Horizontal Curves in a HDD Application

[allaboutsoil]

Hello Folks,

For a project in CA, I am trying to calculate the pullback stresses/loads during an HDD application to determine the pipe thickness. I have designed such a trenchless crossing before, using ASTM F1962 and the book by David Willoughby titled "Horizontal Directional Drilling", however those applications had vertical curves only, i.e. straight runs in plan view. This new project has to have horizontal curves as well and these additional curves will increase the stresses on the pipe.

The references I listed above do not give guidance on how to calculate this additional stress due to horizontal curves. Is it a matter of adding additional bending stress to the total stress? Also, during my extensive online search, I have realized that higher (3 to 4 times the vertical) bending radius is assumed for horizontal curves.

So, I will appreciate any input you may have on the design of horizontal curves in a HDD crossing. Thanks.

 

[dicksewerrat]

Call the HDD equipment manufacturer and the pipe manufacturer. That said, I would do the calcs the same way as your vertical curves. The longer radius should have lower values for the same degree of bending.

Richard A. Cornelius, P.E.

http://WWW.amlinereast.com