Venkat

2

• HAUL ROADS: During the

life of the pit a haul road

must be maintained for

access.

• HAUL ROAD - SPIRAL

SYSTEM: Haul road is

arranged spirally along the

perimeter walls of the

pit.

Haul Road Design

3

• HAUL ROAD – SWITCH

BACK SYSTEM: Zigzag pattern

on one side of the pit.

• HAUL ROAD WIDTH: Function

of capacity of the road and the

size of the equipment. Haul road

width must be considered in the

overall pit design.

Haul Road Design

4

Haul Road Effect on Pit Limits

5

Considerations for Haul Road Design

• Visibility

• Stopping distances

• Vertical alignment

• Horizontal alignment

• Cross section

• Runaway-vehicle safetyprovisions

6

Sight Distances and StoppingDistances

• Vertical and horizontal curves designedconsidering sight distance and stoppingdistance

•

•

Sight distance is the extent of peripheral areavisible to the vehicle operator

Sight distance must be sufficient to enablevehicle traveling at a given speed to stopbefore reaching a hazard

7

Sight Distances and StoppingDistances

• On vertical curves, road surface limits sight

distance

••

•

Unsafe conditions remedied by lengthening curve

On horizontal curves, sight distance limited by

adjacent berm dike, rock cuts, trees, etc;

Unsafe conditions remedied by laying back bank or

removing obstacles

8

Sight Distance Diagrams

Sight distance diagrams for horizontal and vertical curves

9

Stopping Distances

• Stopping distances depend on truck breaking

capabilities, road slope and vehicle velocity

• Stopping distance curves can be derived

based on SAE service break maximum

stopping distances

10

Stopping DistanceCharacteristics

For example,stoppingdistance

characteristicsof vehicles of200,000 to400,000 poundsGVW

11

Stopping Distances

• Prior to final road layout, manufacturers of

vehicles that will use the road should be

contacted to verify the service brake

performance capabilities

Vertical Alignment

• Establishment of grades and vertical curves thatallow adequate stopping distances on all segmentsof the haul road

• Maximum sustained grades• Reduction in grade significantly increases vehicle uphill speed

• Reduction in grade decreases cycle time, fuel consumption, stresson mechanical components and operating costs

•

•

Reduction in grade increases safe descent speeds, increasingcycle time

The benefits of low grades offset by construction costs associatedwith low grades

12

13

Vehicle Performance Chart

14

Vehicle Retarder Chart

15

Vertical Alignment

• Maximum sustained grades

• Some states limit maximum grades to 15 to 20% and

sustained grades of 10%

• Most authorities suggest 10% as the maximum safe

sustained grade limitation

• Manufacturer studies show 8% grades result in the

lowest cycle time exclusive of constructionconsideration

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Vertical Alignment

• Maximum sustained grades

• Property boundaries, geology, topography, climate

must be considered on a case by case basis.

• Lower operating costs must be balanced against higher

capital costs of low grades.

• Truck simulators and mine planning studies over the

life of mine should be used to make the determinationof the appropriate grades

Vertical Curves

• Vertical curves smooth transitions from one

grade to another

• Minimum vertical curve lengths are based on

eye height, object height, and algebraic

difference in grade

17

18

Stopping Distance vs. Vertical Curve

For example,

vertical curve

controls 9 ft eyeheight (usually

minimum height

for articulated

haulage trucks of

200,000 to

400,000 pound ofGVW)

Horizontal Alignment

• Deals primarily with design of curves and

considers previously discussed radius, width,

and sight distance in addition to

superelevation

• Cross slopes also should be considered in thedesign

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20

Curves, Superelevation, andSpeed Limits

• Superelevation grade recommendations varybut should be limited to 10% or less becauseof traction limitations

•

•

Depending on magnitude of the side frictionforces at low speed, different values aresuggested for small radius curves

Kaufman and Ault suggest .04-.06 fpf(basically the normal cross slope)

21

Curves, Superelevation, andSpeed Limits

• CAT suggests higher slopes with traction

cautions and 10% maximum caution

• Again, where ice, snow, and mud are a

problem, there is a practical limit on the

degree of superelevation

22

Curve Superelevation

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Recommended Superelevation Rates

If superelevation is not used, speed limits should be set on curves.

24

Curves, Superelevation, andSpeed Limits

• Centrifugal forces of vehicles on curves are

counteracted by friction between tire an road and

vehicle weight as a result of superelevation

•

•

Theoretically, with superelevation, side friction

factors would be zero and centrifugal force is

balanced by the vehicle weight component

To reduce tire wear, superelevation or speed limits

on curves are required

25

Combinations of Alignments

• Avoid sharp horizontal curvature at or near the crestof a hill

•

•

••

Avoid sharp horizontal curves near the bottom ofsustained downgrades

Avoid intersections near crest verticals and sharphorizontal curvatures

Intersections should be made flat as possible

If passing allowed, grades should be constant andlong enough

26

Cross Section

•A stable road base is very important

• Sufficiently rigid bearing material should be

used beneath the surface

• Define the bearing capacity of the materialusing the California Bearing Ratio (CBR)

27

California Bearing Ratio

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Subbase Construction

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Cross Slopes

• Cross slopes provide adequate drainage and

range from ¼ to ½ inch drop per foot of

width (approximately .02 to .04 foot per foot)

• Lower cross slopes used on smooth surfaces

that dissipate water quickly and when ice or

mud is a constant problem

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Cross Slopes

• Higher cross slopes permit rapid drainage,reduce puddles and saturated sub-base, andare used on rough surfaces (gravel andcrushed rock) or where mud and snow arenot a problem

• High cross slopes can be particularlyproblematic with ice or snow on high grades(+5%)

31

Recommended Rate ofCross- Slope Change

Slope change should be gradual.

32

Width

• On straight or tangent segments, width

depends on

• Vehicle width

• Number of lanes

• Recommended vehicle clearance, which ranges

from 44 to 50% of vehicle width

33

Minimum Road Design Widthsfor Various Size Dump Trucks

34

Typical Design Haul Road Width

Typical

design haul-

road width

for two-way

traffic using

77.11-t (85-

st) trucks

35

Typical Haulageway Sections

36

Width

• Berm height and width as a function ofvehicle size and material type

••••

Ditch(es) added to basic recommendations

Runaway provisions may also add to width

Road wider on curves because of overhang

Minimum turning radius considered oncurves (should be exceeded)

37

Haulageway Widths on Curves

38

Safety Provisions - Berms

• Triangular or trapezoidal made by using local

material

• Stands at natural angle of repose of construction

material

• Redirects vehicle onto roadway

• Minimum height at rolling radius of tire

39

Berms

• Larger boulders backed with earthen material

• Near vertical face deflects vehicle for slight

angles of incidence

• Problems with damage and injury and

availability of boulders

• Minimum height of boulder at height of tire

allowing chassis impact

40

Runaway Provisions

• With adverse grades some safety provision should

be integrated to prevent runaway vehicles

•

•

•

Primary design consideration is required spacing

between protective provisions

Driver must reach a safety provision before truck

traveling too fast to maneuver

Maximum permissible speed depends on truck

design conditions and operator

41

Runaway Provisions

• Maximum permissible speed, equivalent

downgrade, and speed at break failure determine

distance between runaway truck safety provisions

• For example, at an equivalent downgrade of 5% and

a maximum speed of 40 mph,

Speed at Failure

Provision Spacing

10 mph

1,000 ft

20 mph

800 ft

(Kaufman and Ault)

42

Runaway Precautions

43

Median Runaway-VehicleProvision Berms

• Vehicle straddles collision berm and rides

vehicle to stop

••

•

Made of unconsolidated-screened fines

Critical design aspects spacing between

berms and height of berm

Height governed by height of undercarriage

and wheel track governed by largest vehicle

44

Median Runaway-VehicleProvision Berms

• Requires maintenance in freezing conditions

•Agitation to prevent damage to vehicle

• May cover berm in high rainfall areas

45

Escape Lanes

• Good tool for stopping runaway but

expensive to construct

•

•

Entrance from road is important; spacing,

horizontal, vertical curve and superelevation

are all considered in design

Deceleration mainly by adverse grade and

high rolling resistance material

46

Escape Lanes

• Length a function of grade and speed at

entrance and rolling resistance

• Stopping by level section median berm, sand

or gravel or mud pits, road bumps or manual

steering

47

Escape Lanes

48

Maintenance

• The road surface is

deformed by the constant

pounding of haulage

vehicles.

• A good road maintenanceprogram is necessary for

safety and economics.

49

Safety Considerations

• Dust, potholes, ruts, depressions, bumps, and

other conditions can impede vehicular

control.

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Economic Considerations

• The wear on every component is increased when avehicle travels over a rough surface.

• If the vehicle brakes constantly, unnecessary liningwear occurs as well.

51

Dust Control

• Dust may infiltrate brakes, air filters,hydraulic lifts, and other components ofmachinery.

• The abrasive effect of dust will result incostly cleaning or replacement of theseitems.

52

Deterioration Factors

• Weather

• Vehicles follow a

similar path

• Spillage

53

Motor Graders

•A motor grader

should be used to

maintain cross slopes,

remove spills, and to

fill and smooth

surface depressions asthey occur.

54

Road Drainage

• To avoid overflow, roadside ditches and

culverts should be periodically cleaned.

• Avoid erosion or saturation of subbase

materials.

Thanks