Best compaction specification for MSE Walls

[MSEdesigns]

Which Compaction method is best suitable for specifying the compaction requirements on a Segmental retaining wall reinforced with poliester geogrids. Material specified for the reinforced zone is A-2-4 or better.

 

[BigH]

What do you mean by compaction method - the equipment to use? or the standard to compare the compaction to?

 

[MSEdesigns]

I'm talking about the test. Should I specify 95% Standard or 90% Modified Proctor. What difference it makes on the final compacted material?

 

[casimmons]

This varies with soil type, but 95% standard is roughly equivalent to 90% modified. Just make sure that the compaction and soil type you specifiy will give the soil properties you used for design. It would be a good idea to perform triaxial or direct shear testing to verify this.

 

[jdonville]

MSEdesigns,

The following is from the guide specification for MSE walls with segmental concrete facing elements, as presented in FHWA NHI-00-043:

Backfill shall be compacted to 95 percent of the maximum density as determined by AASHTO T-99, Method C or D (with oversize corrections as outlined in Note 7 of that test). For backfills containing more than 30 percent retained on the 19 mm sieve, a method compaction consisting of at least four passes by a heavy roller shall be used. For applications where spread footings are used to support bridge or other structural loads, the top 1.5 m below the footing elevation should be compacted to 100 percent AASHTO T-99.

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State DOTs that I have worked for (as my "ultimate" client) have their own guide specifications which may or may not contain jurisdiction-specific compaction standards that will likely exceed or regurgitate the guide specs mentioned above. All that I have seen to date, however, incorporate by reference the AASHTO Standard Specifications for Highway Bridges, which in turn incorporates by reference the FHWA publication indicated above. Download a copy of the FHWA guide from

http://www.fhwa.dot.gov/bridge/geopub.htm

Jeff


Jeffrey T. Donville, PE
TTL Associates, Inc.

http://www.ttlassoc.com