Gravitational and tectonic stresses in the rock mass and their determination by measurements in separate pointsJournal: Mining of Mineral Deposits (Vol.11, No. 3)
Publication Date: 2017-09-30
Authors : A. Olovyannyy;
Page : 56-69
Keywords : rocks; stressed state; lateral expansion; tectonic deformations; tectonic stresses; mathematical modeling;
Purpose.Stress state in rock mass is the most important factor affecting processes around mine working. The methods used for calculation of stresses based on hypotheses of elastic thrust, hydrostatic state or spherical equilibrium of the earth crust do not consider tectonic processes and influence of rocks' viscous properties on formation of stress fields. The goal is to develop methods of calculating stress state in rock masses depending on the elastic and viscous rock properties and interaction of tectonic plates considering stresses measured in individual points. Methods. Conditions of stress state formation in rock masses due to gravitation effect are modeled under axial compression of a cylindrical sample with forbidden lateral movements. Solution of the problem about deformation of such sample allowed to obtain the ratio between lateral stresses and axial stresses. This ratio determines the lateral thrust coefficient in the rock mass. Tectonic component of stress state in rock mass is determined by values of deformations in the horizontal plane caused by interaction of tectonic plates. Tectonic components of stresses depend on tectonic deformations in the horizontal plane. Due to the length of tectonic processes the tectonic component of lateral stresses also depends on viscous and elastic deformations. Findings. Gravitation component of the lateral thrust coefficient does not vary with depth, while the tectonic component is inversely proportional to depth. Growth of lateral thrust coefficient as its measurements are approaching the surface is explained by the effect of tectonic component of stresses. Originality.Experimental measurements of stresses are possible only in a limited number of points. There is no other method to determine stresses in masses with non-horizontal bedding, non-uniformities and folds except for mathematical modeling. Within the frames of hypothesis describing a medium with limited linear viscous deformations, we have obtained equations relating the stress components with full and elastic deformations. The method is developed for formulation and solution of problems for modeling stress state using equations of rock mass state as the medium with quasi-elastic properties. Gravitation component is set by the rocks' weight, and effect of tectonics is set by the tensor of tectonic deformations. Practical implications. A method for solving the problem for determination of stresses in rock mass considering measured stresses in individual points is proposed.
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