The Mackintosh Probe development was based on the principles stated by Hvorslev (1948) for drive rods for sounding and sampling and recommended methods for static and dynamic sounding by European Group Subcommittee (1968). The probe consists of a cased screwed onto the lower end of the rod. The rods are of 16mm diameter HY steel each of length 120 cm. The rods are connected to each other by 25 mm outer diameter couplings. These couplings provide the lateral support to the rods so as to prevent buckling during driving. Driving is performed with a small hammer of 5 kg in weight and falling vertically through a fixed height of 30 cm along a guide rod. The total number of blows required for the pointer to penetrate a distance of 30 cm is recorded and used as a measure of the consistency of cohesive soil and the packing of granular soil.

The relationship between Mackintosh Probe and Safe Pressure is as follows: –

P = (2860 + 550 (R – 40)1/2) x 0.04788 kN/m2 (Blow Counts above 40)
P = Refer Chart for blows (Blow Counts below 40)

Where,

P = safe pressure (kN/m2)
R = Mackintosh Probe Penetration resistance in blows/0.3m