Gradient Method Applied to the Time-Dependent Behavior of Rocks

Experimental research, both in situ and in the laboratory, allows obtaining the cumulative effect of all determining factors, without the possibility of separating the effects of each one. Due to this fact, as well as because mining develops in different geomechanical conditions, specific to each deposit or even part of the deposit, the problem of ensuring the stability by evaluating the pressure manifestation regime has a local aspect. The results of these researches can be used in order to: improve the existing support monographs, by choosing the optimal support density; establish a correct support technology; establish the appropriate difference between the digging front and support front, etc.; design new types of support; assessment of the effectiveness of the new sup-port technologies in the given geomechanical conditions; optimization of supporting monographs that must be analyzed from the point of view of maximum satisfaction of the required conditions on the work by its role in the production process, throughout its existence, with minimal execution, maintenance and exploitation expenses and in perfect conditions of work safety. For this purpose, the measurement methods and equipment must focus on determining: the movement of the surrounding rocks; the deformations of the underground work profile; the displacements and deformations of the support system; and the loads on the support. Most problems related to mining pressure and mining stability in the underground activity domain must be solved by considering the time behavior of rocks through an approach of the interaction amidst the rock massif, support system, time through the elastic, viscous, and plastic models, namely a rheological approach. To select a rational support system, one must be aware of the sustainment solicitation at various time intervals. Only in analytical research, where the massif is studied and characterized in terms of rheological behavior, is the change in sustainment in time highlighted. The gradient method used in this case is based on the evolution of the final deformations at a given time in comparison to their previous evolution. The paper is divided into two sections: experimental and interpretation of experimental data, which demonstrate the author's methodology for assessing the rheological behavior of analyzed andesite as a result of theoretical and experimental research on the analyzed rock types. Based on the deformation and the time curve of the horizontal mining work contour, the mathematical function was established, which expresses the law of sought deformation. At the same time, the rheological model capable of describing the behavior under a load and under extremely adverse conditions is proposed.