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Finland

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the same depth where the sounding comes to a stop after the sounding effected by turning has been continued by blows.

This supposition has proved to be rela-tively valid (EKLUND, 1970).

2.5 Needs of futurę development

As far as equipment and sounding procedurę go. Swedish weight sounding has at present been standardized on the national as well as Scandinavian level. However, the method should be developed further so that the sounding results v;ould not be dependent on the driller to the same extent as nowadays is the case. At present, in clarifications connected with weight sounding particular attention ought, nevertheless, to be paid to in-vestigations called for by the interpre-tation of the test results. It should above all be settled which soil layer properties can be determined by rr.eans of the Swedish weight sound in different soils and in which soils Swedish weight sounding is morę suitable than the other sounding methods in cornmon use.

3. Dynamie penetration test

3.1 General

The dynamie penetration test used in Finland can be included among the so-called heavy dynamie penetration tests. The dynamie penetration test is consi-derably less widely used than Swedish weight sounding. Usually the dynamie penetration test is employed to add to Swedish weight soundings in dense and stony soil layers in which the weight sound's penetration is poor.

The Finnish Geotechnical Society has published instructions for procedurę and standards regarding eąuipment also for the dynamie penetration test (Suo-men Geoteknillinen yhdistys 1968). The Finnish dynamie penetration test corre-sponds to the ram sounding method standardized in Sweden "Method B". The use of the dynamie penetration test in accordance with "Method A" is not very extensive for the time being in Finland. For instance the light penetration test used in Central Europę is not used in Finland as a practical device in site investigations.

3.2 Description of method

In the dynamie penetration test rods eąuipped with a bit are driven into the ground by means of a rammer (fig. 5).

Fig. 5. Dynamie penetration test (Swedish ram sounding).

The rammer's mass is 65 kg (- 1,5 kg) and the height of fali 0,60 m. The rammer falls into a driving base fastened to the rods by wedges. The rammer is lifted by machinę by means of Steel cables fastened to the rammer and it is dropped by loosening these same cables. The rods are of Steel of 0 32 mm their length usually being 2,50 m.

A four-cornered detachable bit of the kind shown in fig. 6 is generally used