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Norway

penetration are logged. The lower part of Fig. 2.1 demonstrates the presentation of the results.

FIG.2.1. Weight sounding, penetration diagram s.

The number of half turns per meter of drill penetration is shown to the right side of the diagram (A). The loading is shown to the left on the borehole mark-ing. (B) shows another way of drawing the results. The applied load is shown on the left side of the column. The fuli cross-streak indicates 100 half-turns, and a half cross-streak indicates 25 half-turns as a function of depth.

In this way a morę concentrated drawing of results is obtained. The users of this last type of diagram, have to reoord the penetration resistance as the penetration for each 25 half-turns. When using hand drilling, it is also possible to collect informations by listening to the sound passing through the rods from the point on its way down. If it, for instance, penetrates a sandy layer, a rustling sound can be heard. An experi-enced operator can detact many useful informations which is noted at the bor-ing card. When the drilling string is brought to a stop by rotation, it is recommended practice to blow the rods further down by using a sledge-hammer.

It can be possible to registrate from the blows whether the tip is stopped at hard layers or it touches the bedrock (or a błock).

For several years now the hand drilling has been supplemented by a mechanical device, driven by a smali petrol-motor. Fig. 2.2 illustrates how this device is operated.

FIG.2.2 Mechonicol device for weight sounding.

The amount of half turns pr. 20 cm is counted automatically. The two men have to push down to give a vertical force of 100 kp (the applied force is shown at a weight indicator). The remaining procedurę is the same as described for hand drilling. Some of the human errors may be decreased by using this mechanic-ally operated device, but others may occur, such as influence from the vibrat-ing of the motor. A research program has been carried out at The Norwegian Institute of Technology to clearify if the two methods give the same results.

The borings took place in clay, silt and sand. In short it can be said that the differences observed is of no significa-tion with respect to the generał view of the soil stratum. In the same research program was investigated the influence of crooked rods and worn out tips. The results are used in the proposed Standard for weight sounding.