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Dynamically driven tube samples are usually obtained at selected intervals in the borings using the ASTM D1586 procedure. In many cases, 2 inch outside diameter samplers are used to obtain the standard penetration resistance.
Undisturbed samples of firmer soils are often obtained with a 3 inch outside diameter. samplers lined with brass rings. The driving impulse is generally recorded as the number of blows of a 140 pound hammer, with a 30 inch free fall drop, for every foot of penetration.
In stratified soils, driving resistance is sometimes recorded in 2 or 3 inch increments so that soil changes and the presence of scattered gravel or cemented layers can be readily detected and more accurate penetration values can be obtained for consideration in design.
Sampling of softer soils is sometimes performed with thin-walled Shelby tubes (ASTM D1587). Tube samples are labeled and placed in watertight containers to maintain field moisture contents for testing.