A retrospective analysis of some geomechanical classifications for rock masses is presented. It is shown that estimates of rock mass strength according to geomechanical classifications developed, e.g., for construction of tunnels and for ore mines can differ very much. Development of specifically oriented classifications for rock masses with certain geomechanical properties is required.
Es wurde eine retrospektive Analyse einiger geomechanoschen Klassifikationen von Gesteinsmassiven durchgefuhrt. Es idt aufgezeigt worden, dass die Bes-timmung der Festigkeit des Massivs nach geomechanischen Klassifikationen, die z.B. fur den Bau von Tunnelen und fur Erzbergwerke entwickelt wurden, sich um etliche Male unterscheiden kann. Es ist eine Entwicklung von spezialisierten Klassifikationen fur Gesteinsmassive mit bestimmten geomechanischen Eigenschaften erforderlich.
Il a ete fait l'analyse retrospective de certaines classifications geomecaniques des massifs de roche. Il a ete montre que les estimations de solidite du massif suivant les classifications geomecaniques etudiees, par exemple, pour la construction des tunnels et pour les puits de minerai peuvent differer en quelques fois. Il est donc necessaire d'etudier les classifications specialisees pour les massifs aux proprietes geomecaniques particulieres.
Rock masses are such media whose properties has been generated by the Nature and cannot be estimated before the construction of underground structures without deep penetration into a rock mass in contrary to man-made materials (metals, concrete, polymers and so on). Such a specific situation in the field of mining frequently results in the uncertainty of strength, deformational and other characteristics that are set for calculations of stability of rock mass structures or parameters of supporting structures. It is the cause of quite often failures during construction and operation of underground mines and other objects, in some cases with fatal consequences for personal and with great economical losses.
Obtaining data on the properties of the rock masses in the whole spectrum of geological state and geomechanical state is a problem that is hard to be resolved. It is aggravated by the fact that these properties additionally depend on the dimensions of the rock mass area that is of interest. On the other hand, the study of properties both of a rock mass and any other deformed medium is possible only by means of in-situ experiments.
The complexity of the problem of studying the mechanical properties of a rock mass is in the fact that in-situ experiments with testing the rock mass volumes with linear dimension of the first ten meters require application of powerful and cumbersome press units, special planning and organizing of mining operations and significant financial support. Therefore very little amount of results of such studies is available so far. Furthermore such tests in the rock masses measuring some tens of meters or over are difficult to accomplish from the technical point of view. Properties of such rock volumes are determined in very seldom cases and these data are difficult for application in other situations without establishment of some regularities that make possible such an application of available data.
