scholarly journals Regularities in formation of stressed state in roof rocks of mined-out space during development stage

2022 ◽  
pp. 68-75
Author(s):  
V.N. Zakharov ◽  
V.A. Trofimov ◽  
A.V. Shlyapin
Keyword(s):  
Coal Seam ◽  
Development Stage ◽  
Stress And Strain ◽  
Formation Water ◽  
Variable Theory ◽  
Complex Variable Theory ◽  
Compressive Stresses ◽  
Roof Caving ◽  
Deformation Processes ◽  
Roof Rocks

Formation of the stress-and-strain state of the rock mass in the roof of mined coal seam depends on the development of the mined-out space. It is believed that the coal seam is located deep enough and it can be assumed that the effect of the daylight surface on its condition can be neglected. In this case, the solution is based on the analytical approach using methods of the complex variable theory and it is reduced to the construction of a single permission analytical function. The paper reviews the evolution of the deformation processes in development of the mined-out space in presence of a hard-to-collapse elastic roof, which is capable of sinking smoothly over time, without sudden caving on the landings on the floor. A particular attention is paid to the phase when the roof and the floor touch each other, i.e. the roof caving, starting from the first touching and up to its complete caving. In this case, two sections of the hanging roof are formed, that are gradually reducing in length as the dimensions of the mined-out space increase. The area of roof caving is progressively increasing, and the vertical compressive stresses at the boundary are gradually rising, tending to reach the initial vertical pressure at the depth of the formation before the start of its mining. Tension zones relative to the horizontal and vertical stresses are identified, that are attributed to the areas of roof hang-up, which may determine the location of zones with higher methane and formation water permeability, both in the rocks between the seams and in the coal seam.

scholarly journals Geophysical Evaluation of Effectiveness of Blasting for Roof Caving During Longwall Mining of Coal Seam

2019 ◽  
Vol 177 (2) ◽  
pp. 905-917 ◽  
Author(s):  
Łukasz Wojtecki ◽  
Petr Konicek ◽  
Maciej J. Mendecki ◽  
Iwona Gołda ◽  
Wacław M. Zuberek
Keyword(s):  
Coal Seam ◽  
Stress Drop ◽  
Longwall Mining ◽  
High Energy ◽  
Longwall Face ◽  
Seismic Moment Tensor ◽  
Coal Seams ◽  
Rockburst Hazard ◽  
Roof Caving ◽  
Roof Rocks

Abstract Deep longwall mining of coal seams is made in the Upper Silesian Coal Basin (USCB) under complicated and mostly unfavourable geological and mining conditions. Usually, it is correlated with rockburst hazard mostly at a high level. One of the geological factors affecting the state of rockburst hazard is the presence of competent rocks in the roof of extracted coal seams, so rock falling behind the longwall face does not occur, and hanging-up of roof rocks remains. The long-lasting absence of caving may lead to an occurrence of high-energy tremor in the vicinity of the longwall face. Roof caving behind the longwall face may be forced by blasting. The column of explosives is then located in blastholes drilled in layers of roof rocks, e.g. sandstones behind the longwall face. In this article, a characterization of tremors initiated by blasts for roof caving during underground extraction of coal seam no. 507 in one of the collieries in the USCB has been made using three independent methods. By the basic seismic effect method, the effectiveness of blasting is evaluated according to the seismic energy of incited tremors and mass of explosives used. According to this method, selected blasts gave extremely good or excellent effect. An inversion of the seismic moment tensor enables determining the processes happening in the source of tremors. In the foci of provoked tremors the slip mechanism dominated or was clearly distinguished. The expected explosion had lesser significance or was not present. By the seismic source parameters analysis, among other things, an estimation of the stress drop in the focus or its size may be determined. The stress drop in the foci of provoked tremors was in the order of 105 Pa and the source radius, according to the Brune’s model, varied from 44.3 to 64.5 m. The results of the three mentioned methods were compared with each other and observations in situ. In all cases the roof falling was forced.

scholarly journals DETERMINING THE PATTERNS OF STABILITY OF MINE WORKINGS FOR CALCULATION ROOF BOLTING PARAMETERS

2021 ◽  
pp. 9-16
Author(s):  
S. Barsukov ◽  
А.Т. Batyrkhanova ◽  
Vladimir Dyomin
Keyword(s):  
Coal Seam ◽  
Longwall Mining ◽  
Practical Significance ◽  
Roof Bolting ◽  
Pull Out ◽  
Deformation Processes ◽  
Mine Workings ◽  
The Stability ◽  
Host Rocks ◽  
Roof Rocks

Purpose.  The published studies are aimed at determining the mechanism of deformation of the rocks of the contour around the workings in terms of the parameters of the emerging fracturing and their dependence on the indicators of the strength of the rocks and the depth of occurrence in the massif. The tasks of the study include the installation of fracture indicators, the determination of the parameters of the development of the deformation process around the working, including the effect of longwall mining and taking into account the possibility of reuse of the workings. Methodology. To solve the set tasks, the method of field observations was used together with the use of regression dependencies to determine the dependences of the parameters on the influencing factors. In addition, the method of full-scale pull-out tests of anchor support was used, which made it possible to determine the clamping forces of the anchors. Originality. In the course of the research, the dependences of stresses and deformation along the K7 coal seam in the conditions of the mine named after Kuzembaev CD JSC "ArcelorMittal Temirtau" for the massif around the mine with fastening. Rational parameters for the use of roof bolting in preparatory mine workings have been established. This type of fastening provides direct contact between rocks and lining. Analysis of the results of calculating the parameters of the roof bolting showed that to maintain the roof in the development workings, it is necessary to take into account the parameters of the roof bolting. The main parameters include the length of the anchors, the total resistance of the roof bolting and the density of the anchors. Anchor support forms laminated rock beams in the roof rocks, which ensure the stability of the workings. Conclusions and practical significance. The results of studies devoted to the establishment of the influence of mining-geological and mining-technical factors on the formation of zones of inelastic deformation in the host rocks were considered. Significant dependences of the deformation processes of rocks in the massif around the workings were obtained, and the parabolic zone of destruction of rocks was determined. The practical significance of the research consists in determining the actual indicators of the required bearing capacity of the anchorage at two levels in the conditions of the development of the coal seam k7 of the Kuzembaev mine.  

SUBSTANTIATION FOR SIMPLIFICATION OF CALCULATION MODELS FOR ASSESSMENT OF THE STABILITY OF ROOF ROCKS

2021 ◽  
pp. 25-36
Author(s):  
Oleksandr Ahafonov ◽  
◽  
Daria Chepiga ◽  
Anton Polozhiy ◽  
Iryna Bessarab ◽  
...  
Keyword(s):  
Differential Equations ◽  
Coal Seam ◽  
Cross Section ◽  
Three Dimensional ◽  
Theory Of Elasticity ◽  
Unit Width ◽  
Distributed Load ◽  
The Stability ◽  
Roof Rocks ◽  
Calculation Models

Purpose. Substantiation of expediency and admissibility of use of the simplified calculation models of a coal seam roof for an estimation of its stability under the action of external loadings. Methods. To achieve this purpose, the studies have been performed using the basic principles of the theory of elasticity and bending of plates, in which the coal seam roof is represented as a model of a rectangular plate or a beam with a symmetrical cross-section with different support conditions. Results. To substantiate and select methods for studying the bending deformations of the roof in the coal massif containing the maingates, the three-dimensional base plate model and the beam model are compared, taking into account the kinematic boundary conditions and the influence of external distributed load. Using the theory of plate bending, the equations for determining the deflections of the coal seam roof in three-dimensional basic models under certain assumptions have a large dimension. After the conditional division of the plate into beams of unit width and symmetrical section, when describing the normal deflections of the middle surface of the studied models, the transition from the partial derivative equation to the usual differential equations is carried out. In this case, the studies of bending deformations of roof rocks are reduced to solving a flat problem in the cross-section of the beam. A comparison of solutions obtained by the methods of the three-dimensional theory of elasticity and strength of materials was performed. For a beam with a symmetrical section, the deflection lies in a plane whose angle of inclination coincides with the direction of the applied load. The calculations did not take into account the difference between the intensity of the surface load applied to the beam. Differences in determining the magnitude of the deflections of the roof in the model of the plate concerning the model of the beam reach 5%, which is acceptable for mining problems. Scientific novelty. To study the bending deformations and determine the magnitude of the roof deflection in models under external uniform distributed load, placed within the simulated plate, a strip of unit width was selected, which has a symmetrical cross-section and is a characteristic component of the plate structure and it is considered as a separate load-bearing element with supports, the cross-sections of this element is remained flat when bending. The deflection of such a linear element is described by the differential equations of the bent axis of the beam without taking into account the integral stiffness of the model, and the vector of its complete displacement coincides with the vector of the force line. Practical significance. In the laboratory, to study the bending deformations and their impact on the stability of the coal seam roof under external loads, it is advisable to use a model of a single width beam with a symmetrical section with supports, the type of which is determined by rock pressure control and secondary support of the maingate at the extraction layout of the coal mine.

scholarly journals RESEARCH OF STATIONARY PLANE FIELDS BY MEANS OF COMPLEX POTENTIAL

2019 ◽  
pp. 39-46
Author(s):  
V. P. Nisonskii ◽  
Yu. V Kornuta ◽  
I. M-B. Katamai
Keyword(s):  
Field Theory ◽  
Complex Variable ◽  
Complex Potential ◽  
Vector Fields ◽  
Oil And Gas ◽  
Water Reservoir ◽  
Singular Points ◽  
Vector Analysis ◽  
Variable Theory ◽  
Complex Variable Theory

Some of the most frequently encountered and generic types of plane vector fields with singular points at the origin of the coordinate system have been studied using complex variable theory methods combined with complex potential methods and field theory methods. The basic concepts of field theory and vector analysis, which are used to study vector fields and the main numerical characteristics of these fields, have been considered. The study of the most frequently encountered vector fields with singular points of four types, namely the generator, the vortical point, the eddy source, the dipole, have been conducted. The application of the complex potential for finding the main characteristics of the vector fields of the considered types, namely their divergence and rotor, has been shown. Equipotential lines and streamlines of the considered vector fields have been obtained and graphically constructed using the method of complex potential. Studied using the vector analysis methods and the methods of the theory of complex variable functions (complex potential) characteristics of vector fields can be used for mathematical modeling of various problems, arising during the study of layers, namely soil and water reservoir filtration problems, as well as in studying the flow of fluid or gas in layers problems. The developed and considered mathematical models of flat vector fields and the found numerical characteristics of these fields can be used to solve other problems of the oil and gas complex, which require studies of the flow of liquids or gases in gas- or oil-bearing beds.

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