Soil and Compaction
Soil Classification by Cone Penetration Testing (CPT)
Soil classification by grain size analysis is more precise than any indirect way of soil classification.
However, as CPT sounding becomes more and more popular, this test is used to predict not only the in situ relative density but also the soil type in which the sounding was made.
CPT Soil Classification Diagram after Robertson
Experience of our company with over 500 million m3 of sand and gravel compacted over the past 15 years suggests that three limit lines can be drawn that together define the zone of compactable granular soil indicated by the green box, added to the graph by Robertson et al., 1986 :
Zone Soil Behaviour