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friction sleeves located at larger dis-tances from the cone with those obtained with the recommended standard sleeve.

(d)    The influence of the ratę of penetration, possibly related to the measurement of porę water pressures, at several points in the 'end' stress field.

(e)    Study, by means of inclinometers, of the shape taken by string of push-rods.

(f)    The influence of the dimensions of the base on the cone resistance (for the same geometry of the penetrometer tip).

(g)    The influence of the roughness of the cone and the friction sleeve. The influence of covering half of the total sleeve area with special grooves about 1 mm deep and 1 mm wide (as suggested by the Swedish Committee) should be examined.

A. 2 Recommended subjects for research on the dynamie probing test

(a)    The effeciency of the blow can probably be inereased considerably if an appro-priate anvil cushion is used. This could decrease the scatter of the results and improve the interpretation of the results. Suitable cushions should be tested out in different soil types.

(b)    In the DPB test, friction along the rods can be reduced by using casing, drilling mud, compressed air, rotation of the rods or by using couplings of a slightly larger diameter than that of the rods. Such techniques may facilitate the DPB test and improve the test results. A study should be madę of the skin friction resistance by measuring the torąue when the rods are rotated. Comparisons should be madę between DPA and DPB tests under the same conditions.

(c)    Development of methods to measure in situ the point resistance in the DPB test. This can be done directly at the point or indirectly by studying at the surface the reflected stress wave.

(d)    The relationship between the dynamie point resistance, the static point resistance and the bearing capacity of piles.

(e)    The relationship between dynamie point resistance, SPT and piąte bearing capacity. The influence of the ground water table should be examined.

(f)    The limitations of different dynamie tests.

(g)    Different light and heavy dynamie penetration tests should be compared and evaluated under identical conditions before standardization of these methods.

tained with a self-tripping mechanism and friction winches.

(b)    A comparative study of the N values obtained with a self-tripping mechanism operating at the top of the borehole and down-the-hole drive weight assembly.

(c)    For the interpretation of the SPT test, various authors have published correction factors to be applied to the design rec-ommendations published by K Terzaghi and R B Peck, 'Soil Mechanics in Engineering Practice' 19^8- Are these correction factors based on data obtained from a self-tripping mechanism or friction winch?

(d)    A Comparative study of the N values obtained with the recommended standard SPT and the SPT (cone) apparatus.

(e)    A comparative study of different 'standard' rods at different depths to assess the effect of rod stiffness on the N value.

(f)    The effect on the N value of the diameter of the borehole.

(g)    The effect on the N value of the State of stress at the test location.

Recommended subjects for research on the weight sounding test

(a)    A comparative study of the weight sounding test and other penetration tests in order to get correlations for different soils.

(b)    The relationship between the penetration resistance and the bearing capacity and the settlements of spread footings and piles.

(c)    The allowable limit of wear on the lower pyramidal part of the point.

Respectfully submitted:

H	Zweck	FRG (chairman)
F	Baguelin	France
E	de Beer	Belgium
B	Broms	Sweden
W	Heijnen	Netherlands
s	Rodin	UK
E	Schultze	FRG
G	Stefanoff	Bułgaria
Y	Trofimenkov	USSR
U	Bergdahl	Sweden (secretary)

^.3 Recommended subjects for research on the SPT test

(a) A comparative study of the N values ob-

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