Abstract
Methodological approaches to the selection of ultimate state criteria and strength characteristics of the repeatedly undermined rock massifs were developed. These approaches were designed to provide parametric support to the geomechanical modelling of the massif stress-strain state and the mining systems of the Starobin potash deposit mine fields planned for the additional mining of the mineral reserves left. It was established that a complex criterion must be used to study the massif ultimate state. Determination of such criterion can be carried out using the developed approaches. The first approach is to select several criteria that evaluate the massif ultimate state by certain types of the massif stress-strain state. These criteria are the following: the criterion of the maximum normal stresses, criterion of the maximum linear strains, the criterion of the maximum shear stresses and the Coulomb–Mohr failure criterion. The second approach is to construct an integrated failure state criterion for materials whose ultimate tensile and compressive stresses differ significantly. In this case, parameters characterizing the type of stress state and properties of the material are introduced. These parameters together determine the destruction character – tear or shear. To describe the rocks behavior in the extreme strength stage of deformation, it is proposed to apply deformation theory of strength using the developed strain failure criterion. When calculating the strength characteristics of the repeatedly undermined rock massif, it is recommended to use a structural attenuation coefficient as the product of several factors, taking into account various types of disturbances in the primary undermined massif and the time factor. The Coulomb–Mohr strength condition is recommended to be used taking into account the composite structural attenuation coefficient. Dependencies have been developed to describe the change in the strength characteristics of rocks in the undermined massif, considering the attenuation coefficient.
Highlights
At the present time, additional mining of the previously mined out panels is actual for the Starobin potash salt deposit in order to extract the left ore reserves concentrated in the protective and inter-chamber pillars and the underworked sylvinite layer
The purpose of this study is to develop methodological approaches to the selection of ultimate state criteria and strength characteristics of the rock massifs being undermined repeatedly, as applied to the Starobin deposit conditions
Methodological approaches to the selection of ultimate state criteria and strength characteristics of the repeatedly undermined rock massifs were developed
Summary
Additional mining of the previously mined out panels is actual for the Starobin potash salt deposit in order to extract the left ore reserves concentrated in the protective and inter-chamber pillars and the underworked sylvinite layer. The acceptance of a certain criterion as an estimate of the ultimate (critical) rocks state must be reasonable and based on the regularities and features of the physical process being considered. No such studies were carried out at the Starobin deposit. The problem of selecting the ultimate state criteria and strength characteristics of the rock massifs being undermined repeatedly was not solved as applied to the conditions of the Starobin deposit. Reliable experimental data for the considered class of problems (stability of underground structures in repeatedly mined rock massifs) is still insufficient
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