The results of the research on the phenomenon of sudden jump of compressive deformation during the experiments of compressive unstable failure of rock are presented in this paper. The full process of unstable rock failure with sudden deformation jump has been recorded by means of the self-designed photo-electric displacement sensor. The analytical expression of the sudden jump of deformation is obtained based on the theoretical analysis of the loading system.
La recherche menee sur Ie phenomène de saut soudain de la deformation comprimee durant l'experience instable du concassage de roche est presentee dans ce texte. Tout Ie processus du concassage instable de roche, y compris Ie saut soudain de la deformation, a ete enregistre par Ie senseur au deplacement photoelectrique concu de soi-même. Pour I'analyse theorique du système de charge s'est offerte I'expression analystique de saut soudain de la deformation.
In diesem Text sind die Forschungsergebnisse ueber die plötzlichen Veranderungsphanomen der Druckdeformation, die wahrend des Experiments von Felsbruch und Stabilitatsverlieren entstand, vorgestellt. Mit Hilfe von den von uns selbst konstruierten photoelektrischen Sensoren haben wir den Voll-prozeβ von Felsbruch und Stabilitatsverlieren aufgezeichnet. Durch die theoretische Analyse ueber die Belastungssystem ist die analystische Losungen von dieser plötzlichen Veranderung erzielt.
The phenomenon of the sudden deformation jump during unstable rock failure has been one of the key issues of the research on the instability of rock deformation. Due to the limitations of the testing systems used before the 60s, the sudden deformation jump during the loading tests of rock failure could not be adequately recorded, and it was impossible to carry out the research on the full process of unstable rock failure. After the 60s, by increasing the stiffness of the test machine and especially by introducing the servo-controlling mechanism to avoid the Instability of loading process, it is possible to experiment the full process of rock failure under the stable loading conditions. The phenomenon of sudden deformation jump related to the instability during loading, however, no longer occurs in the experiments. Apparently, it is very difficult to study the instability problems of mechanics occurred in rockbursts and seismic activities, etc., by using the traditional stiff loading or servo-control in the research on the failure process of rock. The experimental research on the deformation sudden jump during the precursory deformation and main failure in the process of unstable rock failure was conducted under the unstable loading conditions. The full process of the unstable rock failure with the sudden deformation jump was measured by means of the self designed photo-electric deformation sensor. Then the analytical expressions of the precursory deformation and the sudden deformation jump were obtained based on the theoretical analysis of the loading system, and the influence of stiffness of testing machine on the sudden deformation jump was discussed in detail.
In the loading experiments of rock failure by using the so-called conventional testing machine the duration of deformation unstable process is very short and the magnitude of the deformation rate is very high. In practice, therefore, there exist two processes with different deformation characteristics, i.e, the quasi-static process before the load reaches its strength limit and the dynamic process of the unstable failure. It is impossible for the convention testing system to response to the drastic change of deformation rate around the unstable point. It is very difficult to record the full process by using the conventional transducers with relatively low working frequencies and recording devices with low frequency response. This is the reason why it is impossible to record the full stress-strain curve by using the conventional testing machines.. Therefore, if the conventional testing machines were to be used in the research on the unstable rock failure, it is imperative to increase the frequency range of the transducers and enhance the frequency response characteristics of the recording devices to cope With the dynamic process of unstable rock failure. Despite the short process of unstable rock failure the duration of the unstable stage is by no means equals zero under the conventional non-controlled loading conditions. By enhancing the frequency response characteristics of the recording system, the full process can be recorded, though C.A. Tang(l993).
