The Standard Penetration Test (SPT) value is derived from field measurements utilizing the split-spoon sampler. The split-spoon which is cut into two longitudinal sections is driven into the soil at the bottom of the borehole obtaining representative samples for engineering analysis.  The split-spoon sampler is the most common standard procedure in geotechnical engineering as they recover representative specimens suitable for classification and certain laboratory testing. 

    Continuous sampling is an advanced geotechnical drilling method that retrieves a continuous core of subsurface material, providing detailed insights into soil and rock layers encountered for precise engineering design and construction assessments.

    Thinwall samples are typically used whenever soft cohesive soils with a total blow count of 6 or less is encountered.  This type of sampling is only representative when the material is uniform throughout. Thinwall sampling uses a 30 inch-long, 3 inch diameter tube and is pushed into the material for an undisturbed sample recovery. Thinwall samples are used in very detailed and specialized laboratory test. Thus, they must be treated with extra care. 

    Rock Quality Designation (RQD) is a geotechnical drilling sampling method that assesses the integrity of rock formations by visually inspecting the recovered core, aiding in engineering design and stability assessments.