đź•‘ Reading time: 1 minute
A wide range of dynamic and static penetrometers are available, with different types being used in different conditions of sub-strata materials. However, the objective of all probing is the same, namely to provide a profile of penetration resistance with depth, in order to give an assessment of the variability of in-situ materials on site. Probing is carried out rapidly, with simple equipment. It produces simple results, in terms of blows per unit depth of penetration, which are generally plotted as blow-count/depth graphs.
One of the most common types of probing is Mackintosh Probe. The Mackintosh prospecting tool consists of rods which can be threaded together with barrel connectors and which are normally fitted with a driving point at their base, and a light hand-operated driving hammer at their top. The tool provides a very economical method of determining the thickness of soft deposits such as peat. The driving point is streamlined in longitudinal section with a maximum diameter of 27mm. The drive hammer has a total weight of about 4kg. The rods are 1.2m long and 12mm dia. The device is often used to provide a depth profile by driving the point and rods into the ground with equal blows of the full drop height available from the hammer: the number of blows for each 150mm of penetration is recorded. When small pockets of stiff clay are to be penetrated, an auger or a core tube can be substituted for the driving point. The rods can be rotated clockwise at ground level by using a box spanner and tommy bar. Tools can be pushed into or pulled out of the soil using a lifting/driving tool. Because of the light hammer weight the Mackintosh probe is limited in the depths and materials it can penetrate (Clayton C.R.I., Matthews M.C. and Simons N.E., 1995).
