No abstract

Purpose. Substantiation of the mechanism of loading the preparatory mine working support to optimize its deformation-strength characteristics based on the calculation of the stress-strain state of the "massif -support" system. Improving the cost effective technologies for fastening and maintaining the preparatory mine workings.Methods. The analysis of the elements interaction modes of the "massif -support" system has been performed by the two-parameter diagram for optimizing the deformation-strength characteristics of the rock massif and the preparatory mine workings support using the research results of the stress-strain state of a system by means of finite element method. A comparison has been made of computational experiment with mine instrumental observations.Findings. The geomechanical model of the computational experiment on the choice of operation modes of the fastening system, as well as the methodology of the approach to optimize the process of interaction between the massif and the support have been substantiated. The analysis of search patterns for the rational deformation-strength characteristics of the fastening system in the preparatory mine working, taking into account the influence of the main geomechanics factors on this process, has been developed and performed.Originality. The patterns have been established of the geomechanics factors influence on the choice of rational operation modes of the load-bearing elements of the fastening system and the support in general based on research of the stress-strain state of the "massif -support" system. The optimization principles of interaction based on the analysis of a two-parameter interaction diagram have been substantiated.Practical implications. The wide perspective has been substantiated for strengthening the soft rocks in reusable preparatory mine workings with combined roof-bolting systems, which makes possible to realise the resource-saving conditions of maintenance. The calculations have been made with account of the optimization criteria for interaction of massif and support.

Purpose. The purpose is to develop the calculation methods for minimizing the load on the fastening system of the preparatory mine working in difficult mining and geological conditions of its maintenance. Methods. By analysing the multivariate computational experiments on the study of the stress-strain state of the load-bearing elements of the ‘massif – support’ system in the preparatory mine workings by means of the finite-element method, as well as mine observations and measurements of displacement in the coal-overlaying rock formation. Findings. An algorithm has been developed for searching the rational modes of the fastening system resistance and methods for minimizing the load on the support of the preparatory mine working, maintained in very complex mining and geological conditions. Originality.The methodical principles have been developed of minimizing the load on the fastening system of the preparatory mine working, which are based on the use of a combination of stress-strain state studies of the ‘massif – support’ system by means of the finite element method and provisions of normative documents for calculating the dimensions of the dome of natural equilibrium of the mine working roof rocks. Practical implications. The operation modes optimisation of the load-bearing elements interaction of the mine working fastening system reduces the material and labour costs during its construction and increases its stability during operation. Keywords: analysis, calculation, optimization, support, preparatory mine working, stope works, roof rocks, collapse

The objective of this work is to study the relationship of the deformation-strength characteristics of the fastening system with its displacement value. The tendencies of influence are divided into two groups. The multivariate computational experiments have been performed in the conditions of coal-face works. It is shown the influence of geomechanical conditions of the mine working maintenance on the fastening system operating mode change when choosing its rational deformation-strength characteristics. On the basis of the performed studies, it was concluded that it is necessary to adjust the fastening elements of each specific support setting scheme. This is necessary to provide recommendations for the maintenance schemes optimization of reusable extraction workings.

The degree of influence has been determined of diversified deformation-strength characteristics of load-bearing elements in the fastening system of the preparatory mine workings, while maintaining them in a laminal massif of soft rocks. The analysis has been performed of multivariate computational experiments of the stress-strain state of the load-bearing elements of the fastening system in the preparatory mine workings from the position of the mutual influence of their deformation-strength characteristics and the support loading as a whole. An analysis is represented of the mutual influence of the operation modes of the mine working support elements between themselves and the fastening system as a whole; it has been studied the stress-strain state of the mine working fastening system with a central hydraulic prop stay, as well as a significant increase in reliability of the support performance has been analysed and determined. The tendency has been substantiated of minimizing the load on the mine working fastening system – increasing the coherence of the diversified operation modes of fastening elements by enhancing preferentially the yielding property of the rigid element. The application has been substantiated of the central yielding prop stays of the strengthening support of a frame in case of intensive rock pressure manifestation in the zone of the stope works active influence.

The new support patterns have been revealed for controlling the combinations of the roof rocks strengthening processes in extraction mine workings with combined roof-bolting systems. It has been established that in adjacent roof rocks, by means of a combination of rope bolts and resin-grouted roof bolts, an armored and rock plate is formed, the high load-bearing capacity of which is achieved by maintaining the horizontal thrust forces that reduces the concentrations of all the stresses components to a level many times lower than the strength characteristics of the lithotypes. The criterion has been substantiated for assessing the resistance level of roof-bolts as a part of the combined roof-bolting system, which is used for determination of the most important geomechanical factors in terms of the system loading degree. The patterns have been established of a degree of loading the roof-bolts being a part of the combined roof-bolting system from the main influencing geomechanical factors. The calculated expressions have been obtained to determine the needed parameters for effectively strengthening the roof in workings by a combined roof-bolting system. The mine experiment analysis has been performed as well.

Purpose. Substantiate the expediency of optimizing decision-making in resource-saving maintenance of mine workings. Methods. The concept of ensuring the conditions for the repeated use of mine working is based on modern methods of managing the rock pressure manifestations, conducting multifactorial computational experiments, experimental verification of the principles’ implementation during effective use of resources in full-scale conditions. Findings. The directions of improving the fastening and protection structures, which ensure the stability of reused mine workings, have been determined. In this case, the most lightweight protection structure is proposed, the functions of which are transferred to the collapsed and compacted rocks of the uncontrolled collapse zone. Originality. The basic concept of repeated use of mine workings, taking into account resource-saving technologies, has been formulated and implemented. The stress-strain state of the “mass – support – protection elements” system has been studied, and its rational parameters have been optimized. An example of an optimization solution based on the stated methodology is presented. Practical implications. The schemes have been developed for calculating the parameters of loading the fastening and protection structures in reused mine workings with a geomechanical substantiation of the adopted provisions and assumptions, which is the basis for issuing recommendations to ensure the mine working stability.

Substantiation of calculating the rational parameters of reaction and yielding property of the fastening system in the preparatory mine workings. Methods. The stress-strain state analysis of the "massif -support" system and the normative documents on support calculation of the preparatory mine workings to determine the patterns of link between the fastening system parameters and the main geomechanical factors. Findings. The patterns of geomechanical factors influence on the parameters of reaction and yielding property of the fastening system have been determined, as well as the analytical expressions for their calculation have been obtained. Originality. Correlation-dispersion analysis of the optimization data has revealed a stable exponential relation between the parameters of reaction and the yielding property of support with an index H/R, regardless of the coal-bearing massif structure. Practical implications. Calculation of the deformation-strength characteristic of the fastening system has been developed depending on the mining and geological conditions of maintaining the preparatory mine working.