6 DYNAMIC PROBING TEST (DP)

(1)P This method covers the determination of the resistance of soils and soft rocks in situ to the dynamic penetration of a cone. A hammer of a given mass and falling height is used to drive the cone. The penetration resistance is defined as the number of blows required to drive the penetrometer over a defined distance. A continuous record is provided with respect to depth but no samples are recovered.

(2)P Four procedures are included, covering a wide range of specific work per blow: DPL, DPM, DPH and DPSH.

Dynamic probing light (DPL): test representing the lower end of the mass range of dynamic penetrometers included in this document and defined in table 6.1.
Dynamic probing medium (DPM): test representing the medium mass range of dynamic penetrometers included in this document and defined in table 6.1.
Dynamic probing heavy (DPH): test representing the medium to very heavy mass range of dynamic penetrometers included in this document and defined in table 6.1.
Dynamic probing superheavy (DPSH): test representing the upper end of the mass range of dynamic penetrometers included in this document and defined in table 6.1, closely related to the dimensions of the SPT.

(3) The results of this test are specially suited for the qualitative evaluation of a soil profile or as a relative comparison of other in situ tests. They may also be used for the determination of the strength and deformation properties of soils, generally of the cohesionless type, through appropriate correlations.

(4)P The tests shall be carried out in accordance with a method that complies with the requirements given in this section (see also 1.1, which especially applies to well established national equipment standards of corresponding countries).

(5)P The test method used shall be reported in detail with the test results.

(6) The test method may be reported by reference to a published standard.

(7)P Any deviation from the requirements given below shall be justified and in particular its influence on the results of the test shall be commented upon.

(8) Experience of deviations exists with respect to:

hammer mass: e.g. 63,5 kg instead of the 50 kg specified for the DPH;
falling height;
dimensions of the cone: e.g. an area of 15 cm 2 instead of the 10 cm 2 specified for the DPM.

(9) In locations with special difficulties of accessibility lighter equipment and procedures other than those specified below may be used.

6.2 Definitions

(1)P anvil or drive head: that portion of the drive-weight assembly which the hammer strikes and through which the hammer energy passes into the drive rods.

(2)P cone: pointed probe of standard dimensions used to measure the resistance to penetration (see figure 6.1).

(3)P drive rods: rods that connect the drive-weight assembly to the cone.

(4)P drive-weight assembly: a device consisting of the hammer, hammer fall guide, the anvil and the drop system.

(5)P Energy ratio- ER_r : ratio of the actual energy delivered by the drive-weight assembly into the drive rod, immediately below the anvil, and the theoretical free fall energy of the hammer, expressed in percentage.

(6)P hammer: that portion of the drive-weight assembly which is successively lifted and dropped to provide the energy that accomplishes the penetration of the cone.

(7)P N -values: number of blows required to drive the penetrometer over a defined distance, expressed in cm by the corresponding subindex ( N₁₀ or N₂₀ ).

6.3 Equipment

6.3.1 Cone

(1)P The cone of steel or cast iron shall have an apex angle of 90° and an upper cylindrical extension mantle and transition to the extension rods as shown in Figure 6.1 and with the dimensions and tolerances given in Table 6.1. The cone may be sacrificial or retained for recovery.

Cone for dynamic probing

Figure 6.1: Cone for dynamic probing

6.3.2 Drive rods

(1)P 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. Dimensions and masses of the drive rods are given in table 6.1.

(2) Solid rods may be used, hollow rods should be preferred in order to reduce weight.

Table 6.1: Dimensions and masses for the four types of dynamic probing apparatus

DPL (light)	DPM (medium)	DPH (heavy)	DPSH (super heavy)
Driving device
hammer: mass m (kg) height of fall h (mm) length/diameter ( D_n ) ratio	10 ± 0,1 500 ± 10 ≥ 1 ≤ 2	30 ± 0,3 500 ± 10 ≥ 1 ≤ 2	50 + 0,5 500 ±10 ≥ 1 ≤ 2	63,5 ± 0,5 750 + 20 ≥ 1 ≤ 2
Anvil
diameter, d , (mm) mass (kg) (max.) (guide rod included)	100 < d < 0,5 D_n 6	100 < d < 0,5 D_n 18	100 < d < 0,5 D_n 18	100 < d < 0,5 D_n 30
90 ° Cone
nominal base area A (cm 2 ) base diameter ( D ) new (mm) base diameter, worn (mm) (min.) mantle length (mm) tapper angle upper (deg.) length of cone tip, (mm) tip max. Permissible wear (mm)	10 35,7 ± 0,3

6.3.3 Driving device

(1)P Dimensions and masses of the components of the driving device are given in table 6.1. The following requirements shall be fulfilled:

the steel hammer must be conveniently guided to ensure minimal resistance during the drop;
the 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;
the steel drive head or anvil shall be rigidly connected to the top of the drive rods.

Eurocode 7 Geotechnical design — Part 3: Design assisted by fieldtesting