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Literature or Examples for Slope Compaction Issues

Literature or Examples for Slope Compaction Issues

(OP)
In our industry (O&G), we find ourselves constructing a lot of containment ponds, landfills, and fresh water ponds that all require construction of a low permeability soil barrier, i.e. a clay liner along the interior face of the structure.

We often find ourselves battling the Construction groups of our clients with respect to how the embankments should be constructed. Naturally, we defend a benched construction model on the slopes, where we require compaction to occur parallel to the embankment. We often get push back saying compaction of materials place along the slope (i.e. on the grade, or perpendicular to the crest) is adequate, and greatly reduces time, effort and materials required.

Traditionally, the industry standard for engineered structures where I work has been that at a grade steeper than 5H:1V, then benching is required. Several engineers are endorsing compaction along the slope of the structure at grades as steep as 3H:1V, which obviously our clients like a lot more. I was wondering if anyone has some examples or some literature that discuss the risks of compacting along the slope at grades steeper than 5H:1V, or if someone could comment that the traditional "industry standard" of compacting on slopes no steeper than 5:1 is perhaps misguided and obsolete.

Many thanks in advance

RE: Literature or Examples for Slope Compaction Issues

horizontal lifts with benching into subgrade on anything steeper than 5:1 is a standard adopted by the corps of engineers for levee and dam construction (which is basically what you are constructing). for a long, linear embankment, I don't see how going perpendicular to the alignment could possibly save time. Suggest a test fill to evaluate if adequate compaction is achieved going the other direction. I would assume you will have issues with poor compaction between each vertical strip.

RE: Literature or Examples for Slope Compaction Issues

Do you mean leave the surface benched, or bench the clay liner into the sidewalls with a smooth exposed slope?

RE: Literature or Examples for Slope Compaction Issues

We'd require horizontal compaction and keying into the existing fill at grades steeper than 5H:1V.

Once you get them to compact in horizontal lifts, how will you control the moisture content? There is data from over 40 years ago that informs us that permeability can be influenced by a 1000-fold factor for the same soil, depending on whether it's compacted wet or dry of optimum - the LINE of OPTIMUMS! Which runs parallel to the zero-air-voids curve. So, at 95 percent compaction, that'd mean optimum water content is dry of, "Optimum." I refer you to the work of Mitchell, Hooper and Campenella.

f-d

ípapß gordo ainÆt no madre flaca!

RE: Literature or Examples for Slope Compaction Issues

Landfills (both solid waste and hazardous) are typically built with a 3H:1V slope. EPA has guidance for the landfill design, but many are old (e.g., EPA/625/4-89/O22 Seminar Publication Requirements for Hazardous Waste Landfill Design, Construction and Closure, August 1989)

RE: Literature or Examples for Slope Compaction Issues

For my DoD projects, slopes are recommended to be 3H:1V to allow for mowing equipment.

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