6585845038

Norway

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q _f = average cone resistance along ^cr the pile

q = average cone resistance in depth ^p - intervals 5-d above and 3»d below the position of the pile tip. d is the diameter of the pile.

f_f = skin friction depending on the density of the sand, approx. 0.005 in case of medium dense sand (q ⁵⁸ 100 kp/cm²) and in-creasing to 0.01 for very loose sand (q * 25 kp/cra²).

f = factor of point resistance, ^p approx. 0.5

The total skin friction ffQ_cf is assumed to be no less than 1 Mp/cm² , even with a very little cone penetrometer resistance. The point resistance f_pqcp is assumed to be maximum of 100 kf>/cm? , even in case of very dense sand.

If the Standard Penetration Test is used, the number of blows N necessary to force the 2“ diara. split spoon sampler 30 cm into the soil is recorded. It is used a falling weight of 63.5 kp and a falling height of 76 cm. The sampling is per-formed from the bottom of a casing. The empirical relation between cone penetro-raeter resistance and the number of blows from the S.P.T. is:

q_c = 3 - 4•N kp/cm²

This forms the base for calculating the skin friction and the end-bearing capa-city as described aboveV

4. ASPECTS CONCERNING FUTURĘ DEVEL0P-MENT OF TESTING EQUIPMENT AND TESTING METHODS

Norwegian geotechnical firms and institu-tions have been asked to express their views on needs for futurę geotechnical field equipment, especially concerning penetrometers. To summarize the differ-ent statement, it may be said that there is a generał contentment with the avail-able equipment of to-day. But it was also stated that the process of mechaniz-ing the equipment ought to be continued.

We have relatively few types of penetrometers, and their applicability differs depending on what kind of soil and soil exploration we are dealing with. There is an expressed wish of a generał equip-ment, able to combine different types of sounding. As an example, the drill-pressure sounding is a method well suited for heavy equipment. It would be of great advantage if this method could be combined with the rock control-boring, i.e. using the same rods and tips and doing the soil and rock exploration in the same boring operation, if necessary. The heavy equipment is suited for a majority of jobs, but due to the variable topography of our ground, the light sounding penetrometers will be a very useful and necessary equipment, also in the futurę. Such equipment may also be improved.

As an example, some research have been done to equip the percussion sound with a device giving a morę definite indica-tion of bedrock.

Over the last years it has also been a tendency towards medium heavy rigs and tractors. In 1973 Geonor A/S has developed an hydraulically operated rig mounted on a four-wheel light tractor.

The equipment is able to carry out main field works such as penetration tests, sampling and vane borings, besides bee-ing well suited to move in difficult terrain.

The futurę penetration tests may well be carried out by light equipment, partly manually operated, or by a medium heavy equipment with a rig sounding and sampling works, and a heavy one suitable for all types of field works.

As mentioned before, the cone resistance penetrometer has had a limited applica-tion in Norway up to now. The equipment is mainly used in connection with pile foundation jobs in friction soil. Dur-ing the last year, some theoretical in-vestigations have been madę by professor Janbu, indicating that it may be possible to find shear strength parameters from cone resistance recordings. If the soil is saturated, it will be necessary also to do a "pore-pressure" sounding. This require a penetrometer tip containing a porę pressure gauge as well. An alternative solution is to establish drained conditions around the cone.

Some preliminary research works have been done (Section 2.6). The intension of this research is presented by professor Janbu, 8. ISSHFE-Conference,

Moscow 1973:    "With the improved inter-

pretation principles, drained static point resistance tests may now seem coh-siderable morę promising for in situ determination of soil parameters, parti-cularly for shear strength parameters on effective stress bases. To clarify the applicability of the principle for vari-ous soil sediments systematic research are encouraged.^M

It is an increasing interest for penetration tests in connection with sea bottom exploration. This is due to the fact that the geological conditions at the Continental shelf, indicates limited applications for sampling equipment (if it is necessary to get undisturbed and comparable samples to considerable depths). The shallow parts of the shelf consists mainly of dense materials. As an example, the depth of penetration at the Ekofiśk area was less than 10 meters, with a maximum available cone resistance of magnitude 40 - 50 MN/m².