Max grade for heavy load on aggregate surface

[jhussus]

I am working on a project outside of the US that will bring a 30 ton load on a tractor trailer up a mountainous area. There is a section where the existing grade is 19% for a distance of 75'. We were thinking of knocking the slope down by bringing in fill (excavating is not an option because of hard rock and equipment that can not remove it). We can make it 12% for 360'. Is 12% still too high? Is 19% for a distance of 75' an issue that needs to be corrected? Any help would be much appreciated. Thanks!

 

[Ron]

Are you concerned about the grade for the sake of the equipment or from an aggregate displacement standpoint? If for aggregate displacement....displacement will occur at all grades, including flat.

 

[jhussus]

I am concerned for the grade just for the sake that it can make it up the hill. This is really going to be a one time use thing, so I'm not concerned if the road gets damaged in the process.

 

[MiketheEngineer]

How about going down?? If you have to with that load - you need a kamikaze pilot.

 

[jhussus]

Taking the load up and leaving it there.

 

[francesca]

The Green Book has a nice chart showing you the tractor-trailer speed drop-off with grade and length. I would think that 19% for 75 ft is better than 12% for 360 ft, but that's a guess. You should look up the table.

 

[Ron]

Traction is a problem on gravel with 19% grade, up or down. Going down, assuming the vehicle is articulated, could be a jacknifing danger.

Not sure of the length of the vehicle you are using, but if typical tractor-trailer, it will be about 55 to 60 feet long. Could be a real problem with transition slopes as well.

 

[jhussus]

I'll have to check out the green book. I don't do a lot of road work so I forget about that book from time to time.

 

[bradleyelwood]

19 percent is about the steepest logging road I have ever seen and if you actually drive it or walk it you will swear it is a lot more than that.

I would suggest you talk to the trucking company and get a crawler tractor for assist, even if you change the grade.