Sheet pile wall analysis using NAVFAC 7.02 1

[pelelo]

Engineers,

I am working on the design of a sheet pile wall system. The guidelines I am using are the ones provided by NAFVAC DM 7.02.

In Figure 21 (pag 7.2-92), there is a solved example. Please refer to the file attached.

In the safety factor against Failure section (top right column), (taking moments about point A), I noticed that in the sum of moments of active forces, force Pa1 (=1.55 kips and arm of 0.73 ft, acting counterclockwise) is not acting in the same direction as the rest of the active forces (clockwise), but still, for this example it was considered as having the same sign convention as the other active forces acting about this point.

Does this approach by the DM make sense to you?

Another question, Fig 18 (pag 7.2-88) of the same manual, provides instructions of how to compute the embedment depth and the pull out force. In step 2, when computing moments about point a, in order to find the embedment depth, I noticed that the manual suggests to use PP/FS, similar to step 3, for computing the Pull out force. In the example presented in page 7.2-92, this approach is not followed.

PP/FS is only applied when computing anchor pull out force BUT is not applied when computing embedment force.

Please let me know your thoughts.

Thanks.

 

[DanMcGrew]

The NAVFAC example is a typical embedment depth problem using the Free Earth method. The Free Earth method calculates the embedment depth by summing moments around the lowest support. The Factor of Safety method used in the example is very old. Usually today for ASD design the Passive Pressure is divided by 1.5, moments are summed to zero around Point A, then the support force can be calculated by summing the forces in the x direction. The reported embedment depth is the depth calculated above multiplied by 1.2.
For a great example see the NY DOT GDP-11 Revision 4 document dated Aug 2015, Pg E-3 "EXAMPLE-ANCHORED SHEETING WALL". I have attached the document.