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time; and if they were not satisficd with this knowledge they took very active steps either to improve upon it or to make adequate allowances for its shortcomings. Optimism and over-confidence may impress one's clients, but they have no influence on the great forces of naturę.

Futurę prospects

These are sonie of the darker aspects of the futurę, but what are the brighter prospects ?

In design and construction we can be surę that tremendous advances will be madę. It is, after all, only in coniparatively recent years that the fuli impact of soil mechanics has been felt in civil engineering practicc. Yet already we are in a new epoch. Great buildings are being erected in cities where, a generation ago, no one dared build to morę than five or six storeys. In parts of the world where increased water supplies are dcsperately needed for the maintenance of life itself, earth dams are being constructed to heights of 100 or 150 metres, at sites which would absolutely preclude a con-crete dam of any type. And where good foundations exist rock-fill dams with clay cores are now under construction to heights of about 200 metres or even 280 metres in the case of Nurek dam. Also the techniąues at the contractor’s disposal for mastering diflicult underground conditions have altered almost beyond recognition.

In research, there is a very great deal of work still to be done in the laboratory, in the field and the derivation of new theoretical concepts. The younger members here need not feel that most of the discoveries have been madę, and that little remains for them but tidying up and filling in details. We are dealing with the highly complex behaviour of parti-culate matter, and although a working knowledge of this class of materials has now been attained; from a morę basie point of view we have barely started to understand the pro-blems involved. There is no doubt about this. We are working with materials which, in any rigorous sense, do not obey the laws of elasticity or even those of classical plastic theory. And a most distinguished engineering scientist said to me not long ago that it seemed to him almost miraculous that we had been able to get as far as we have with such unpro-mising stuff as soils.

Unpromising they may be. But the problems are there and provide an inspiring challenge to the research mind. More-over the methods of analysis devcloped in soil mechanics, and especially the principle of effective stress, are now beginning to open a whole new field of enquiry and we see rock mechanics becoming established as a sister science. Indeed, to my mind, there is no philosophical distinction between rocks and soils. The geological materials, from sands and clays, through soft sandstones and shales to the harder sedimentary and igneous rocks, form a continuous series; and the laws governing their behaviour must be the same, fundamentally.

It is therefore evident that we must study rock mechanics as well as soil mechanics. With rocks, field tests are of even greater importance, as the in-sifu structural features are morę significant. But the methods of test are similar and, in the laboratory, there is no essential difierence. The civil engineering applications of rock mechanics are growing in number and importance, and sonie of the most troublesome problems within the entire rangę of geotechnical studies are those involving the soft rocks, such as clay shales, which lie pre-cisely at the borderline between the two main groups of materials.

Hence we should explicitly recognise rock mechanics as being within the scope of this Society. I am aware that a few papers on this subject have been presented to our Confe-rences, but we may expect and hope to have morę. Perhaps in 1965 we might allocate a separate Session to the properties of rocks; but the matter is of some urgency and I suggest that those actively interested in rock mechanics should be invited to attend a smali Regional Conference in about two years time, similar to others of a similar naturę which havc been held in the past with extremely valuable results. We are, in fact, concerned with engineering problems in all types of geological materials. This should be recognised in the uni-versities, in the engineering profession, and not least by ourselves.

Apart from mentioning this point I shall not attempt to make a list of other matters which still await research and clarification. Many of these will be discussed during the tech-nical Sessions in the next few days. And one does not need to spend very long in a research laboratory or on an engineering job to realise there is ample scope for further investigations.

Meanwhile there are many old friends to meet and new friends to make. Our previous Conferences have been most fruitful in the exchange of ideas and in the possibilities they have given for establishing personal contacts with people from other countries. It is a safe assumption that the present occasion will prove to be equally successful, and it is therefore with the greatest pleasure that I open the 5th International Conference of our Society.

M. A. Mayer, Yice-President pour PEurope de la Societe Internationale, clótura la seance en ces termes :

Messieurs les Presidents, Mesdames, Messieurs,

Lorsque notre Comite nPa demande de prendre la parole devant vous je me suis souvenu de la phrase que La Bruyere a placee en tete de ses « Caracteres » : « Tout est dit et Pon vient trop tard depuis plus de sept mille ans qu’il est des hommes et qui pensent ». Succedant a cette tribune aux eminentes personnalites que vous venez d’entendre, j’ai pense moi aussi que tout aurait ete dit et que mon interven-tion serait bien inutile.

Mais je viens d’entendre les discours qui ont ete prononces et tout particulierement celui du Prof. Skempton. Notre cher President et Ami vous a rappele rapidement quel avait ete le role de notre pays dans le developpement des etudes qui nous reunissent; il a signale en particulier la misę au point des injections dans les terrains d^łalluvions et il a cite a cette occasion le nom de M. Ischy et le mień. J’en ai ete tres honore; mais je crois de mon devoir de rappeler que des 1925 Joosten avait en Allemagne mis au point le procede qui porte son nom et que peu apres, a Poccasion des travaux de Bou Hanifia, le Professeur et Mme Terzaghi, que nous regrettons tant de ne pas voir ici, avaient realise eux aussi Petanchement par injections de couches de sables fins. D'autre part, si le Prof. Skempton n’a cite que nos deux noms je tiens a dire qu’il s’est agi en Pespece d’un travail d’equipe; je suis heureux de saisir Poccasion de remercier tous ceux, et il y en a plusieurs dans cette salle, qui y ont participe, il y a maintenant pres de 25 ans.

Mais si le Prof. Skempton a rappele quel avait ete le role de la France dans le developpement de la Mecanique du Sol, je voudrais a mon tour indiquer quel a ete celui de la Grande-Bretagne et notamment celui du Prof. Skempton lui-meme et de Pequipe dont fait partie le Dr Bishop, qu’il a reunie autour de lui. C'est a eux que sont dues les etudes et les deve-loppemcnts experimentaux sur Pinfluence de la pression interstitielle dans les sols, etudes qui sont maintenant devenues classiques. A ce titre ils ont droit a toute notre gratitude.

Notre President M. Caquot a remercie en notre nom tous les organismes publics et prives qui nous ont donnę les moyens

42

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