Roadway Profile Grade Line 1

[foley7]

I posted a thread earlier about overlaying a roadway with 2 inches of asphalt. After the survey was performed the existing roadway profile grade line is not smooth...after reviewing the existing profile grade the general slope of the road is -0.20% with variable grade breaks that are a couple of tenths and hundreths on 50 ft intervals. When preparing the proposed profile grade is it worth making the profile smooth or just follow the existing profile grade? If the profile is smoothed out is it going to be a construction headache that's not worth the effort?

 

[Drumchaser]

Unless there exist issues with the super elevations with-in the horizontal curves (that require level-up ACP to correct back to acceptable levels) a 2" overlay with todays paving equiptment should improve the riding qualities. The paver runs (in most cases) on a 40ft "ski" or other electronics that improves the profile.
It usually comes down to money, if you have enough funds to include a level-up course this would be even better. Given two oportunities to improve the ride (two courses of ACP) usually allows ruts to be filled, cross-slope to be corrected, much better ride.
Even if you just include enough quantity ($) for leveling up the worst areas of pavement, you should improve the ride substantially.
Without an overall picture of the existing roadway your question is hard to define, generally a 2" overlay should be adequate to imprive the ride.

 

[foley7]

Thanks for the information. Now a construction questions....If the ski follows the existing road grade profile will it pick up some of the dips in the profile? It sounds to me like the 40 ft ski when used will fill some of those dips in???

 

[beej67]

0.20% isn't a lot of grade, and could wreck your gutter spread. It might help your drainage out a lot if you artificially pushed some high and low points into the vertical alignment. That sort of thing is worth looking into early, or at least planning for, so you don't end up needing a lot more inlets because of how you set your vertical alignment.



Hydrology, Drainage Analysis, Flood Studies, and Complex Stormwater Litigation for Atlanta and the South East -

http://www.campbellcivil.com

 

[Boltricity]

Hey foley7,

I'm not sure I completely understand the issue as you describe it. I have some questions:

1. I'm not clear on what you mean by a -0.2% grade. Is this the longitudinal grade along the road centerline profile? Or something else? Does the negative number just mean that it is falling in elevation in the positive (stationing) direction? Or something else?
2. What exists along the edge of the paved roadway? Is it a ditch, or is there some sort of curb or curb/gutter system, where you have to match the grade?
3. If there is a curb or curb/gutter, what is the typical longitudinal grade along the curb and gutter? (It could be different than the centerline profile grade).
4. What is the typical (or range)percent cross-fall on the pavement from centerline to the edge of pavement?
5. Are you aware of any drainage issues/"bird baths" on the existing road pavement?

These things would be helpful to know. I've done a lot of road design/widenings/retrofits where these issues are critical to making final design decisions. I'll try to help out.