PSI - Issue 32

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A. Yu. Shumikhina et al. / Procedia Structural Integrity 32 (2021) 224–229 A.Yu. Shumikhina/ Structural Integrity Procedia 00 (2019) 000–000

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Fig. 1. The actual and predicted graphs of the subsidence growth of the surface

Within the considered rheological approach, the analysis of the stress-strain state of the undermined mass was carried out in an elastoplastic setting. An ideal elastoplastic model, which is a generalisation of an elastic and rigid-plastic medium with the internal friction, is used as the constitutive relation for the nonlinear relationship between stresses and strains. The numerical implementation of the mathematical modelling was performed according to the standard finite element method when solving problems in a plane formulation (Zienkiewicz et al. 2013). The finite element procedure to implement the elastoplastic model was carried out in the following sequence: at each time step, condition (2) was checked in all finite elements; in the case of its implementation, the elastic characteristics of the medium of the finite element were corrected: where G is the shear modulus, and к K is the discontinuity criterion of the WS due to shear fractures. Furthermore, the calculation of the stress-strain state of the undermined rock mass was carried out considering the corrected elastic characteristics. The iterative process ended when condition (2) was not met in all the finite elements. Within the elastoplastic model, the localisation regions of plastic deformations in the physical sense were interpreted as the formation of zones of man-induced fracturing of the WS rocks due to the formation of shear fractures. At the same time, according to the seismic exploration results, the spatial position in the undermined mass of the wave anomalies was determined, which were interpreted as zones of decrease in the mechanical properties of the salt rocks due to man-induced disturbances. This correspondence allowed an iterative adjustment of the geomechanical model based on the seismic survey data. During the first stage of the geomechanical calculations, considering the entire set of geological (structural features, the bedding, etc.) and mining (the number of mined seams, parameters of the development system, the mining procedure, the filling of the mined-out space, etc.) factors, we estimated k K G G = (2)