Relative density

Gibbs & Holtz (1957)

•	correlation valid for any effective pressure

•	Dr is underestimated for gravels and over estimated for silts

Skempton (1986)

•	process valid for Normally consolidated silts, sands, and fine to coarse sands at any effective pressure

•	Dr is underestimated for gravels and over estimated for silts

Schultze & Menzenbach (1961)

•	for Normally consolidated fine and gravelly sand

•	method valid for any effective pressure in Normally consolidated deposits

•	Dr is underestimated for gravels and over estimated for silts.