Compaction Density Of Residual Soils And Weathered Rock

Burt G Look

Residual soils, weathered rock and overburden quarry fill represent a significant amount of fill used in road embankments. These have a high stone content which affects both the bulk density and the accuracy of the quality tests associated with compaction control. Density is the parameter that one is most likely to have a good estimate. It is used as an input in settlement and slope stability analysis of fills. The assumed density value may become critical for high fills or when embankments are placed on soft and compressible soils. Density testing is widely used in earthworks quality control (QC) and is arguably the parameter with the largest database. Construction records from compacted embankment fills from QC for major construction projects are used to check this most basic and simplest of design assumptions. Observation of commonly used density value in geotechnical investigation and design reports compared with construction records show that industry has a persistent error in analyses for an input that is arguably the easiest and simplest input parameter to determine. Three cases studies are used to illustrate the influence of an assumed density. Two of these cases led to contractual and legal issues as this simple parameter affects quantities placed, settlement and stability analysis.