The use of undisturbed samples to evaluate in situ density and the Standard Penetration Test (SPT) to estimate in situ relative density is reviewed. A procedure for obtaining high-quality undisturbed samples of sands and the influence of this sampling procedure on the in situ relative density are discussed. The use of radiographs to evaluate sample quality is examined.

As a result of studies reviewed, it is concluded that the SPT is not sufficiently accurate to be recommended for final evaluation of the density or relative density of a site unless site specific correlations are developed. High-quality undisturbed samples of sands may be obtained using a fixed-piston sampler and drilling mud. This sampling procedure yields very good samples in deposits of medium-dense sands; however, the procedure tends to density samples of loose sands and loosen samples of dense sands.