6585845017

Finland

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ness is to use of piston percussion drilling.

1.3    Coarse-grained soils

In Finland coarse-grained soils (gravel, sand) are mainly to be found in eskers, deltas and shore deposits. A wide va-riation can be observed in the thickness of sand deposits. Gravels and sands make up about 5...10 % of Finland*s area.

The gravels are often stony and this brings about the same difficulties when using Swedish weight sound as was the case with moraine. For this reason the dynamie penetration test and the piston percussion drilling are best adapted to work in gravelly soil.

Sand is morę advantageous when using va-rious penetrating tests, although the density of sand slows up and hampers the sounding. There is very little of loose and poorly graded dune sand in Finland. Swedish weight sounding is most commonly used in sandy soils. The dynamie penetration test is used to some degree to determine the density of sand deposits.

1.4    Fine-grained soils

Fine-grained soils are primarily met with in the Coastal regions of Finland where they, for the most part, are soft clays and organie clays. Sediments of the silty type are found in the inner parts of the country. The thickness of the clays is about 10 m on an average, but in the valleys, in the coastal area, deposits about 50 m thick can be found. Clays and silts are very soft, sińce their shear strength usually is of the order 10...30 kN/m^.

Due to the softness of the sediments the Swedish weight sound is mostly used to determine the thickness of the deposits and the approximate strength. Also the static penetrometer has been used of late in fine-grained soils, but its use has, however, not spread very far as yet.

1.4 Organie soils

Peat deposits constitute about 30 % of Finland*s whole area. The layer thickness is 3...4 m on an average. In the first place weight sounding is employed to determine the thickness of peat deposits.

2. Swedish weight sounding 2.1 General

Swedish weight sounding (fig. 1) has been used in Finland already from the

Fig. 1. Swedish weight sounding.

turn of the 1920*s, being at present the sounding method most commonly used in Finland. The sounding was carried out without any uniform specifications or directives till the year 1968. The sounding itself was also effected in numerous different ways and a variety of sounding eąuipment was used. In 1968 the Finnish Geotechnical Society