Reference(s):

FHWA (2004)
Rogbeck et al. (2003)
Schaefer et al. (2017)

Method Summary

Density testing of the LTP soil and embankment fill should be performed by nuclear gauge, sand cone, balloon densometer, or other method. The density test method used should be selected based on the fill material; for example, nuclear gauge testing is not recommended in gravel layers. The density test results are then compared with the specified relative compaction from Proctor tests or relative density from minimum and maximum density tests. The moisture content can also be checked while the density testing is performed. The gradation of the material should be verified by submittal from the contractor with recent test results from an independent laboratory. Samples can also be taken from the site and verified by the owner/agency or at the contractor’s expense, if specified in the contract documents. In some cases, triaxial or direct shear testing may be performed to determine the shear strength of the fill material(s).

According to Rogbeck et al. (2003), the load transfer platform and embankment fill should be tested in the field for moisture content and dry density. Field tests or laboratory analysis of fill material shear strength is also recommended.

A lift thickness may be specified. Schaefer et al. (2017) recommends a maximum uncompacted thickness per lift of 250 mm (10 in.) for heavy compaction equipment and a maximum uncompacted thickness per lift of 150 mm (6 in.) for hand-operated equipment.

According to FHWA (2004), LTP fill should be compacted to 95% modified proctor (ASTM D1557) at a moisture content no more than 2% above or below optimum. The test method, frequency, and verification of material specifications and compaction should be stated in the specifications.