Variability in Compaction Control

Abstract

A field study was made for evaluation of variability in degree of compaction of structural fills. Multiple runs of field‐density tests were performed at three sites by nine geotechnical engineering firms in San Diego, California. The tests were run after the geotechnical engineer had tested and approved each site as having met the 90% relative compaction requirement. All tests at each site were performed at the same time and at the same elevation in close proximity to each other. A statistical analysis of the results indicated a significant scatter in percent compaction data: The range of variations, expressed as a percentage of the mean value, were about 17% for a uniform silty sand fill, 15% for a silty clay fill, and 26% for a gravelly to cobbly sand fill. This amount of variability in relative compaction is greater than that generally found in embankment dams. This is partly because the standards of practice for mass grading of structural fills are less rigorous than for dams, and partly because of inadequate or imperfect fill‐control procedures.