What are the Geotechnical consideration for road design?

Question

can you guys gimme some hints?urgent help for assignments
thanks

Answer 1

First, you need to consider how the road is used. If you expect a lot of truck traffic, the pavement section will need to be stronger than if you are designing a local side-street that will only get car traffic.

Next, you'd be concerned with the type of soils you have on site. If the soils are gravelly or sandy, your pavement section will probably be able to be thinner. Borings would be best, but excavating some test pits would be OK, too. If your site soils are fine-grained (silts or clays), you can expect to building a thicker pavement section. From my experience, geotextiles and geogrids can do a lot to improve the subgrade so that less over-excavation is required.

Also, depending on the soils, groundwater may be an issue. If you have a well-draining subgrade soil, it wouldn't be as critical. But, if you have a clay or silt subgrade, a drainage layer in your pavement may be a good idea.

I was a resident engineer on a bridge/road construction project for a pretty busy local road that did get quite a bit of truck traffic. The town the project was located in was notorious for having bad subgrade soils (almost all clay, the town used to be one of the largest clay brick manufacturing centers in America years ago). Our pavement section was geotextile, 6" of stone for drainage, another layer of geotextile, 8" of dense-graded aggregate and 10 inches of hot-mix asphalts. And this was the final section we used because we had to build our way up to it by trial and error.

The best thing you can do to ensure good pavement construction, from my experience, is to proof roll the subgrade and any base courses you may have with a fully-loaded tandem truck. When those things are loaded, they will rip up any sub-par soils.

As far as designing a pavement section, most authorities (local, county, state, etc.) will have guidelines or sections that they use for all their work.

Hope this helps.