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Published byElaine Jane Underwood Modified over 9 years ago
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Surface Drainage Crown (flat A shape) c Dirt & Gravel: 1/2” - 3/4” per foot (4 - 6 inches in 10 feet)
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Surface Drainage Superelevated Roadway (Curves) Dirt & Gravel: 1/2” - 3/4” min. per foot
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Surface Drainage - Shoulders Flush with road Avoid “shoulder drop – off” Slightly steeper cross slope Avoid secondary ditches Supports roadway Allows water to flow further away from road
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Drainage Systems c c Wrong Right Crown Surface Material Ditch Shoulder Subgrade Base Surface Material Subgrade Base
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Subsurface Drainage Free draining road base beneath the surface Collector systems comprised of perforated pipe surrounded by well- graded aggregate with an outlet pipe or other prefabricated systems
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Subdrains Road Shoulder SubdrainWell-graded aggregate Perforated Pipe Cut or Fill Sections
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3 Most Important Items in Road Maintenance Drainage
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Road Materials Durability (Hardness) Soundness pH (acidity/alkalinity)
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Road Aggregates Granular Well Graded (8 – 15% fines) Free of Vegetation Angular / Irregular (Source) Crushed Not rounded
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Basic Road Maintenance Create a good hard crust surface with a proper cross slope (crown)
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Basic Road Maintenance Blading or smoothing Grading or reshaping Adding new material Transitions
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Basic Road Maintenance All work should be done when some moisture is present Need moisture for proper compaction Avoids dust
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Blading or Smoothing Use grader or drag Mold board tilted forward Light down pressure 30 to 45 degree angle on moldboard 10 to 15 degree tilt on front wheels 3 to 5 miles an hour
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Grading or Reshaping Moldboard tilted backward Sufficient down pressure to produce cutting action 4 passes minimum Windrow & spread each lane Check cross slope Compact
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Adding New Material Scarify existing surface Spread new material Blend old and new material & establish cross slope Compact
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Transitions Road Intersections Driveways Curves Railroad Crossings Bridges
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Road Intersections Gradually eliminate crown 50 to 100 feet from intersection Be sure shoulders have cross slope at point of intersection Do not spread aggregate on paved road
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Driveways Grade to driveway Grade low point at ditchline Do not leave windrow across driveway
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Curves Transition crown to superelevation (and vice versa) within 100 feet of curves 100 50 25 0
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Railroad Crossings Gradually eliminate crown on both sides Do not blade aggregate onto rails Brush off loose aggregate
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Bridges If bridge has crown, maintain on road If not, gradually eliminate crown Road approaches to bridge may need more frequent attention
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Maintenance Frequency Depends on: Road Type Drainage Weather Traffic Volumes Special Events “As Needed!”
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The Professional Operator Knows good techniques & practices Knows his equipment Notices and records other problems that need to be taken care of
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