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Norway

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The assumed ąuaternary geological history of the North Sea area, is complex. The glaciers covering $candinavia, had its borderline where the shallow parts of the North Sea starts (over the Norwegian Trench). England was covered by another ice cap. Between these glaciers was formed a separate ice cap, covering the central parts of the North Sea. This glaciers, almost at a stand-still during the glacial period, left behind horisont-al layers of dense sand. But before this North Sea glacier was formed, there was river outlets from the European Continent and England through what later on became the North Sea, leaving behind zones of clay which now is found partly covered by sand. (At the Ekofisk area it is found a corresponding stratification; clay beneath a 20 to 30 meter thick layer of dense sand.) The Norwegian Trench makes a demarkation between the North Sea banks and Norway. This Trench follows our coastline up to Stadt (62° North).

The geological history of the Continental shelf farther north is different from what is said about the North Sea area. This shelf has several times been covered by ice, and the activity of the glacier has brought great sedimentary deposits to the shelf. Coarse materials formed mor-aine deposits. During this ice activity the banks of the Continental shelf was formed. During the last glacial period the sea level was approximately 130 m below the level of to-day. This caused a great erosive activity by waves and streams. On the shallow banks, sand and finer materials were washed out from the sediments. The remaining is a sandmixed stony materiał. The retransported sand is deposited in the slopes along the banks of the shelf. The thickness of this cover varies between approximately a few centimeters up to several meters. The finer materiał was deposited in the trenches between the banks. This is a model which might be applied for the Continental shelf areas north of Stadt (62° N).

In short:

-    Banks not deeper than 150 meters, is covered by washed out moraine mainly gravel and stone. Banks below this depth consists of morain deposits.

-    The slopes of the banks is covered by retransported sand.

-    Deeper parts of the trenches between the banks is covered by clay.

In Fig. 1.1 is shown the results from a geological survey madę by The Continental Shelf Division of The Norwegian Council for Scientific and Industrial Research; concerning a part of the Continental shelf in Northern Norway. (The informa-tions concerning this section is mainly gathered from a paper by cand. real. George H. Maisey:    Kvarta»rgeologiske for-

hold p& kontinentalsokkelen. (Quatemary geological conditions on the Continental shelf.)

FIG. 1.1. Results of geological survey at the Continental shelf.

( Map : The Continental Shelf Division of The Royal Norwegian Council for Scientific and Industrial Research)

2. PENETROMETERS AND TEST PROCEDURES USED IN NORWAY

There are several types of penetrometers in use in Norway. The rotated weight sounding have a traditional application and is still a widely used method. But the need of morę rational mechanized field work, have generated a mechanical sounding eąuipment suited for heavy drilling machines or tractors.

Dynamie sounding and cone penetration sounding are methods used under special conditions.

In many construction works, such as pile-foundations, it is necessary to have informations about the depth of the bed-rock. In common use for this purpose, we have a portable percussion-drill machinę. For a morę accurate determina-tion of bedrock, several types of pneu-matic rock-drills are used. To take care of the corrosion problems dealing with use of Steel piles in marinę clays, a corrosion sound is used. The follow-ing is a review of the eąuipment and procedures used in Norway.

2.1 Rotated weight sounding

The method and the eąuipment is well known in the Scandinavian countries. It is proposed by the Sounding Committees in the respective countries, to stand-ardize the eąuipment and the method.

In Fig. 2.1 the generał layout of the eąuipment is illustrated. It is madę up of 22 mm rods, 1 meter long, screwed together with smooth joints. The lower end of the drill forms a screw point 20 cm long. The drill string is loaded in inereraents up to 100 kg. If no penetration is recorded by this maximum static load,the string is rotated down by hand or machinę. During rotation the number of half turns against 0.2 m