6585845037

Norway

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has been found to be too high by using the sounding eąuipment of to-day. Plans are already madę to improve the corrosion sounding method and eąuipment.

FIG.2. U. Corrosion sound point and instrument.

soundings indicate homogeneous ground conditions.

It may be said, there is a deeply rooted scepticism towards the use of penetration soundings as a base for any de-finite foundation design or settlement calculations. Of course, there is a lot of experience gained during many years, especially by using the rotating sound and the ram sound. So the results are commonly used for evaluation of pile length and bearing capacity of piles. This evaluation will always be followed by pile tests carried out in fuli scalę or pile driving observations. There have been carried out some research to find the coherence between penetration resistance and the bearing capacity of different types of piles.

The Norwegian Pile Committee has given recommandations concerning the relation between penetration resistance and the bearing capacity of piles. These recommandations are based on experience, research and observations during field works and load tests. This is the only Norwegian recommandation where penetration resistance is used in connection with any foundation design.

inside diameter    1 3/8"

outside diameter    2”

weight of hammer    140 lb.

falling height    30 in.

2.8 The Standard Penetration Test

The method is well known in Norway, but is only seldom used for sampling and penetration testing in gravel and sandy materials. The specifications of the eąuipment and the field practice follow the reąuirements given by Terzaghi and Peck:

split spoon sampler with

The number of blows, N, necessary to force down the split spoon sampler 30 cm, is recorded. In Norwegian practice is used a 89 mm diam. casing and the sample is taken from the bottom of the casing.

3. INTERPRETATION AND EVALUATION OF TEST RESULTS

The results obtained by penetration sounding have limited application in Norway. Traditionally the sounding are used to get a generał view with respect to depth of bedrock, depth of dense layers, the stratification of the soil and relative density. This soundings are relatively easy and ąuick, especially in our clay deposits, so they are carried out at many spots compared to other borings. The soundings form the base for planning of remaining field works, such as sampling, vane boring and compressometer tests.

The expensive works may hence be limited to a minimum, if the greater number of

3.1 Classification due to penetration resistance

The Norwegian Geotechnical Society has appointed a committee to recommend a presentation of geotechnical investiga-tions. The result of the work of the committee is presented in: "Guidelines for the presentation of geotechnical investigations". In these guidelines is also a chapter which is referred beIow:

"Classification due to penetration resistance.

The result of different types of penetration tests is proposed classified by the penetration resistance according to the table below. It is assumed that the dynamie sounding (ram-sounding) eąuipment shall be used with an extended 40 mm diameter tip (12 cm²), a ram energy (falling weight•falling height) between 25 kgm and 75 kgm, and that the total length of rods into the ground is less than 25 meters. The ram sounding resistance Q is given in the dimension tonmeter/m£ter.

Weight sounding

Penetration resistance		Load kg	Penetration each 25half turns, m	No. of half turns pr. m
Very little resist.		*100		0
Little	•• .	100	>0.7	<35
Medium	tl ,	100	0.2-0.7	35-125
Large	fl „	100	0.1-0.2	125-250
Very large -	tl „	100	<0.1	>250