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Dynamie probing test (DPA and DPB)

SPT test

Weight sounding test

The recommended standards are given in Appendix A-D. The proposals also include recommendations for presentation of the test results.

3.1 The particular penetrometer selected for the standard cone penetrometer (Appendix A) has been chosen essentially on the basis of its simple geometry. A continuous pen-etration testing procedurę is also recommended .

As other cone penetrometers besides the standard cone penetrometer will continue to be used in the futurę, provision has been madę for them in section 10 of the recommended standard (Appendix A).

3.2 Three different dynamie sounding methods were proposed by the Subcommittee at the Sixth International Conference of Soil Mechanics and Foundation Engineering in Montreal, 1965, (Geotechniąue, Vol 18, No 1, March 1968). However, it has been found desirable to further limit the number of methods. Only one method with two variations has therefore been presented in the recommended standard (Appendix B). The so called light and heavy dynamie sounding methods are not included. As a further step towards standardization, some details of the recommended standard correspond with those in the SPT test.

Light dynamie penetrometers are extensively used in Central Europę. These have been standardized in West Germany (DIN 409** sheet 1 and 2) and in Bułgaria (Bułgaria State Standard 899**“70). These light penetrometers are relatively sensitive and can detect smaller changes of the soil conditions than medium or heavy penetrometers. However, the Subcommittee are of the opinion that in most cases of soft soils the cone penetration test could be used instead of the light dynamie penetrometer to relate the soil conditions.

With heavy dynamie penetrometers it is gen-erally not possible to detect smali changes of the soil density, but these penetrometers can be used to investigate stiff and hard soils at great depths. Because of these ad-vantages the Subcommittee has included some procedures outside the normal rangę of the standard dynamie probing eąuipment.

3*3 The Standard Penetration Test (SPT) is used extensively in North and South America. In Europę this method is commonly used in the UK and in the Southern parts of Europę.

A standard is therefore proposed for the SPT test (Appendix C). It is based on the existing ASTM Standard D 1586-67 (reapproved 197*0, but is morę detailed with respect to the eąuipment and the testing procedurę.

It should also be noted that a hammer with a free fali (as recommended in the SPT test) will give morę reproducible results but smaller N values than a hammer operated by a friction winch with manilla ropę to lift and drop the hammer.

3.** The weight sounding method is exten-sively used in Scandinavia and also in Japan. During the meeting in The Hague in June,

1976, consideration was given to whether the weight sounding method should be standardized. It was recommended that a standard should also be proposed for this method.

The recommended standard for the weight sounding test agrees closely with the existing Scandinvaian standard for this test (Appendix D).

4. RECOMMENDATIONS FOR FUTURĘ RESEARCH CONCERNING PENETRATION TESTING

At the Subcommittee meeting in Ghent,

Belgium, a number of ąuestions were raised about the details of the eąuipment and test procedures which can influence the test results. Also, the interpretation of the test results was discussed. It was decided that the four working groups should propose sub-jects for research with respect to the recommended standards. The Subcommittee hopes that the proposed subjects will initiate research on penetration testing in different countries.

The following subjects were proposed by the four working groups.

The recommended research should be performed on different soils with a rangę of densities and consistencies. Although the research can be performed in the field, some of the factors could be morę easily investigated if the tests can be performed under controlled conditions in a calibration chamber.

4. 1 Recommended subjects for research on the cone penetration test

(a)    The standard penetrometer tip presents the simplest geometry. A systematic study of the influence of the geometry of the penetrometer tip on the penetration resistance is recommended.

(b)    The influence of continuous or discon-tinuous testing on the test results, for a given geometry.

(c)    In the recommended standard, the friction sleeve is located immediately above the cone, and therefore in the special stress field existing at the end of the string of push-rods. There should be a compara-tive study of the results obtained on

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