Figure B2. Removing snow to show deformed chalk holes.
the direction that the vehicle is moving but parallel to the ground, and downward
or lower infers motion towards the ground. The deformation around a rolling wheel
is extremely complex and there seem to be four areas to consider. These are the area
under the wheel (the rut area), the area in front of the wheel, and the upper and lower
areas adjacent to the wheel sides. The deformation in front of the wheel and to the
sides of the wheel in the upper part of the snow cover are related to each other, to
the snow depth and the wheel sinkage.
Looking first at the snow under the wheel rut, one can see that the snow at the
centerline of the wheel is pushed forward and downward as the wheel rolls forward.
Snow that is off the centerline is pushed off at an increasing angle by the compacting
snow closer to the centerline. This is seen in the chalk exposed in the area of the wheel
rut. The chevron shapes are created because the snow near the center of the snow
pack is pushed out further (perpendicularly and forward) than the snow near the
snow or ground surfaces. As forward motion continues, the upper snow is pushed
Table B1. Vehicle and wheel characteristics.
CRREL Instrumented Vehicle (CIV), 1977 Jeep Cherokee
Tires: Michelin LT 235XCH4, 179 kPa
Radius: 37.5 cm
Maximum deformed width: 26 cm
CRREL Support Truck, 1989 Chevrolet 3/4 ton pickup
Tires: LT 245/75R16 M&S
Radius: 37 cm
Maximum deformed width: not recorded
HEMTT, M997 Heavy Expanded Mobility Tactical Truck
Tires: Michelin 16.0 R20
Radius: not recorded
Maximum deformed width: 48 cm