Terrain assessment, drainage and erosion - Geotechnical Investigation and Design Tables - page 189

Table 15.3 ( Continued )

Development type Grade % Deg. ◦ Vert. : Horiz.

Site development 15 8.5 1V : 6.7H

Standard wheel tractor
Acceptable for recreational paths and trails
Upper limit for camp and picnic areas

Housing site development 20 11.3 1V : 5.0H

Lot driveways 25 14.0 1V : 4.0H

Upper limit for recreational paths and trails
Typical limit for rollers to compact

Benching into slopes required 33 18.4 1V : 3.0H

Planting on slopes become difficult without mesh/benches 50 26.6 1V : 2.0H

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Construction equipment has different levels of operating efficiency depending on
grade, and riding surface.

15.4 Equivalent gradients for construction equipment
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The rolling resistance is the force that must be overcome to pull a wheel on the
ground. This depends on the gradient of the site and the nature of the road.

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Rolling Resistance = Rolling Resistance Factor × Gross Vehicle Weight.

Table 15.4 Rolling resistance and equivalent gradient of wheeled plant (Horner, 1988).

Haul road conditions Rolling resistance factor

Surface Description Kg/t An equivalent

gradient

Hard, smooth Stabilized surfaced roadway, no penetration under 20 2.0%

load, well maintained

Firm, smooth Rolling roadway with dirt or light surfacing, some 32.5 3.0%

flexing under load, periodically maintained

With snow Packed 25 2.5%

Loose 45 4.5%

Dirt roadway Rutted, flexing under load, little maintenance, 50 5.0%

25 to 50 mm tyre penetration

Rutted dirt Rutted, soft under travel, no maintenance, 75 7.5%

roadway 100 to 150 mm tyre penetration

Sand/Gravel surface Loose 100 10%

Clay surface Soft muddy rutted. No maintenance 100-200 10-20%

15.5 Development procedures
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The slope is usually the key factor in consideration of stability. However geology,
aspect, drainage etc also affect the stability of the slopes.