DPSH vs SPT

Soil probing and exploration rigs like the GRIZZLY are designed for Dynamic Probing, which is an alternative to the Standard Penetration Test (SPT).

Standard Penetration Test (SPT) is an in-situ dynamic penetration test to provide information on the properties of soil. It may also collect a disturbed soil sample for grain-size analysis and soil classification. SPT involves the driving of a standard sampler through a distance of 450mm into the bottom of a borehole using the standard weight of 63.5kg falling through 760mm.

Like the SPT, the Dynamic Probing Super Heavy (DPSH) uses a hammer that delivers energy to a rod string by dropping a weight of 63.5kg from a height of 760mm. Unlike the SPT, a solid cone is driven instead of a split spoon sampler. Soil samples are not brought to the surface so a continuos record of penetration is recorded without tripping tool strings in and out of the borehole being evaluated. The International Society for Soil Mechanics and Foundation Engineering (ISSMFE) has outlined a procedure called Dynamic Probing Super Heavy (DPSH) which is designed to closely simulate the dimensions of the Standard Penetration Test (SPT).

A crew size of one and the increased mobility of the GRIZZLY soil probing rig compared favorably with the larger SPT drilling rigs.

Dynamic Probing has many applications. For instance, it may be used to estimate the depths of the interface between hard and soft strata and to trace the outline of objects buried underground. However, the main use of dynamic probing is to interpolate information between boreholes/trial pits swiftly and to supplement information found from boreholes and trial pits at a low cost. For instance, dynamic probing is carried out close to a borehole where the underground conditions are identified. As such, by using the dynamic probing, the result of borehole can be extended to other areas in between two boreholes.