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According to the engineering geological characteristics and production technology level of Qianyingzi Coal Mine, the stability control technology of surrounding rock of the cutting roof and pressure relief roadway is proposed. For the advanced section, lagging section and stable section of the mining roadway, technical measures of advanced reinforcement support, side wall protection and lagging temporary support were proposed. Through the real-time monitoring system, the stress of anchor cable and surrounding rock deformation of goaf roadway are monitored, the deformation characteristics of roadway and stope surrounding rock are studied, and the law of mine pressure development in self-formed roadway without coal pillar is revealed by the comparison and analysis with the existing goaf roadway. The results show that the deformation rate of surrounding rock reaches the maximum at the position of 170 m away from the working face, and the deformation of surrounding rock is the most intense at this stage, and then tends to be gentle, and the deformation of surrounding rock reaches the stable stage when the working face lags 220 m. The application effect of the pre-cracking blasting cutting roof for gob-side entry retaining in the W3233 working face of Qianyingzi Coal Mine has reached the expected goal.

To investigate the deformation characteristics and instability mechanism of the transportation hub under downward traversal conditions of the double-track super-large diameter shield tunnel, take the example of Beijing East Sixth Ring Road into the ground reconstruction project. Using the field experimental monitoring method and numerical simulation method, after verifying the accuracy of the model, this manuscript begins to unfold the analysis. The results show that, without any deformation prevention and control measures, The basement raft of the underground structure of the transportation hub will produce a deformation difference of 18 mm, and the tensile stress is more than 1.43 MPa, the inhomogeneous deformation and structural cracking will lead to structural instability and groundwater surges, which seriously affects the safe operation of the transportation hub station. When control measures are taken, the deformation and stress of the base raft slab of the underground structure of the transportation hub are within the prescribed limits, which can ensure the safe operation of the station. The displacement of the base slab of the underground structure in the horizontal direction of the crosssection is all pointing to the east, and the overall trend is to shift from the first tunnel to the backward tunnel. The horizontal displacement of the base slab in the direction of the tunnel axis all points to the beginning of the crossing, and the displacement of the slab in the vertical direction is distributed as "rising in the middle and sinking in the surroundings". For a two-lane super-large diameter shield tunnel penetrating an underground structure, there are two mechanical effects: unloading rebound and perimeter rock pressure. The above deformation characteristics are the superposition effect produced by the two, and this fine assessment of the deformation of the raft foundation provides a scientific basis for formulating the deformation control countermeasures of the crossing project. At the same time, it makes up for the blank of the double-track super-large diameter shield tunnel down through the transportation hub project. [ABSTRACT FROM AUTHOR]

Relevance. Insufficient validity of the quantitative criteria of the regional, local and current forecast of the impact hazard of the coal seams being developed, the absence of algorithms linking the use of geophysical and direct geomechanical methods in forecasting. Aim. To develop a comprehensive method of geodynamic forecasting, including determining the extent of an impact-prone area identified by the results of a regional forecast based on the registration data of the GITS seismic monitoring system, for conducting local and current forecasts of impact hazard by regulatory methods. Object. An array of rocks of the excavation column 4-1-5-7 of the Osinnikovskaya mine during mining operations in the zone of a group of tectonic disturbances and the intersection of advanced workings. Methods. Regional geomechanical forecast by the geophysical method of seismic activity registration (GITS system), local (current) forecast by natural electromagnetic radiation methods (Angel-M equipment) and the output of drilling fines. Results. The paper introduces the results of complex studies in the excavation column 4 1-5-7 of the Osinnikovskaya mine to establish a correlation between seismic activity and the parameters of the stress-strain state of the array. The authors have introduced the concept of integral indicators of the considered parameters IF and Ikσ. They take into account the area of the zone for the i-th range according to the complex parameter of seismic activity F and the coefficient of vertical stresses in the roof of the formation Kσ. It is established that the informative value of the integral indicators is almost twice as high as the informative value of the initial parameters. Experimental nomograms и are presented to determine the category "DANGEROUS/NON-DANGEROUS" for the regional forecast of impact hazard according to the GITS seismic monitoring system. The authors developed a general algorithm for predicting the impact hazard during clean-up operations. This algorithm uses an integrated approach that includes a regional forecast for recording seismic activity within the mine field and local forecasting methods, both geophysical and direct, to clarify the boundaries of seismic energy release zones and confirm the category of impact hazard. Thу paper introduces the example of determining the width of the zone of increased seismic energy release in the mine closest to the seismically active zone. The dynamics of the occurrence, development and decrease of the seismic energy release zone in the considered areas in the mine workings is shown. The authors give the examples of the implementation of a local forecast of impact hazard in previously established potentially dangerous areas by methods of recording natural electromagnetic radiation of rocks and by the output of drilling fines.

A numerical method for modeling the stress-strain state of a rock mass is proposed, taking into account the geomechanical conditions of conducting and maintaining mining under the influence of mining, mining, technical and technological operating conditions of mining schemes for analytical justification of modeling displacements of host rocks around preparatory mine workings. For analytical modeling (determination) of displacements of the host rocks around the preparatory mine workings, the following actions are performed: the geological conditions of the workings are determined, for which a geological section is made indicating the soil and roof rocks; the mechanical characteristics of the rock layers are analyzed; isolines and stress plots are constructed in the vicinity of the treatment workings – ahead of the face, in the work area and in the area of residual reference pressure; the calculation of the zone of inelastic deformations of rocks around the mine is carried out outside the influence of the treatment mine and the plotting of displacement velocities based on experimental observation data under similar conditions in the previous time and the plotting of displacement velocities for the entire service life of this mine, taking into account the established displacements, by generalizing the available experimental data for similar development conditions. [ABSTRACT FROM AUTHOR]

Purpose. The research aims to substantiate the geological principles and peculiarities of modeling complex de-stressing of a stressed bottom-hole mass during the construction of mine workings at depths of more than 1000 m. Methods. A comprehensive research methodology is proposed, which consists of conducting a computational experiment for calculating a complex de-stressing scheme and analyzing the stress-strain state (SSS) of the bottom-hole mass in the most informative mine working cross-sections, conducting experimental studies on the effectiveness of the method using the developed methodology for observing rock pressure manifestations and estimating energy consumption on the tunneling face rock destruction. Findings. A combination of two methods for de-stressing a rock mass adjacent to the tunneling face using advance slots has been substantiated. A geomechanical model has been created that takes into account the specifics of the proposed method. The stress-strain state of the rock mass adjacent to the tunneling face has been calculated in a series of cross-sections and longitudinal section of mine working. Originality. Three geotechnological principles of simultaneous de-stressing of both rocks adjacent to the face and rocks within the mass along the mine working route has been formulated and elaborated, embodied in the construction of a geomechanical model of complex adjacent rock mass de-stressing. Based on the obtained stress-strain state, five positions of have been developed for complex consideration of changes in the distribution fields of determining stress components. The methodological principle for assessing energy consumption for rock destruction has been substantiated, and an evidence base has been created to confirm the advantages of the proposed mine working construction technology at depths above 1000 m in a gas-dynamically active rock mass. Practical implications. The method for complex de-stressing the rock mass adjacent to the tunneling face, using pre-drilled wells and de-stressing slots, is proposed. Experimental studies confirm the proposed method feasibility in three directions for safe and resource-saving construction of mine workings in a gas-dynamically active rock mass at great depths. Calculations have proven that energy consumption for bottom-hole rock destruction has decreased in the range of 15-26%. [ABSTRACT FROM AUTHOR]

The article describes two single-mass models of a drill string and different methods of bottom-hole treatment: percussion and rotary percussion. The loads created by the piston are transferred to rocks via a progressively advancing bit in the first model and via a rotatable bit in the second model. The drag force applied to the bit is found from the nonlinear dependence on the penetration rate and kinematic parameters which govern the force impact on the rock and its loss of strength: initial blow velocity and rotational speed modulus of the bit. The optimal initial blow velocities are found at the preset blow frequency; they ensure elimination of short-term stick slips in penetration of the bit. For the mentioned cases of penetration, the processes of percussion and rotary percussion drilling in strong rocks are provided with the strict mathematical description. The numerical modeling results are presented. [ABSTRACT FROM AUTHOR]

The mine shafts in the salt (unwatered) rock mass at the Upper Kama deposit are mostly lined with cast-in-place concrete and reinforced concrete, which should ensure the required load-bearing capacity and water impermeability in host rocks in creep. The long-term observations of the shaft lining in operation revealed some typical patterns of failure induced by the rheological properties of salt rock mass under the action of rock pressure. The technical evaluation of the lining and reinforcement of mine shafts is an integrated checkup procedure including measurements of fractures and areas of corrosive zones/rock falls; updating of actual geometrics of lining from laser measurements; determination of residual strength of lining; mathematical modeling; estimation of integral reliability index of lining. The authors propose a procedure to categorize technical conditions of concrete lining in mine shafts in operation in salt-bearing rock mass in creep. The application of the procedure is described, and the conclusions on the package of repair activities are drawn. [ABSTRACT FROM AUTHOR]

Purpose. The research aims to substantiate the technological solutions to ensure the rock mass stability through a rational approach to strengthening the zones of increased rock pressure behind the longwall face. Methods. To achieve the purpose set, a complex research method is used, which includes an analysis of practical experience in mining medium-thickness flat-lying coal seams, a study of the stress-strain state of rocks above the coal mass marginal area, and mine research into the influence of mining-technical factors on the state of zonal preparatory workings. Findings. The patterns of stress influence on the mine working stability have been determined depending on the miningtechnological parameters of mining operations. Empirical dependences of the stress influence on the mine working stability have been revealed. The parameters of stress influence on the mine working stability have been found depending on the mining-technological parameters of mining operations. Originality. The conducted research made it possible to determine the degree of influence of mining-technical conditions of mining operations on deformations in border rocks with various types of support in extraction workings, which helps to understand the dynamics of deformation processes occurring in the coal-rock mass surrounding mine workings maintained behind the longwall face. Practical implications. The revealed deformation patterns can be used in calculating the rock pressure manifestations when conducting mine workings on deep levels under various mining-technical conditions of mining operations, which has practical significance for ensuring the stability and safety of maintaining mine workings at the stage of mining operations. The use of roof-bolt support is proposed as an effective means not only to ensure stability, but also to maintain safe operating conditions in mine workings. [ABSTRACT FROM AUTHOR]

The optical polarization method with ring-shaped photoelastic sensors, digital photography of isochromatic patterns and their clarification using neural networks is developed for the stress measurement in rock mass. The case-studies of the photoelasticity application in solving various problems of elasticity and rock pressure analysis are reviewed. As a result of a lab-scale experiment, a data set of 15000 isochromatic images is collected. The machine learning algorithm was a convolutional neural network, the Inception module. The authors recommend using downhole sensors for the continuous stress monitoring in underground mines and integrating the obtained data in a digital model with the help of IoT. [ABSTRACT FROM AUTHOR]

The article describes the studies on permeability of coal cores with a through drainage fracture with and without a monolayer of a proppant. The experimental procedure is descried. The parameters of the jointed structure of test long-flame coal are given. The efficiency of wedging drainage fractures by a sparse proppant monolayer in building up permeability of deep-seated coal is demonstrated. [ABSTRACT FROM AUTHOR]

The study focuses on the connection between two processes: deformation of proppant under the action of rock pressure and the rock pressure change after injection pressure release. The modeling of proppant deformation (mechanics of granular medium) uses the discrete element method, and the rock pressure redistribution (rock mechanics) is modeled using the earlier developed model of rock as a medium with internal energy sources and sinks, and the finite element method. The numerical modeling shows that depending on the loading history and on the rock mass properties, the mode of deformation can be both stable and unstable. For the stable mode of deformation, the pressure balance is calculated at the created fracture boundary, and the change in the proppant porosity is estimated. In the unstable mode, rock mass experiences dynamic events induced by rock pressure. [ABSTRACT FROM AUTHOR]

During the underground mining of coal resources, the rock pressure emerges acutely and the mine geological disasters occur frequently. It is of great significance to grasp the manifestation law of rock pressure in time to guide the safety production and operation in the pit. In this research, the calculation equations and concept of information entropy based on zone safety degree are primarily defined, and the synergetic theory of the maximum information entropy principle is combined to put forward the synergy prediction model of information entropy based on zone safety degree. In the meantime, the synergy prediction model of information entropy based on zone safety degree is employed to calculate and predict the first weighting step and the periodic weighting step of the main roof of the 9203 working face of Hengsheng Coal Mine in China's Shanxi Province, as well as verifying the validity and reliability of the synergy prediction model of information entropy based on zone safety degree by the comparison of similar simulation test results, which has presented a scientific basis for the effective control of rock pressure and roof management. [ABSTRACT FROM AUTHOR]

When excavating in composite strata, the wear rate of the disc-cutters and the frequency of abnormal wear will significantly increase. Therefore, the overcut clearance is accordingly reduced, which results in the occurrence of shield jamming accidents. In order to analyze the influence of shield attitude deflection and longitudinal non-uniform distributed overcut on the mechanical properties of shell, based on Baiying section on Shenzhen metro line 13, the rock pressure exerting on shield machine during construction stage was calculated by FLAC 3D. The results indicate these as follows. Severe eccentric wear occurred at the jamming section. The maximum wear reaches 25 mm. The operational parameters encounter obvious fluctuation in composite strata. The shield machine has a higher tendency to deflect upwards. In upper soft and lower hard strata, the rock pressure borne by the upper part of the shield shell is larger than which on the lower part. The stress concentration occurs at the interface between the strata. The stress at front of the shield shell grows more significantly, compared with which at the shield tail. The normal pressure at the tunnel vault and invert respectively increases, when the shield deflects upward and downward. The upward deflection is more likely to cause jamming accident compared to the downward deflection. The friction suffered by shield shell rises rapidly when the deflection angle exceeds ± 0. 5°. During shield tunneling, the shield machine should maintain a horizontal or small angle downward deflection state as far as possible. [ABSTRACT FROM AUTHOR]

On the working face below shallow and close coal seams, there are residual pillars. The mine's ability to operate safely is constrained by the coal pillars' vulnerability to sudden instability and powerful ground pressure disasters during withdrawal. This paper uses the 31,106 working face of the Huoluowan coal mine as its research backdrop and employs field observation, theoretical analysis, and numerical simulation to examine the strong dynamic load mechanism of the overlying coal pillars. According to the analysis, the residual pillar's stress diffusion angle is 29 degrees after mining the working face above it, which has an impact on the main roof's stability above the working face's retracement roadway. The main roof is impacted by the excavation disturbance and the remaining pillars during the working face's final mining phase, displaying a complex stress superposition state. The retracement roadway is significantly deformed as a result of the plastic zone of the surrounding rock changing from small-scale damage to extensive damage. The proposed "hydraulic roof cutting + reinforcement support" prevention technology is based on the prevention idea of weakening important rock strata, changing the stress transmission path, and strengthening adjacent rock. Field testing shows how hydraulic fracturing reinforces the roof structure, lessens the heavy dynamic load on the supporting pillars of overlying residual coal, reduces rock deformation in the retracement roadway, and ensures the stability of the working face during withdrawal. The study's findings are significant for the secure removal of a working face under similar circumstances. [ABSTRACT FROM AUTHOR]

Copyright of Inzynieria Mineralna is the property of Polskie Towarzystwo Przerobki Kopalin and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The main purpose of mine workings is the exploitation of ores and minerals that are used in different aspects of life. The most common underground method all over the world is the longwall mining method. The increasing demand for minerals and ores and the difficult mining conditions at greater depths make the longwall mining system a good candidate in mining. The equilibrium condition is disrupted when the longwall face advances, and as a result, the surrounding rocks eventually fracture and cave. Moreover, the induced pressure due to caving or fractures of the immediate roof rocks and the tilting of the main roof exerts an excessive load on the hydraulic supports in the longwall faces. Induced disturbances of the overburden rocks must be thoroughly investigated since this will enhance our understanding of rock pressure and ground control. The main objectives of this paper are to review the importance of the longwall mining system as an exploitation method and its applications around the world. as well as the main factors affecting the stability of supports in longwall faces, especially hydraulic supports. From this study, it can be seen that the most important technical factor that affects face stability is the rate of face advance. In addition, the significant natural factors affecting the stability of workings are roof conditions and the geometry of the panel.

During the underground mining of coal resources, the rock pressure emerges acutely and the mine geological disasters occur frequently. It is of great significance to grasp the manifestation law of rock pressure in time to guide the safety production and operation in the pit. In this research, the calculation equations and concept of information entropy based on zone safety degree are primarily defined, and the synergetic theory of the maximum information entropy principle is combined to put forward the synergy prediction model of information entropy based on zone safety degree. In the meantime, the synergy prediction model of information entropy based on zone safety degree is employed to calculate and predict the first weighting step and the periodic weighting step of the main roof of the 9203 working face of Hengsheng Coal Mine in China’s Shanxi Province, as well as verifying the validity and reliability of the synergy prediction model of information entropy based on zone safety degree by the comparison of similar simulation test results, which has presented a scientific basis for the effective control of rock pressure and roof management.

In the process of underground mining of deep levels rock pressure can appear in any form, creating a serious threat to the lives of miners, disrupting the normal course of mining works and reducing the efficiency of mining production. The solution of the problem of rock pressure control becomes very urgent for underground mines developing vein deposits at a depth of more than 250 m. The aim of the study is the development and justification of mining methods to provide safe and efficient mining of deposits in complicated mining and mechanical conditions. In this paper, the factors of redistribution and dangerous concentration of stresses in the mined ore mass were identified, the methods of rock mass management in complicated geotechnical conditions were studied, and their advantages and disadvantages were revealed. It was determined that the sublevel stoping with the combined use of existing methods of rock pressure control and applying selfpropelled mining machinery is currently one of the most promising method finding widening application scope. In the context of Zarmitan gold ore zone the options of technological schemes of the sublevel stoping method were considered, providing for a combination of different methods of rock pressure control, allowing to minimize the disadvantages of one method through using the advantages of other ones. We proposed sublevel stoping options with artificial polygonal pillars and with artificial columnar pillars, which allowed to reduce ore losses in inter-stope pillars, arch pillars, and secondary dilution. In addition, artificial pillars, taking compressive/tensile stresses, prevent their concentration and create safe conditions for extraction at adjacent and underlying levels.

This paper aims to clarify the mechanism of the longitudinal response of a tunnel under normal faulting via a comprehensive analysis of available experimental data and numerical simulations. Four 1 g condition model tests were reviewed and reanalysed to highlight the key characteristics of the tunnel response under normal faulting: S-shaped deformation and inverted S-shaped bending strain distribution in the longitudinal direction; the main affected zone of faulting is approximately six times the tunnel diameter to the fault plane. A threedimensional finite element model was also established and verified, followed by a sensitivity analysis of key parameters, including the fault dislocation, dip angle, tunnel rigidity and relative stiffness between the hanging wall and footwall. All results reveal that the longitudinal mechanical response under normal faulting is dominated by a combination of bending, tension, and shearing. Bending and shearing are induced by the large unbalanced rock pressure at the vault in the hanging wall and the inverted arch in the footwall; the value of unbalanced rock pressure is directly proportional to the dislocation but negatively correlated with the dip angle. Although the main part of the tunnel stays in tension, axial compressive strain exists around the fault plane when the dip angle is greater than 70, which may be related to the ovaling effect of the tunnel. Such an ovaling effect is caused by the compression at the cross-section of the tunnel and may lead to more complicated internal strain. [ABSTRACT FROM AUTHOR]

The paper deals with an electrical design of an electrohydraulic system, which is capable to use for rock pressing. The system has three stations, which controlled by programmable logic controller. The electrical design contains the wiring, and the development of a valve controller card, which provides adequate current to a pressure relief valve. [ABSTRACT FROM AUTHOR]

Based on the coal mine engineering, the mechanical model with the horizontal forms of bedrock intrusion is established, and the characteristics of in-situ stress distribution in the intrusion area are analyzed. The numerical model is built based on FLAC3D, and the distribution and influence law of stress field, deformation field, plastic zone of surrounding rock of roadway and advance abutment pressure in face caused by rock intrusion are analyzed. The results show that the stress concentration coefficient of the geo-stress increases with the decrease of the elastic modulus ratio of coal and rock, and increases with the increase of the thickness of the bedrock. The stress concentration degree of the surrounding rock of the roadway invaded by the bedrock is obvious, and the coal and rock mass are easy to be destroyed by compression and shear, which is very disadvantageous to the stability of the roadway, the distribution of shear plastic zone of roadway surrounding rock invaded by sill is wider. As the face is close to the bedrock invasion area, the influence of bedrock invasion on the distribution of advance abutment pressure is gradually increased, and the characteristics of stress mutation gradually appear, which is unfavorable to the stability of surrounding rock.

This paper focuses on the modeling of a sedimentary basin where the exploration of oil and gas takes place. In the modeling, we calculate the vertical variation of pore and rock pressure, which serve as natural pumps for the accumulation of fluids, where we use post-migration surface seismic data and information as necessary. We compare two methods of pore pressure calculation. In the first case, we calculate stress due to vertical loading created by gravitational geological overburden. In the second case, we propose a more complex method to calculate the stress distribution based on the mechanics of solids under gravity loading, using the concept of the first tensor invariant and the linear behavior of Hooke's law. We prove the use of the P and S velocities and density information to calculate rock, pore, and effective pressure distribution, useful for characterizing potential zones for oil and gas accumulation. The proposed method allows formulation of rock pressure from different calculations instead of as a simple overburden pressure value. The joint analysis of the calculated sections can be used to identify patterns and correlations, outline and characterize the target zones, and make practical geological conclusions. [ABSTRACT FROM AUTHOR]

Abstract This paper focuses on the modeling of a sedimentary basin where the exploration of oil and gas takes place. In the modeling, we calculate the vertical variation of pore and rock pressure, which serve as natural pumps for the accumulation of fluids, where we use post-migration surface seismic data and information as necessary. We compare two methods of pore pressure calculation. In the first case, we calculate stress due to vertical loading created by gravitational geological overburden. In the second case, we propose a more complex method to calculate the stress distribution based on the mechanics of solids under gravity loading, using the concept of the first tensor invariant and the linear behavior of Hooke’s law. We prove the use of the P and S velocities and density information to calculate rock, pore, and effective pressure distribution, useful for characterizing potential zones for oil and gas accumulation. The proposed method allows formulation of rock pressure from different calculations instead of as a simple overburden pressure value. The joint analysis of the calculated sections can be used to identify patterns and correlations, outline and characterize the target zones, and make practical geological conclusions.

The deterioration of rock mass and shotcrete lining has major consequences on the long-term performance of tunnels in the weak rock mass. In this study, the long-term behavior of rock mass and shotcrete in tunnels was simulated by using the three-dimensional finite difference method, considering the nonlinear deterioration mechanism. The degradation of rock mass was simulated by weakening the mechanical parameters, while the deterioration of shotcrete was modeled by decreasing the thickness. The support pressure, internal force, and displacement of the secondary lining were monitored with the gradual degradation of rock mass and shotcrete. As a consequence, the factor of safety (FoS) evolution with time was discussed. The results indicated that 1) the deterioration of both rock mass and shotcrete would significantly increase the rock pressure on the secondary lining, leading to an increase in the displacement (0–14 mm). The FoS of the secondary lining was reduced by 85%. 2) The influence of shotcrete’s deterioration on the secondary lining was relatively less, and the rock pressure on the secondary lining increased from 0 kPa to 13.8 kPa. The long-term safety of the tunnel is remarkably affected by the deterioration of rock mass, depending on the deterioration characteristics of the rock mass. Therefore, the deterioration characteristics of rock mass should be fully considered in tunnel maintenance.

On the working face below shallow and close coal seams, there are residual pillars. The mine’s ability to operate safely is constrained by the coal pillars’ vulnerability to sudden instability and powerful ground pressure disasters during withdrawal. This paper uses the 31,106 working face of the Huoluowan coal mine as its research backdrop and employs field observation, theoretical analysis, and numerical simulation to examine the strong dynamic load mechanism of the overlying coal pillars. According to the analysis, the residual pillar’s stress diffusion angle is 29 degrees after mining the working face above it, which has an impact on the main roof’s stability above the working face’s retracement roadway. The main roof is impacted by the excavation disturbance and the remaining pillars during the working face’s final mining phase, displaying a complex stress superposition state. The retracement roadway is significantly deformed as a result of the plastic zone of the surrounding rock changing from small-scale damage to extensive damage. The proposed “hydraulic roof cutting + reinforcement support” prevention technology is based on the prevention idea of weakening important rock strata, changing the stress transmission path, and strengthening adjacent rock. Field testing shows how hydraulic fracturing reinforces the roof structure, lessens the heavy dynamic load on the supporting pillars of overlying residual coal, reduces rock deformation in the retracement roadway, and ensures the stability of the working face during withdrawal. The study’s findings are significant for the secure removal of a working face under similar circumstances.

The main purpose of mine workings is the exploitation of ores and minerals that are used in different aspects of life. The most common underground method all over the world is the longwall mining method. The increasing demand for minerals and ores and the difficult mining conditions at greater depths make the longwall mining system a good candidate in mining. The equilibrium condition is disrupted when the longwall face advances, and as a result, the surrounding rocks eventually fracture and cave. Moreover, the induced pressure due to caving or fractures of the immediate roof rocks and the tilting of the main roof exerts an excessive load on the hydraulic supports in the longwall faces. Induced disturbances of the overburden rocks must be thoroughly investigated since this will enhance our understanding of rock pressure and ground control. The main objectives of this paper are to review the importance of the longwall mining system as an exploitation method and its applications around the world. as well as the main factors affecting the stability of supports in longwall faces, especially hydraulic supports. From this study, it can be seen that the most important technical factor that affects face stability is the rate of face advance. In addition, the significant natural factors affecting the stability of workings are roof conditions and the geometry of the panel. [ABSTRACT FROM AUTHOR]

Purpose. Increasing the load-bearing capacity of metal arch supports used to maintain the mine workings due to strengthening in places with the highest bending moment. Methods. The stress-strain state of the rock mass and support is analyzed using the ANSYS software package. The problem is studied in three variants: a support without strengtheners, a support with one strengthener in the area with the maximum bending moment, and a support with three strengtheners in the areas with the highest bending moments. To determine the bending moments and normal forces in a three-section metal arch support, the finite element method is used for specific and existing conditions, which is followed by the selection of the required standard size of the support. Findings. The conducted research gives reasons to believe that the proposed variant for increasing the load-bearing capacity of the support, made from a special replaceable rolled profile (SCP), can significantly improve the state of mine workings. Obviously, the proposed solution can be applied not only to arch supports, but also to other structures of rolled metal support. Originality. The pattern of changes in the values of internal forces arising in metal arch frame supports, depending on the deformation characteristics, the location of the strengtheners, as well as on the geometric characteristics of the mine working and the ratio of lateral and vertical loads on the support, has been determined. Practical implications. The proposed variant for increasing the load-bearing capacity of the support can be used to sustainably maintain mine workings in difficult mining-geological conditions of the Karaganda Coal Basin mines. [ABSTRACT FROM AUTHOR]

After the engineering rock mass has been affected by comprehensive effects of mining and disturbance, it experiences an input of external energy as well as dissipation and release of internal energy. From the viewpoint of energy, characteristics of rock failure are studied, and the law of rock unstable deformation and energy evolution is analyzed. The damage mechanism of rock is revealed easily. A gradual loading and unloading test of fractured rock is carried out to analyze deformation characteristics of the fractured rock during the load- -bearing process, and to study the law of energy dissipation and release under different load- ing and unloading stress levels. The results show that: (1) the load-bearing time, loading and unloading stress level, stress at crack initiation and peak stress of fractured rock gradually decrease with an increase in the number of cracks, and the descending speed decreases grad- ually with the increase in the number of cracks; (2) the strain at crack initiation and peak strain of the fractured rock increase gradually with an increase in the number of cracks, and the gathering speed decreases with the increase of the number of cracks; (3) the released strain energy and dissipation energy of fractured rock increase with an increase of loading and unloading stress levels, and the increasing rate gradually slows down; (4) the number of acoustic emission events is positively related to the degree of rock damage, and the increase in the number of cracks will prolong duration of the number of acoustic emission events. The results have a theoretical value for energy evolution and deformation damage of fractured rock masses, and also provide experimental experience to study the instability precursor information of rock materials from the viewpoint of energy. [ABSTRACT FROM AUTHOR]

At different stages of oil and gas field development, a reservoir undergoes various stress-strain states. The change of reservoir pressure during development results in the change in physical and mechanical properties of the reservoir. In terms of geochemistry, the fluids also affect the properties of the host rocks. The process of reservoir fluid extraction can clog flow channels with washed-out rock particles and deposited paraffins and salts, but also decrease the strength and elastic characteristics of the rock. The article provides a brief analysis of operations affecting the causes of changes in the physical, mechanical, porosity and permeability properties of formations during drilling and oil-field development. The method of theoretical calculation of changes in the formations’ porosity and permeability is provided. To establish the convergence of theoretical calculation methods with real data, the tests to determine the uniaxial compressive strength and the filtration experiments on terrigenous samples of a West Siberian field were carried out. Water and kerosene in different proportions were used as saturating fluids in the experiment to determine physical and mechanical properties. Based on the data obtained, the dependencies of the modulus of elasticity and the uniaxial compressive strength on different types of saturation were derived, with diagrams and calculating formulas given. In the filtration experiment, the influence of effective pressure on permeability of samples at volumetric compression was determined. The dependencies of permeability decline on the sample axial load were established. The obtained dependencies can be used to work out geological and engineering procedures for well stimulation and field development management during the entire operational life cycle.

Purpose. The purpose of the study is to justify the conditions of stability and features of manifestations of rock pressure on the circuit of local preparatory workings with different methods of protection in deep mines. Research Methods. An integrated approach is used, including analysis and generalization of theoretical and experimental studies on the problem of the stability of excavation preparatory workings, with different methods of protection, in mines developing steeply and steeply bedded layers at great depths. Results. As a result of the experimental and analytical studies, it was found that when guarding haulage drifts by compliant security structures (rolling fires from wooden sleepers), the load on the lining of the preparatory mine over time, as the lava moves, tends to a finite value in hyperbolic dependence. In this case, there is a change in its growth, and the displacements of the lateral rocks on the contour of the recoil drift take the greatest values in the initial period of time after coal extraction. However, when protecting the production by fragile security structures, the pillars of coal, a change in the load growth on the lining per unit time occurs according to a linear law, which leads to a deterioration in the stability of the recoil drift behind the face, associated with the loss of the bearing capacity of the lining, designed to support the preparatory development. Scientific novelty. The stability conditions of the recoil drift are based on the representation of the lining installed in the excavation excavation, in the form of a geometrically unchanged system, individual elements of which experience bending deformations from the action of external forces that appear when unloading the coal-bearing massif as a result of mining operations. Practical significance. To improve the safety of miners in deep mines, it is necessary to use compliant structures or laying out worked out space to protect recoil drifts, based on increasing their stability, which ensures their operational state behind the face.

Copyright of Mining of Mineral Deposits is the property of Dnipro University of Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Mining of Mineral Deposits is the property of Dnipro University of Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The purpose of this research is to study the area near the bottom of the hydrocarbon well, which is usually affected by drilling and development operations, and to find a modern method that improves the transfer of fluid from the reservoir to the well. The area near the wellbore of an oil and gas formation is a very active and unstable zone. Field studies have shown that during the process of drilling the first well into the pay zone, a new area of disturbed permeability and porosity forms around the wellbore. This disturbed area is called the skin zone and is characterized by different properties. The skin zone can also form during the completion processes of hydrocarbon wells. In terms of well test processing for any hydrocarbon well, the term "skin effect" should be understood as the effect of changes in the lower wellbore zone (i.e., changes in rock properties, changes in formation fluid, formation structure, geologic section, etc.) on bottom wellbore pressure. This indicates a change in the permeability of the bottom zone of the borehole during drilling and development. In this paper, a new computational method is proposed in which the investigation of hydrocarbon well condition can be performed in two ways. The first way represents replacing the true radius of the wellbore (rw) with an effective radius (rwe). Under this condition, the skin factor term reflects only the effect of changes in the bottom wellbore zone. The second way is that the skin factor indicates not only the amount of change in the bottom wellbore zone, but also the effect of hydrodynamic imperfection of the hydrocarbon well performance during production, while maintaining the value of the well radius. After evaluating these parameters, it is possible to conclude the effectiveness of the implemented measures in the bottom wellbore zone of the formation. At the same time, the value of the skin factor after the performed works regarding the impact on the bottom zone can determine the positive or negative impact on the operation of the hydrocarbon well. [ABSTRACT FROM AUTHOR]

This paper describes some numerical experiments for stress modeling in the zone around a reservoir in a sedimentary basin, where oil and gas exploration is real or potential. We aim to map mainly low- and high-pressure zones, under the principle that they act as push-and-pull natural pumps for fluid accumulation. The necessary data for practical work is based on seismic data, as a post-migration process with the knowledge of velocities of the P and S waves, and the density information. The computation is designed for simple geometries to represent a reservoir geology, and it is addressed as a boundary value problem (BVP) involving the Beltrami-Michell's partial differential equation with Dirichlet conditions. The method employed was the Green's function expressed by Fourier series for the solution of the BVP, where the boundary conditions are given by the stress components along the boundary of the target volume. The first stress invariant controls the elastic mechanical behavior of the subsoil; therefore, once the distribution of rock pressure is obtained, and the boundary conditions are defined, solving the BVP allows the calculation of the stress components distribution (normal and tangential) within a separate target volume for details. The relationship between rock pressure and stress components is established by the Beltrami-Michell problem, which takes the form of a Poisson's equation. The proposed method was applied in a more complex target zone present in the Marmousi model, which contains reservoirs within regions of interest, expanding to more realistic complex problems. [Display omitted] • The low- and high-pressure zones act as natural pumps for fluid accumulation. • The first stress tensor invariant rules the subsoil elastic mechanical behavior. • The Beltrami-Michell equation relates rock pressure and stress tensor components. • The Beltrami-Michell solution is closely related to stress boundary conditions. • The Poisson's ratio values can cause deviations in the expected solution. [ABSTRACT FROM AUTHOR]

The features of originating load on “support-interframe shield” system in the process of formation of broken rock zone around a mine working were investigated by laboratory tests on models of equivalent materials and structural models. The role of interframe shield in the formation of frame support load has been revealed. It was found that a natural self-supporting arch is formed over interframe shields within the broken rock zone, which redistributes the load on the roof support frames, while the weight of rocks within the arch puts pressure on the interframe shields. The requirements for interframe shield of frame supports in mine workings have been developed.

The findings of review of promising methods and techniques providing increasing effectiveness of degassing of coal seams containing methane in the process of their underground mining are presented. Based on the review findings, traditional methods and techniques of degassing were identified, the effectiveness of which is 12–25 %, as well as unconventional methods providing methane degassing of up to 40%. As a classification feature of the unconventional methods and techniques of gaseous methane liberation, a condition of decreasing pressure and increasing temperature of coal matrix containing solid gas hydrate has been adopted. The conditions for methane transition from gas hydrate to free gas taking into account actual mining and technogenic conditions of the mines have been identified. Given the difficulty of supplying additional thermal energy into a coal seam, as the main way to reduce pressure in the seam, unloading of the rock mass relative to the initial stress state, and disruption of coal and rocks in the course of transition from their elastic deformation to elastic-plastic and out-of-limit deformation are accepted.

Copyright of Scientific Bulletin of National Mining University is the property of National Mining University, State Higher Educational Institution and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The aim of this research is to study the stability of haulage drifts and the manifestations of rock pressure in them lengthwise the working area when protecting them with coal pillars. To assess the stability of workings, field experiments were conducted to study the manifestations of rock pressure in the haulage drifts of a steep coal seam. It has been registered that as the breakage face progresses, the displacement of roof rocks on the contour of the drift linearly increases with an increase in the length of the working area. The deformation properties of coal pillars were studied taking into consideration the extent of the convergence of the roof and soil. This paper reports a theoretical model that describes the destruction of the above-drift coal pillars when unloading the coal-bearing massif that hosts the workings. It has been determined that the equilibrium state of coal pillars is ensured when the specific deformation and stress potentials are equal before the occurrence of main cracks of destruction. As the relative deformation of coal pillars increases at compression, when this equality is broken, the specific energy intensity of destruction increases. It is noted that at a distance exceeding l>10 m behind the breakage face, the occurrence of the main cracks of destruction is followed by a stability loss in the coal pillars. As a result of external forces, the change in the volume and shape of the coal pillars causes the intensification of the process of convergence of lateral rocks on the contour of haulage drifts lengthwise the working area and leads, with a certain degree of probability, to a deterioration in the stability of workings. The results of this study could be used to justify the choice of technique to protect haulage drifts. This would allow the timely development of minefield reserves thereby improving the safety of operations. It is recommended that the technique of protecting haulage drifts by coal pillars should be abandoned [ABSTRACT FROM AUTHOR]

Rock pressure around the contour of horizontal mining works, has different values which are variable in time. Periodic rising of deformations on the supporting structure is corelated with gradual rising of rock pressure, which we will call primary pressure. As soon as the opening deformation stops, the primary pressure turns into secondary pressure. Both primary pressure and secondary pressure, show certain particularities which we will analyze in depth in this study. [ABSTRACT FROM AUTHOR]

In this paper we will analyze the deformation way for horizontal mining works executed in deep sedimentary rocks, at Petrila Mining Exploitation. These studies were possible through the deployment of monitoring stations for rock pressure and rock movement on work contour, which led to determining of deformation speed and mining work convergence in deep sedimentary rocks. The deformations were detected by these stations deployed at horizon 100 and 150. [ABSTRACT FROM AUTHOR]