Downloaded 1,712 times
Uploaded byRAMANA M V
Haul road design
The document discusses various considerations for designing haul roads in surface mines. It covers types of haul road systems, factors that influence haul road width like vehicle size and capacity, alignment best practices for grades, curves and sight distances, cross section elements, and safety provisions. Proper haul road design requires balancing factors like construction costs, vehicle performance, and safety.
More Related Content
Haul road design
- 1.
- 2. Haul Road Design • 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. 2
- 3. Haul Road Design • 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. 3
- 4. Haul Road Effecton Pit Limits 4
- 5. Considerations for HaulRoad Design • Visibility • Stopping distances • Vertical alignment • Horizontal alignment • Cross section • Runaway-vehicle safety provisions 5
- 6. Sight Distances andStopping Distances • Vertical and horizontal curves designed considering sight distance and stopping distance • Sight distance is the extent of peripheral area visible to the vehicle operator • Sight distance must be sufficient to enable vehicle traveling at a given speed to stop before reaching a hazard 6
- 7. Sight Distances andStopping Distances • 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 7
- 8. Sight Distance Diagrams Sightdistance diagrams for horizontal and vertical curves 8
- 9. Stopping Distances • Stoppingdistances depend on truck breaking capabilities, road slope and vehicle velocity • Stopping distance curves can be derived based on SAE service break maximum stopping distances 9
- 10. Stopping Distance Characteristics For example, stopping distance characteristics of vehicles of 200,000 to 400,000 pounds GVW 10
- 11. Stopping Distances • Priorto final road layout, manufacturers of vehicles that will use the road should be contacted to verify the service brake performance capabilities 11
- 12. Vertical Alignment • Establishment of grades and vertical curves that allow adequate stopping distances on all segments of the haul road • Maximum sustained grades • Reduction in grade significantly increases vehicle uphill speed • Reduction in grade decreases cycle time, fuel consumption, stress on mechanical components and operating costs • Reduction in grade increases safe descent speeds, increasing cycle time • The benefits of low grades offset by construction costs associated with low grades 12
- 13.
- 14.
- 15. Vertical Alignment • Maximumsustained 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 construction consideration 15
- 16. Vertical Alignment • Maximumsustained 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 determination of the appropriate grades 16
- 17. Vertical Curves • Verticalcurves 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 eye height (usually minimum height for articulated haulage trucks of 200,000 to 400,000 pound of GVW) 18
- 19. Horizontal Alignment • Dealsprimarily with design of curves and considers previously discussed radius, width, and sight distance in addition to superelevation • Cross slopes also should be considered in the design 19
- 20. Curves, Superelevation, and Speed Limits • Superelevation grade recommendations vary but should be limited to 10% or less because of traction limitations • Depending on magnitude of the side friction forces at low speed, different values are suggested for small radius curves • Kaufman and Ault suggest .04-.06 fpf (basically the normal cross slope) 20
- 21. Curves, Superelevation, and Speed 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 21
- 22.
- 23. Recommended Superelevation Rates Ifsuperelevation is not used, speed limits should be set on curves. 23
- 24. Curves, Superelevation, and Speed 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 24
- 25. Combinations of Alignments •Avoid sharp horizontal curvature at or near the crest of a hill • Avoid sharp horizontal curves near the bottom of sustained downgrades • Avoid intersections near crest verticals and sharp horizontal curvatures • Intersections should be made flat as possible • If passing allowed, grades should be constant and long enough 25
- 26. Cross Section • Astable road base is very important • Sufficiently rigid bearing material should be used beneath the surface • Define the bearing capacity of the material using the California Bearing Ratio (CBR) 26
- 27.
- 28.
- 29. Cross Slopes • Crossslopes 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 29
- 30. Cross Slopes • Highercross slopes permit rapid drainage, reduce puddles and saturated sub-base, and are used on rough surfaces (gravel and crushed rock) or where mud and snow are not a problem • High cross slopes can be particularly problematic with ice or snow on high grades (+5%) 30
- 31. Recommended Rate of Cross- Slope Change Slope change should be gradual. 31
- 32. Width • On straightor tangent segments, width depends on • Vehicle width • Number of lanes • Recommended vehicle clearance, which ranges from 44 to 50% of vehicle width 32
- 33. Minimum Road DesignWidths for Various Size Dump Trucks 33
- 34. Typical Design HaulRoad Width Typical design haul- road width for two-way traffic using 77.11-t (85- st) trucks 34
- 35.
- 36. Width • Berm heightand width as a function of vehicle 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 on curves (should be exceeded) 36
- 37. Haulageway Widths onCurves 37
- 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 38
- 39. Berms • Larger bouldersbacked 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 39
- 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 40
- 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 10 mph 20 mph Provision Spacing 1,000 ft 800 ft (Kaufman and Ault) 41
- 42.
- 43. Median Runaway-Vehicle Provision 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 43
- 44. Median Runaway-Vehicle Provision Berms • Requires maintenance in freezing conditions • Agitation to prevent damage to vehicle • May cover berm in high rainfall areas 44
- 45. Escape Lanes • Goodtool 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 45
- 46. Escape Lanes • Lengtha 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 46
- 47. Escape Lanes 47
- 48. Maintenance • The roadsurface is deformed by the constant pounding of haulage vehicles. • A good road maintenance program is necessary for safety and economics. 48
- 49. Safety Considerations • Dust,potholes, ruts, depressions, bumps, and other conditions can impede vehicular control. 49
- 50. Economic Considerations • The wear on every component is increased when a vehicle travels over a rough surface. • If the vehicle brakes constantly, unnecessary lining wear occurs as well. 50
- 51. Dust Control • Dustmay infiltrate brakes, air filters, hydraulic lifts, and other components of machinery. • The abrasive effect of dust will result in costly cleaning or replacement of these items. 51
- 52. Deterioration Factors • Weather •Vehicles follow a similar path • Spillage 52
- 53. Motor Graders • Amotor grader should be used to maintain cross slopes, remove spills, and to fill and smooth surface depressions as they occur. 53
- 54. Road Drainage • Toavoid overflow, roadside ditches and culverts should be periodically cleaned. • Avoid erosion or saturation of subbase materials. 54
- 55.