A standard penetration test (SPT) is an internal dynamic penetration test designed to provide information on soil properties, while also collecting rough soil samples for grain size analysis and soil classification. go
The Cone Penetration Test (CPT) is performed using an instrumented probe with a conical tip, which is hydraulically pushed into the soil at a constant rate. A basic CPT instrument reports tip resistance and shear resistance with a cylindrical barrel. CPT data is correlated with soil properties. Sometimes, tools other than the basic CPT probe are used, including:CPTu – piezocone penetrometer: This probe is advanced using the same equipment as a regular CPT probe, but the probe has an additional instrument that measures the groundwater pressure as the probe is advanced.
SCPTu – seismic piezocone penetrometer: This probe is advanced using the same equipment as a CPT or CPTu probe, but the probe is also equipped with either geophones or accelerometers to detect shear waves and/or pressure waves produced by a source at the surface.
Full flow penetrometers – T-bar, ball and plate: These probes are used in extremely soft clay soils (such as seafloor deposits) and are advanced in the same manner as the CPT. As their names imply, the T-bar is a cylindrical bar attached at right angles to the drill string forming what look likes a T, the ball is a large sphere and the plate is a flat circular plate. In soft clays, soil flows around the probe similar to a viscous fluid. The pressure due to overburdened stress and pore water pressure is equal on all sides of the probes (unlike with CPTs), so no correction is necessary, reducing the source of error and increasing accuracy. It is especially desired in soft soils due to the very low loads on the measuring sensors. Full flow probes can also be cycled up and down to measure remoulded soil resistance. Ultimately, the geotechnical professional can use the measured penetration resistance to estimate undrained and remoulded shear strengths.
Flat plate dilatometer test (DMT) is a flat plate probe often advanced using CPT rigs, but can also be advanced from conventional drill rigs. A diaphragm on the plate applies a lateral force to the soil materials and measures the strain induced for various levels of applied stress at the desired depth interval.
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