After emphasizing the need to know the mechanical characteristics of the rock masses found at a concrete dam site, the main types of «in situ» deformability test and «in situ» shear test are referred. The conditions considered most important to be fulfilled by the tests are indicated. Some considerations on the tests used more frequently for obtaining data for the design - viz. punch tests. uniform pressure tests and shear tests are made. Some aspects of the techniques recently adopted by the authors are pointed out. Reference is made to the desirability to get simpler equipment for the tests and an automatic carrying-out of them. Some considerations on the preparation of a plan of tests, its principal aspects and the elements which must accompany it are indicated. Finally a reference is made to the planned studies of the Gran Suarna Dam site, which are considered sufficiently typical for presentation to the Congress.
Après souligner la necessite de connaître les caracteristiques mecaniques des massifs rocheux de fondation d'un barrage en beton, necessaires pour leur projet, on rapporte les principaux types d'essais «in situ» de deformabilite et de cisaillement pour obtenir celles-là. On indique les conditions considerees les plus importantes à remplir par ces essais. Quelques considerations sont faites sur les essais qui semblent les plus convenables pour le projet, c'est-à-dire essais de poinçonnement, de pression uniforme et de cisaillement, soulignant certains aspects des techniques recemment employees par les auteurs. On fait reference à la convenance d'obtenir un equipement plus simple pour les essais et pour son execution automatique. On fait quelques considerations sur l'elaboration d'un plan d'essais, ses aspects principaux et les elements qui doivent l'accompagner. Finalement ont fait reference au plan d'essais pour la fondation du barrage de Gran Suarna que l'on considère suffisament typique pour être presente au Congres.
Nachdem die Notwendigkeit, die fuer das Projeckt eines Staudammes aus Beton notwendigen mechanischen Eigenschaften der Felsmassive n des Baugrunds zu kennen, hervorgehoben wird, werden die verschiedenen Versuchstypen an Ort und Stelle ueber die Verformung und Rissigkeit erwahnt, um diese Werte zu erhalten. Es werden die wichtigsten erörterten Bedingungen, die in diesen Versuchen erfuellt werden muessen, hervorgehoben. Es werden einige Erörterungen ueber Versuche gemacht, die fuer das Projekt am geeignetesten erscheinen, so zum Beispiel Stichproben, Versuche ueber gleichmassigen Druck und ueber Risse, indem manche Aspekte der von den Autoren kurz- lich benutzten Methoden besonders hervorgehoben werden. Es wird ueber den Vorteil berichtet, eine einfachere und automatisch ablaufende Versuchseinrichtung zu erhalten. Es werden einige Erörterungen ueber die Aufstellung eines Versuchsplans, seiner besonderen Aspekte und die miteinzubeziehende Punkte gemacht. Zuletzt wird ueber den Plan fuer den Ort des Staudammes des Gran Suarna berichtet, der ats genuegend typisch angesehen wird, um dem Kongress vorgestellt zu werden.
Some facts have contributed so that this aspect becomes more important each time. Among them:
the need of constructing higher and more complex dams using in a better way the qualities of the concrete and transmitting greater loads to the foundation.
the accidents which occurred with dams and tunnels as a result of poor rock behaviour,
the necessity of constructing dams in places that show deficient foundations characteristics and
the belief that a great lack exists in the knowledge of the behaviour of rock masses, since the importance on that behaviour of their heterogeneous, anisotropic and discontinuous nature became evident.
«In situ» tests furnish valuable information for the design and permit the gathering of data about the rock mass behaviour and about their mechanical characteristics. The comparison of this information with the one obtained by means of the theories established on different basic hypotheses can be of major importance for the advancement of the knowledge of rock mechanics. Equally important will be the comparison of the data of observing the behaviour of the dam foundations with the corresponding data derived from calculations and model tests in which geotechnical details are considered. Besides the development of theories and model test techniques adequate to the study of a rock mass behaviour, the development of new «in situ» test techniques of the rock masses are equally important [1]. Those tests that represent in a better way the action of the dam against the foundation and the new observation techniques of the foundation behaviour [2 and 3] look today of relevant interest. The present paper discusses methods in use for the «in situ» determination of the mechanical properties of rock masses, making a reference to the techniques adopted in the tests under way at Gran Suarna Dam site.
The basic elements necessary for a dam design are obtained today from «in situ» tests, i. e. from the adequate interpretation of the results of deformability and shear tests.