Grading sites/road in "non-Florida"

[gjeppesen]

I'm an engineer in SW Florida where everything is flat, flat, flat. Every job requires fill. I think I've worked on one project in 10 years that had a cut.

I spent this past weekend in the GA mountains and marveled at the site engineering involved in sites that weren't flat like I'm used to.

Can someone just give me a rundown on how you go about designing/grading a site, road, etc. in these areas? For example these private drives/roads that serve mountain homes: how do you go about designing the road grades? The're all cut into mountain sides. I know you try to balance cut and fill, but how much time and iterations does it take to get it finalized?

 

[Hoagie]

Hillside grading can be very tricky.

Offhaul is typical for hillside, so forget trying to balance the site.

I'm not sure what code they use in GA----but rest assured that you will likely need to place a bond a/o benching for larger-sized fills (over 15-ft).

Regarding grade, check with the local fire marshall for max grade and turn-around/bypass issues--12% is code, but some juridications will allow you to go steeper, conditionally.

As for slope grading, the soil's report will suggest a max grade for fill/cuts-- typically its 2:1, but I've seen steeper in cases where the material is considered competent by the geo-types.

As for the design process: it's iterative and ultimately dependent upon generating accurate cross-sections. Be sure to get good topo. Lastly: try to reduce or eliminate the need for retaining walls.

I hope this helps.

H.

 

[civilman72]

Hoagie stated a lot of my thoughts, here's some others:

1. Main road grades and location are often driven by the developer's most desirable building site locations. Usually on the uphill and downhill sides of the road, so making sure you can maintain reasonable driveway grades to these building sites from the main road is very often the driving force in the design of the main road.

2. In order to try to balance the roadway as much as possible we would usually go through a few iterations, but with LDD, each iteration was very time-consuming, so we were limited in how many iterations we could complete and still keep in budget. Now that we've started using Civil 3D, I have found much greater success in completing multiple iterations, and truly optimizing the road design and earthwork quantities in record time.

3. Due to the excessive cuts and fills required to construct these roads, very often retaining walls are more economically feasible than maintaining a 2:1 or 3:1 sideslope.