The Shelby tube is designed to take undisturbed samples in cohesive type soils. Shelby tubes are the preferred method of sampling cohesive soils when using HSA.
Like Shelby Sampler a Piston Sampler is used to sample cohesive soils.
The difference being is a Piston Sampler can be used in an open borehole with Slouph. The sampler is advanced to desired depth, then the tube is advanced with water pressure, into the undisturbed soil.