266371448

cedure shall be recorded.

	b)
040 — 45 mm
HOllÓW		SOLID OR
MAX WEIGHT		HOLLOW
akg/m

Fig. 2 Points and rod for dynamie probing DPA (a) and DPB (b).

3. TEST PROCEDURĘ 3.1 General

Criteria for termination of a test should be specified in advance. The depth required will depend on local conditions and the purpose of the particular test.

3.2 Probing eąuipment

The probing shall be done vertically unless specified otherwise. The maximum deviation of the drilling rig is 2%, 1 (horizontal) to 50 (vertical). The probing eąuipment shall be firmly supported. The point and the extension rods must be guided at the begin-ning of a test to keep the rods straight. Pre-boring may be reąuired. The diameter of the borę hole shall be slightly larger than that of the point. The test rig shall be positioned in such a way that the extension rods are not allowed to bend above the ground surface.

3-3 Driving

The ratę shall be 20-60 blows per minutę. (The recommended ratę is 30 blows per minutę.) In cohesive soils the blow ratę shall not exceed 30 blows per minutę. The number of blows shall be recorded every 0.2 m of penetration (see notę 3 para. 6).

The driving shall be continuous as far as possible. Ali interruptions longer than 5 minutes shall be recorded in the site log.

Ali factors which can influence penetration resistance should be checked continuously. Any deviations from the recommended pro-

Rotation of the rods is recommended for the DPA test. When casing is used for the DPA the distance between the point and the bottom of the casing shall be at least 0.3 m and not exceed 1.0 m. The clearance between rod and casing shall be smali at the bottom of the casing. The contact surface with the extension rods shall be smooth to prevent jamming of the rods. It is advantageous to inject fluid or air under pressure between rod and casing to keep the annulus clean.

If drilling mud is used to eliminate friction between the soil and the rod and to stabil-ise the hole, the mud shall be injected through holes in the hollow rods near the point. The holes shall be directed horizon-tally or slightly upwards. The injection pressure shall be sufficient so that the drilling mud fills the annular space between the soil and the rod. The pressure shall not be so high that the fluid is forced out of the borehole (see notę 5).

For the DPB test the rods shall be rotated one fuli turn every metre to keep the hole straight and vertical. When the depth exceeds 10 m the rods shall be rotated every 0.2 m.

It is recommended that the torąue reąuired for rotation is measured and that a mechan-ised rotating device is used when the depth is large.

The extension rods shall be examined after each test to check their straightness.

4. REPORTING OF TEST RESULTS

The following information shall be recorded:

a)    Location of the probing Type of application Purpose of probing Datę of probing

b)    Borehole number, elevation and location of the borehole.

Position of the test rig with respect to the ground surface.

Elevation or depth of the ground water table.

c)    Eąuipment used.

Type of point, rod, casing, drilling fluid, injection pressure, type of test.

d)    Mass of hammer, height of fali and the number of blows reąuired every 0.2 m of penetration.

e)    Elevation or depth where the rods were rotated.

f)    Deviations from the normal procedurę such as interruptions or damage on rods.

g)    Observations madę by the operator such as soil type, sounds in the extension rods, indication of stones, disturbances, etc.

An example of a site log is shown in Fig. 3*

112