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local side friction f_s to the cone resistance q_c, has to be expressed as a percentage in order to obtain a figurę larger than one. Although in the past the friction ratio has been mostly used, there is a tendency to use the friction index If, being the ratio of the cone resistance q_c to the local side friction f_s, and which gives directly a figurę larger than one. This is the reason why the two quantities have been included in the definitions.

Notę 3: The friction sleeve 3-5

The roughness is defined as the mean devi-ation of the real surface of a body from the mean piane. The roughness is expressed in micrometers (pm).

Notę Discontinuous testing 10.^.2

In the case of mechanical penetrometer tips, in order to be certain that the cone and the friction sleeve move sufficiently with re-spect to the push-rods, due account is to be taken of the elastic shortening of the inner rods. Therefore, at the surface the movement of the inner rods relative to the push-rods must be at least equal to the sum of the minimum imposed movement of the cone plus the elastic shortening of the inner rods.

Notę 5: Mechanical penetrometer tips 10.5-1

Continuous testing with a mechanical penetrometer tip is not recommended for high accuracy, as the movement of the inner rods to the push-rods can change its sense at different depths, increasing the margin of the error due to the parasitical internal friction. Purthermore it is necessary to check at least every meter during the test that the inner rods are still free to move relative to the push-rods.

Notę 6: 10.5-1 M*J

In the case of the simple cone special pre-cautions have to be taken against soil entering the sliding mechanism and affecting the resistance. After extracting the penetrometer tip a check is to be madę, in order to be certain that the cone-stem still moves completely freely relative to the bush.

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