No abstract

A method for optimizing the protecting pillars parameters during the study of soft enclosing rocks (in Ukraine mines) is represented. The necessity of a differentiated approach has been substantiated when choosing the protecting pillar parameters based on the geomechanical factors analysis influencing the state of massif. Mining and geological situation was analysed. It has been studied a stress-strain state (SSS) along the protecting pillar width with account of the mined-out space on the basis of a computational experiment and is presented in the form of curves of vertical and horizontal stresses distribution, as well as stresses intensity distribution. The recommended engineering decisions have been substantiated and the SSS of fastening and security structures has been analysed. A certain reserve of the fastening structure loadbearing capacity as part of the frame support and the combined roof-bolting system has been revealed. An evidence base has been created for the measures development on conducting and maintaining mine workings in the zone of the stope works influence. The recommendations have been developed on the protecting pillar formation with a width of at least 40 -45 m to exclude the stope works influence.

Purpose. Substantiating the method for forecasting rock pressure manifestation in the system "layered massifworking support" on the basis of displacement patterns detection at any arbitrary point of the preparatory working circuit during the computational experiments. Methods.Computational experiments were carried out on the basis of the finite element method using the solid computational domain, provided superlimiting non-linear behavior of the simulated materials. The use of numerical grid methods allows creating geometrically and physically complex simulation models and manipulate their state within a wide range.Findings. The calculations defined that with weak links between adjacent strata, acting shear stresses destroy them in the vicinity of working, and the contiguous rock strata deform with mutual sliding. Analysis of reduced stress area allows to substantiate with accuracy sufficient for mining computations a unified average structure of the computational domain that most comprehensively reflects all the main features of a real mining massif which are likely to influence computational error. This choice ensures the introduced error value within 10% in the entire range of mechanical parameters change of the rock massif strata.Originality. Stress-strain state of frame support and patterns of its change with increasing mining depth are nonlinear, especially with nearby rock strata entering the superlimiting state; formation of the plastic hinges system along the frame support circuit, which causes the development of such replacements that exclude the possibility of further working exploitation.Practical implications. The proposed method allows to determine the optimal indicators of maintaining a working driven in the finely-layered rock massif, which makes it possible to significantly reduce operation costs.

The purpose of this study is to determine the nature of influence of the rheological properties of the rocks on the results of computational experiments simulating the mine workings contour condition during the breakage face advance. To determine the deformations along the mine workings contour, the calculations have been made of the junction area between the preparatory and stope face mine workings by the finite element method for various parameters of the material models. These data provided the basis for analysis of the patterns development of the rheology modelling influence on the stress-strain state of the geomechanical system. The obtained patterns are described by a function of many variables, and this function determines the limit and degree of rheology effect on the results of calculations. For the first time this pattern takes into account the heterogeneity of the rheological characteristics of rocks and the specifics of the computational domain geometry. The use of the obtained patterns makes it possible to simplify significantly the process of modelling in time and space of the geomechanical systems, which have a complex structure describing the interaction of several objects.