4 Equipment

4.1 Driving device

Dimensions and masses of the components of the driving device are given in Table 1. The following requirements shall be fulfilled:

  • a) hammer shall be conveniently guided to ensure minimal resistance during the fall;
  • b) automatic release mechanism shall ensure a constant free fall, with a negligible speed of the hammer when released and no induced parasitic movements in the drive rods;
  • c) steel drive head or anvil should be rigidly connected to the top of the drive rods. A loose connection can be chosen;
  • d) guide to provide verticality and lateral support for that part of the string of rods protruding above the ground should be part of the driving device.

If a pneumatic system for lifting a hammer is used, it shall be supplied with inspection documents as stipulated by EN 10204 because the driving energy is not always ensured.

4.2 Anvil

The anvil shall be made of high strength steel. A damper or cushion may be fitted between the hammer and anvil.

4.3 Cone

The cone of steel shall have an apex angle of 90° and an upper cylindrical extension mantle and transition to the extension rods as shown in Figure 1 and with the dimensions and tolerances given in Table 1. The cone may be either retained (fixed) for recovery or disposable (lost). When using a disposable cone the end of the drive rod shall fit tightly into the cone. Alternative specifications for the cones are given in Figure 1.

Cone Type 1 shown as retained Cone Type 2 shown as disposable
a) Cone Type 1 shown as retained (fixed)

b) Cone Type 2 shown as disposable (lost)


  • 1 Extension rod
  • 2 Injection hole (optional)
  • 3 Thread mounting
  • 4 Cone tip
  • 5 Cone
  • 6 Mantle
  • 7 Point mounting
  • L Mantle length
  • D Base diameter
  • dr Rod diameter
Figure 1 — Alternative forms of cones for dynamic probing (for L, D and dr see Table 1)

4.4 Drive rods

The rod material shall be of a high-strength steel with the appropriate characteristics for the work to be performed without excessive deformations and wear. The rods shall be flush jointed, shall be straight and may have spanner flats. Deformations shall be capable of being corrected. The deflection at the mid point of an extension rod measured from a straight line through the ends shall not exceed 1 in 1 000, i.e. 1 mm in 1 m. Dimensions and masses of the drive rods are given in Table 1.

Hollow rods should be used.

4.5 Torque measuring device

The torque necessary to turn the driving rods is measured by means of a torque wrench or similar measuring device. The apparatus shall be able to measure a torque of at least 200 Nm and be graduated to read at least in 5 Nm increments.

A sensor for recording the torque may be used.

The spanner flat in the drive rods can be used to fix the torque wrench or measuring device.

4.6 Optional equipment

4.6.1 Blow counter

A device to count the number of blows of the hammer by measuring mechanical or electric impulses can be placed on the system.

4.6.2 Penetration length measuring device

The penetration length is measured either by counting on a scale on the rods or by recording sensors. In this latter case, resolution shall be better than 1/100 of the measure length.

4.6.3 Injection system

The injection system includes:

  • hollow rods;
  • solid end of the lowest when using disposable (lost} cone;
  • pump with mud connected to a device fixed under the anvil and intended to ensure the filling of the annular space between the ground and the drive rods created by the enlarged cone.

The flow of the pump is such that it will always ensure that the annular space between the ground and the drive rods is filled.

NOTE 1 Mud, for example, can be a mixture of bentonite and water with a mass ratio of dry particles and water of 5 % to 10 %.

NOTE 2 The mud circulation towards the surface is not obligatory. The pressure of injection is that corresponding, after deduction of the head losses, to the hydrostatic pressure due to mud on the level of the cone.

A manual pump may be used.

4.6.4 Apparatus for measuring the dimensions of the cone

The measurement of the diameter and length of the cone is made by means of a slide calliper to the 1/10 of mm or by an equivalent system.

4.6.5 Device to control rod string deviation from the vertical

A system or guide for supporting the protruding part of the rods should be in place to ensure and check that the drive rods are maintained in a vertical alignment.

Table 1 — Dimensions and masses for the four types of dynamic probing apparatus
Dynamic Probing Apparatus Sym­bol Unit DPL (light) DPM
DPSH (super heavy)
Driving device
hammer mass, new
height of fall
500 ± 10
30 ± 0,3
500 ± 10
50 + 0,5
500 ±10
63,5 ± 0,5
500 ± 10
63,5 ± 0,5
750 ± 20
mass (max.)
(guide rod included)
50 < d < Dha
50 < d < Dha
50 < d < 0,5Dha
50 < d < 0,5Dha
50 < d < 0,5Dha 30
90° Cone              
nominal base area A cm 10 15 15 16 20
base diameter, new D mm 35,7 ± 0,3 43,7 ± 0,3 43,7 ±0,3 45,0+ 0,3 50,5 + 0,5
base diameter, worn (min.)   mm 34 42 42 43 49
mantle length (mm) L mm 35,7 ± 1 43,7 ± 1 43,7 ± 1 90,0 ± 2 b 51 ±2
length of cone tip   mm 17,9±0,1 21,9 ± 0,1 21,9 ±0,1 22,5 ± 0,1 25,3 ± 0,4
tip max. permissible wear   mm 3 4 4 5 5
Drive rodsc              
mass (max) m kg/m 3 6 6 6 8
diameter OD (max) dr mm 22 32 32 32 35
rod deviation d:              
lowermost 5 m   % 0,1 0,1 0,1 0,1 0,1
remainder   % 0,2 0,2 0,2 0,2 0,2
Specific work per blow mgh/A kJ/m2 50 100 167 194 238
a Dh diameter of the hammer, in case of rectangular shape, the smaller dimension is assumed to be equivalent to the diameter.
b disposable cone only
c maximum rod length shall not exceed 2 m
d rod deviation from the vertical
NOTE Tolerances given are manufacturing tolerances.

ISO 22476-2:2005 Field testing — Part 2: Dynamic probing