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bility many times larger than that of the sensing devices. The crosssectional area A_e of the gap, remaining after deduction of the area occupied by the seal must be smaller than 0.10 cm² (see cross-hatched area in Fig. lc). The outer limits of the gap are to be shaped in such a way that the measurements are not affected by the possible entry of soil particles.

3.4 Sensing devices.

The sensing device should be designed to measure the cone resistance without being influenced by a possible eccentricity of that resistance.

b c ♦ od < U %o FOR THE 5 LOWER PUSH RODS ^Qb <8 %o FOR THE OTHER PUSHRODS

3.5 Friction sleeve (Fig. Ib).

The diameter of the friction sleeve is to be manufactured and the sleeve retained in operation, only so long as it is at least the same value as the base of the cone, with a tolerance of +0.35 mm.

The surface area of the friction sleeve shall be 150 cm² with a tolerance of +2%.

The surface of the friction sleeve shall have a manufactured surface roughness of 0.5 ym (see notę 3 para. 11) with a tolerance of +50* in the direction of its longi-tudinal axis. In operation this roughness shall not become smaller than 0.25 ym. The projection above and below the friction sleeve shall correspond with the other parts of the penetrometer tip.

The friction sleeve is to be located immedi-ately above the cone (Fig. Ib). The annular spaces between the friction sleeve and the other part of the penetrometer tip and their seals must conform to the same specifi-cations as described under 3.3.

3.6 Push rods.

The push rods are screwed or attached together to bear against each other and to form a rigid-jointed series with a continu-ous straight axis. The deviation from the axis should not exceed 4£*) for the five lower push rods of the series and ^x) for the remainder. The manner in which the ^ł,deviation" is determined is shown in Fig.

3.

When measuring the total friction with push-rods their diameter over the total length shall be 36 mm with a tolerance of +1 mm.

^x These deviations corresponds m case of an even curvature to a deflexion of 1-2 mm in length.

Fig 3. Determination of the deviation from the straight axi$ for push-rods.

3-7 Measuring eąuipment.

The resistances are to be measured by de-vices attached to the cone and the friction sleeve if included, and the signals are to be transmitted by a suitable method to a data recording system.

Exclusive recording of test results on a tape, which does not permit direct accessi-bility to the data, is not recommended.

3.8 Thrust machinę.

The machinę shall be able to provide a stroke preferably of one meter, and shall push the rods into the soil at a constant ratę of penetration. The thrust machinę shall be anchored and/or ballasted such that it does not move relative to the soil surface during the pushing action.

3-9 Friction reducer.

If a friction reducer is included, it should be located at least 1000 mm above the base of the cone.

4. STANDARD TESTING PROCEDURĘ 4.1 Continuous testing.

The standard testing procedurę is that of continuous penetration testing, in which the measurements are madę while all elements of the penetrometer have the same ratę of penetration .

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