Since SE exam covers such a broad topic, pretty much “anything” is possible.

My suggestion:

When you come across something that you are not sure how to do, look to see if it’s mentioned one-way or another in the spec .

If so, you should really figure it out and learn it.

If not, put it in the back-burner and focus on other major items first then come back to it later (But make you sure you do!) It’s a good idea to plan your study schedule and add these items to the end.

In this case of the multiple soil layers, I would probably put it in the back-burner but still make sure I know it before the exam.

Now about the vertical component of active pressure due to back fill:

If this happens on the exam essay portion and the question doesn’t specifically tell you, your best bet is to design it like how you normally would and then state all of your assumptions (e.g. “there is also a vertical component due to active pressure from back fill; however, it’s conservatively not included here because…”) – something like that.

Hope this helps.

Jake, thanks for reading.

Firstly, something I will add to future disclaimers at the article ends is I cannot reveal anything I might have learned regarding the actual exam content per the NCEES non-disclosure agreement and good conscience. I also take steps to ensure that the articles I write do not reflect what was on the exam. Thus, anything I mention above or here is entirely my opinion based on the published NCEES exam specifications, the sample NCEES exam, and my understanding of typical engineering exam questions asked in college, test preparation books, engineering textbooks, and so on.

With that in mind, I think it’s possible that you could have multiple soil layers or saturated soil on an exam question. They seem to fit the concept of the SE exam in testing fundamental structural engineering skills. Any more than that I can’t say, either because I don’t know any more or I do. Try not to read into things like this too much as I have to be purposefully vague.

For your second question I always include that in my design. It’s not a difficult load to calculate and it’s a very real load. Not including it may not always be conservative. For example the increased vertical load could cause bearing pressure issues or require additional reinforcement. However, you are correct that it will depend on soil friction and will generally counteract the overturning moments.

I had the good fortune of being required to write a spreadsheet for retaining wall design in my undergrad Geotech II class. It was a perfect way to learn how each component of design alters the resulting wall. I still use it today to check designs that our software can’t check.

Two thoughts:

Could a question be asked where there are multiple soil layers, or saturated soil, behind the wall? Or have you seen specific information that this would not be asked? It would complicate the design a bit, but maybe could still be a potential question.

It has been a while since I have designed a wall with an inclined backfill grade. When you discuss the vertical component of active earth pressure, do you typically used that value in design? I seem to remember leaving it out as it provides a stabilizing moment to the wall that depends on the frictional resistance of the soil to the back face of the wall.

Thanks again for the great discussion and I look forward to any upcoming articles!