the presence of water results in the formation of a
mud-slurry. The action of passing vehicles pumps this slurry
to the surface as the aggregates sink, destabilizing the
roadway structure and resulting in potholes, rutting and
erosion.
Mud season is inevitable with
gravel roads, but the extent of impact can be minimized
considerably by constructing an aggregate base of free
draining (gravel mixture with a minimal amount of fines)
materials that limit the water content and hence will not
freeze during the winter months.
Washboarding...
Washboarding is a common
challenge with gravel roads. Washboarding is the
formation of corrugations across the road and occurs on
roadways where the crust on the surface layer is dry and
crumbly as a result of the loss of the fines (primarily in the
form of dust) that are displaced by passing vehicles.
Washboarding is amplified in
areas experiencing high vehicle speeds or in areas where
vehicles are constantly braking and accelerating. Empty
pickup trucks with light rear ends traveling at higher speeds
appear to increase washboarding more so than other vehicles.
Washboarding vibrations in vehicles can become severe enough
to cause bolts to loosen or cracks to form in components.
Washboarding cannot be
completely prevented, but using well-graded surface materials
mixed with calcium chloride can minimize its reoccurrence.
Grading removes the corrugations, and reconstruction with
careful choice of good quality gravel can help keep them from
re-forming.
Calcium Chloride...
Calcium Chloride (CaCl2) has
been used for over 50 years to stabilize gravel road
materials. Calcium Chloride is classified as a salt that has
the ability to absorb moisture from the air. This moisture
binds the fines and aggregates together creating a harder and
more durable road surface layer. Calcium Chloride also resists
evaporation giving it a prolonged life in the roadway. Over
time the chemical penetrates the surface several inches,
adding a stabilization while reducing the effects of frost.
Calcium Chloride is seen as
an environmentally safe product when applied properly. The
State of Maine conducted a study on the migration of Calcium
Chloride in groundwater and found that concentrations were
directly related to the distance from the roadway. Calcium
Chloride tends to stay where it is placed when used for
roadway stabilization and there is no indication that negative
environmental impacts have occurred from its use for dust
control. However it is suggested that Calcium Chloride should
not be used in areas that often contain high, receding ground
water tables. A simple rule to follow to prevent the migration
of Calcium Chloride is not to apply it when heavy rain is
forecast in the following 36 hours. The presence of Calcium
Chloride in drinking water is not seen as a health hazard, but
can affect the aesthetics of taste and palatability.
Driving...
When you're driving up and down hills on a gravel road,
gravity plays a major role. As a general rule, it's a good
idea to shift down to low 2nd going up the hill and shift down
to low 1st going down.
When
you're driving uphill on a gravel road gravity slows you down.
The steeper and longer the grade, the more you will have to
use your lower gears to climb the hill. Keep a steady
even speed uphill so that you don't stall. If your car
has four wheel drive, use it going up the hills.
When
you're driving downhill, gravity causes the speed of your
vehicle to increase so you'll need to choose a safe speed,
then use a low gear and proper braking techniques, saving your
brakes so you will be able to slow or stop if needed. Be
sure to shift down to the low gear before starting down
the grade. Don't try to downshift after your speed has already
built up. Forcing an automatic transmission into a lower gear
at high speed could damage the transmission and also lead to
loss of all engine braking effect.
Driving on a gravel road requires paying attention to surface
variations because it is easier to lose control than on a
paved road. In addition to potholes, ruts and loose stone,
challenges associated with driving on gravel roads include:
-
Sharp stones thrown up by the wheels and damaging the
underside of vehicles
-
Stones skipping up when two vehicles pass and hitting the
vehicle body, lights or windshield
-
Dust thrown from passing vehicles reducing visibility
-
Loss of vehicle control on
washboard surfaces
-
Skidding on mud after
a rain
The best way to maintain safe
control of your vehicle is to
drive slowly. |