Chapter C Cross Section (ANSWERS )

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Chapter CCross Section (ANSWERS )

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EXERCISES
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1. An 800 mm diameter culvert is needed in a 14
m fill. What gauge thickness should be used?
Answer Refer to Figure C-4.5a (page C-20).
Gauge thickness should be 3.5.
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• On a highway with 800 AADT, an embankment is 10 m
  high and could be built at 31 slope or 41
  slope. What is the best solution and why?
• Answer See Section C.5.3.1 3rd paragraph.
• The 41 slope is the best solution provided that
  roadside barriers are not required. The life
  cycle cost for installation, maintenance and
  additional collision cost associated with barrier
  protection exceeds the cost of the additional
  fill material. This has been demonstrated through
  economic analysis.

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• For design of a railway underpass (highway going
  under), is a 4.9 m clearance acceptable?
• Answer See Figure C-9.3.2 Clearance Box for
  Railway Underpass
• No. 4.9m is less than the minimum for highways
  (exceptions are sometimes allowed on local roads).

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4.a) Is a barrier warranted? Information
provided Design Speed 110 km/h Embankment
sideslope 4H1V AADT 4,500 vpd Embankment
height 7m Show your work. Answer No. See
Figure C-5.3.1a. b) A 200mm diameter tree is
located 9m from the edge of the driving lane. Is
the tree considered a hazard? Why or why not?
Answer Yes. If the diameter gt 100 mm it is
considered a hazard. (Roadside Design Guide,
November 2007).
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5. Determine the desirable clear zone distance on
a horizontal curve? Information provided Design
Speed 70 km/h Sideslope 4H1V AADT 1,200
vpd Horizontal Radius 700 m Answer See Table
C.5.2a and b. 5m - 6m on inside of curve and 5.5m
- 6.6m on outside.
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• 6. Based on ATs policy- provide a wide subgrade
  to allow for two future overlays (typical 80 mm
  each). On new construction projects, what
  subgrade width is required?
• Information provided
• - Granular base course (GBC) depth 280 mm
• - First stage (lift) ACP depth 70 mm
• Final stage (lift) ACP depth 90 mm
• Two future overlays 160 mm
• Answer Total depth 600 mm.
• a) RAU-211-110 ? 11m 0.6 x 2 x 5 17m
• b) RAD-212.4-120 ? 12.4m 0.6 x 2 x 5 18.4m
• RCU -209 -110 ? 9m 0.6 x 2 x 4 13.8 m
• See Figures CB6-3.50M5, CB6-3.50M6.

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EXERCISES
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• 7. Based on ATs policy- provide a wide subgrade
  to allow for two future overlays (typical 80 mm
  each). On grade widening projects, what subgrade
  width is required per side?
• Information provided
• - Granular base course (GBC) depth 300 mm
• - First stage (lift) ACP depth 40 mm
• Final stage (lift) ACP depth 60 mm
• Two Future overlays 160 mm
• Answer Total depth 560 mm
• Existing RCU-208-110 grade widen to an
• RAU-211-110 ?
• (11m - 8m)/2 (5 x 0.560 ) 4.30 m per side.

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Z 5 (T0.16m)
Grade Widening