The modulus of deformation of rock mass is an important engineering parameter required for the design of foundation of hydraulic structure and to study the interaction of rock mass and the structure at the foundation support. Different equipment and techniques are used to arrive at the design modulus value. Since any error in the estimation of modulus values results in multiplication of its effects in the analysis, it is necessary to know about the reliability of testing equipment and procedures. In the present study modulus values obtained by different in-situ equipment at different project sites have been compared.


Der Verformungsmodul von der Felsenmasse ist technisch ein wichtiger Parameter, den man zur Konstuktion des Grunds fuer die Hydro - Tektonik, benoetigt um auch die gegenseitige Beeinflussung der Felsenmasse und der Tektonik am Traggrund zu betrachten. Verschiedene Geraete und Methoden werden angewandt, um den Ausfuehrungsmodul -Wert zu erreichen. Es ist erforderlich, die Zuverlaessigkeit der Pruefeinrichtung sowie des Verfahrens zu kennen, da irgend ein Fehler in der Abschaetzung von Modulwerten in der Analyse zu einer Vervielfachung ihrer Einwirkung fuehrt. In der vorligenden Arbeit werden die Modulwerte gewonnen aus unterschiedlichen Einrichtungen an Ort und Stelle and verschiedenen Projekt -Stellen mit einander verglichen.


Le module de deformation d'une roche est un parametre important pour la conception et realisation des ouvrages hydrauliques ainsi que pour etudier l'interaction de la roche et de la structure d'appuis de base. De divers equipments et techniques sont employes pour determiner la valeur de ce module de conception. Puisque l'effet d'une erreur d'evaluation du module devient multiplie dans l'analyse, il est necessaire de savoir la fiabilite des equipments et des methods qu'on ulilise. Dans cette etude, on a compare les valeurs des modules obtenues en employant les equipments in-situ aux sites differents de projets.


Engineering behaviour of the rock mass is described by the discontinuities/joints. The jointed rock mass do not behave elastically. In such cases the determination of deformability, which accounts for both elastic and inelastic behaviour of rock mass and is expressed in terms of Modulus of Deformation (Em). is much more meaningful as compared to Modulus of Elasticity. The deformability is notably sensitive to a scale effect because of the discontinuities. Modulus of Deformation (Em) is defined as ratio of stress (p) to corresponding strain during loading, including elastic and inelastic behaviour (wd), whereas Modulus of Elasticity of a rock mass (Eem) is defined as the ratio of stress (p) to corresponding strain during unloading of a rock mass it include only the elastic behaviour (we), as shown in Figure 1.

There are large variations in the Insitu values of modulus of deformation obtained from different project sites. The modulus of deformation varies considerably due to variable joint deformation properties and variable degree of loosening caused by the excavation process. These variations are also related with quality of rock mass, nature of jointing and other factors such as the local geology and topography of the area etc. Blasting significantly affects the rock mass.

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