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Expose des conclusions par les Rapporteurs Generaux

Statement of Conclusions by the General Reporters

Samedi 22 Juillet 1761, a 11 h. 30, dans la salle des Assemblees plenieres de PU.N.E.S.C.O.

M. le Professeur A. W. Skempton, F.R.S., assure la presidence de la seance.

Le Prćsident :

The General Reporters will now give their conclusions. I shall cali on each in turn, in numerical order of the sessions. I will therefore ask Prof. Meyerhof if he will be kind enough to present his conclusions from Section I, on Properties of Soils.

SECTION 1

M. G.G. Meyerhof (Canada)

In my opening remarks to Section I, I referred briefly to the three main problems of that section — the classification and description of soils, their physico-chemical and mechan-ical properties, and the methods of their measuremcnt. Within the framework of these problems we had an interesting panel discussion on three specific subjects : the scatter of soil mechanics tests, the porę pressure dissipation and the visco-elastic properties of soils.

On the scatter of soil mechanics tests we heard contrib-utions from the panel members on the variation one could find in problems relating to smali local failures and those relating to large-scale failures, the scatter being greater when one is dealing with a problem of local stability than with one of generał stability. We also discussed theeffects of scatter on the results of soil tests themselves due to vari-ability of samples, variability of tests and also variability of interpretation of the test results, on which there is still a certain amount of further clarification necessary.

On the second subject of the porę pressure dissipation we were discussing the variability one would get by measuring separately the porę air and porę water pressure dissipation, as is of course essential in partly saturated soils. Contributions were madę to indicate that it is necessary to distinguish these two phases of porę pressure dissipation if one wishes to understand fully their behaviour in practice. Discussion took place also on the different tests which have becn developed, in particular the piane strain compression test versus the triaxial compression test. It was shown that the porę pressure dissipation is different, the strain to failure is different, the volume change is different at a given strain and the strength is different, particularly for frictional soils. It was pointed out that this behaviour has important practical applications in the design of foundations, earth retaining structures and earthworks, which are often problems of piane strain rather than of axial symmetrical stability.

Finally we discussed the visco-elastic properties of soils and heard contributions on rheology. Questions arose as to the distribution of the rheological strength between the co-hesion and the friction components and as to what the mag-nitude of these might be. While some of the tests were drained, most of the contributors were still concerned with undrained tests. I should like to emphasise once morę, as I have done in the General Report, that it is essential in long-term stability problems to be concerned with drained tests and that these should also include the rheological properties which we wish to investigate.

The lively discussion and the interesting contributions by the various panel members and other participants have brought out some important results of recent investigations. The wide rangę of this work makes a short summary some-what difficult, especially in such a fundamental field as that dealing with soil properties. The discussion has also indicated some of the gaps in our knowledge, and these may be taken as suggestions for futurę research which might find its way into papers for the next Conference.

In conclusion I should like to thank the members of the panel and other discussers for their contributions, and also express our gratitude to the French Organising Committee for a most interesting and enjoyable Conference.

Mesdames et Messieurs, au revoir, et a Montreal, Canada, en 1965.

Le Prćsident :

I now ask Mr Van der Veen to present his summary in Section 2, on Techniques of Field Measurement and Sampling.

SECTION 2

M. C. Van der Veen (Hollande)

The subject treated in Division 2, techniques of field measurement and sampling, seems to be an important one. Two sub-committees of the International Society, viz. on the penetrometer and sampling, are working in the field of this Division.

To design foundation engineering structures safely and economically it is necessary to take fuli advantage of the soil properties as they are found in each particular case.

This is possible only by investigating the site, making field tests, taking samples for laboratory research and performing measurements during construction and after com-pletion to control what actually is happening. As to this last point, my conclusion, derived from the papers and dis-cussions in Section 2, is that case records are most important, provided fuli details and evidence are given.

I think one of the things everybody agrees upon is that everything should be done to improve sampling technique. The laboratory methods of routine-investigations and research become morę and morę refined. This means that samples have to be undisturbed to such a degree that they do not put a limit to the perfections of laboratory technique.

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