The whole topic of earthwork and compaction is one whose coverage is inconsistent, to say the least, in basic geotechnical publications. Some do a very good job, others ignore it altogether. NAVFAC DM 7.2 has done a very thorough job on the subject, covering topics which are scarce in other places. Compaction is the oldest earth improvement technique we have and is still the most commonly used on construction sites around the world.
There are many topics which are explored in this chapter; I will only mention a few of them. It’s hard to distill all of the information in the book; you’ll just have to get it and find out for yourself. Some of them (such as compaction equipment types and sample fill specifications) are carried over and expanded from the previous document; others are new.
Line of Optimums Method
When I was first brought on board to Soils in Construction, I learned about this, which I discuss in this post (illustration of the method is at the right.) There were few references on the subject to be found, which made Soils in Construction somewhat unique. (I need to say kudos to my co-author, Lee Schroeder, especially for the part of the book on compaction.) We actually got thumbs up during the review process for including it. This edition of NAVFAC DM 7.2 has fixed that lacuna with a section on the subject. I don’t see how one can actually specify a compaction method without it, especially if experience is lacking and/or the soils are variable on a site. They have included information on the effects of “dry of optimum” (left of line 6 on the chart above) and “wet of optimum (right of line 6) as well. All in all, a very nice treatment on the subject.
Making the Cut with Borrow and Fill Calculations
Another topic covered in Soils in Construction is that of borrow and fill calculations. Some soil mechanics books cover this, some don’t. It’s covered in detail in NAVFAC DM 7.2. It will definitely help you to “make the cut” when excavating, transporting, placing and compacting fill materials.
Hydraulic Fills
Many geotechical references treat hydraulic fills as a thing of the past after some early disasters involving them. Evidently not; there is a whole chapter on the subject, both for understanding dams built in this way and for underwater fills, when hydraulic fills are virtually unavoidable.
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