Coal Mine Roadways Research Articles

Accurate integrated position measurement system for mobile applications in GPS-denied coal mine

The automatic positioning of underground mobile applications plays a crucial role in enabling intelligent coal mining. However, due to the diverse kinematics and dynamics of these applications, various positioning methods have been proposed to match different targets. Nonetheless, the accuracy and applicability of these methods still fall short of meeting the requirements for field applications. Based on the vibration characteristics of underground mobile devices, a multi-sensor fusion positioning system is developed to enhance the accuracy of positioning in long and narrow global positioning system denied (GPS-denied) underground coal mine roadways. The system combines inertial navigation (INS), odometer, and ultra wide band (UWB) technologies through extended Kalman filter (EKF) and unscented Kalman filter (UKF). This approach enables accurate positioning by recognizing target carrier vibrations and facilitating fast conversion between multi-sensor fusion modes. The proposed system is tested on both a small unmanned mine vehicle (UMV) and a large roadheader, demonstrating that UKF enhances stability for roadheaders with strong nonlinear vibrations while EKF is more suitable for flexible UMVs. Detailed results confirm that the proposed system achieves an accuracy level of 0.15 m, meeting most coal mine application requirements.

Study on Stress Disturbed Mechanism and Supporting Method of Weakly Cemented Roadway near Chambers

After excavation of the weakly cemented roadway adjacent to the chambers, deformation characteristics such as roof subsidence, roadway extrusion, and floor heave appear, showing the characteristics of large deformation of surrounding rock, long deformation duration, and serious damage, which are not conducive to guaranteeing safety mining. Based on the technical means of the rock mechanical property test, mineral composition analysis, in situ stress test, and surrounding rock deformation monitoring of 2# coal roadway in Hongqingliang coal mine, a numerical simulation study on the influence of surrounding rock stress on adjacent chamber groups was carried out. The physical and mechanical properties of the weakly cemented rock were obtained, the stress distribution law of the 2# coal roadway was mastered, the deformation characteristics of the surrounding rock of the weakly cemented roadway were obtained, and the deformation and failure mechanism of the weakly cemented roadway adjacent to the chambers were revealed. The relationship between the regional stress increment of the chambers and the failure range of the surrounding rock of the roadway is revealed, establishing a mechanical model of allowable deformation + stress release + controlled form with U-shaped steel as the main structure. The roadway support countermeasures were given and applied in engineering practice.

3D LiDAR Point Cloud Registration Based on IMU Preintegration in Coal Mine Roadways

Point cloud registration is the basis of real-time environment perception for robots using 3D LiDAR and is also the key to robust simultaneous localization and mapping (SLAM) for robots. Because LiDAR point clouds are characterized by local sparseness and motion distortion, the point cloud features of coal mine roadway environments show a weak texture and degradation. Therefore, for these environments, the traditional point cloud registration method to register directly will lead to problems, such as a decline in registration accuracy, z-axis drift, and map ghosting. To solve the above problems, we propose a point cloud registration method based on IMU preintegration with the sensor characteristics of LiDAR and IMU. The system framework of this method mainly consists of four modules: IMU preintegration, point cloud preprocessing, point cloud frame matching and point cloud registration. First, IMU sensor data are introduced, and IMU linear interpolation is used to correct the motion distortion in LiDAR scanning, and the IMU preintegration error function is constructed. Second, the point cloud segmentation is performed using the ground segmentation method of RANSAC to provide additional ground constraints for the z-axis displacement and to remove the unstable flawed points from the point cloud. On this basis, the LiDAR point cloud registration error function is constructed by extracting the feature corner points and feature plane points. Finally, the Gaussian Newton solution is used to optimize the constraint relationship between the LiDAR odometry frames to minimize the error function, complete the LiDAR point cloud registration and better estimate the position and pose of the mobile robot. The experimental results show that compared with the traditional point cloud registration method, the proposed method has a higher point cloud registration accuracy, success rate and computational efficiency. The LiDAR odometry constructed using this method can better reflect the authenticity of the robot trajectory and has higher trajectory accuracy and smaller absolute position and pose error.

Study on mechanical characteristics of anchor drilling rig group for rapid excavating

Aiming at the imbalance problem of excavating and anchoring efficiency ratio in the underground coal mine, a new type of parallel operation unit of excavation-supporting-anchoring is proposed to improve the excavating efficiency. Considering the uneven factors of the roof and floor of the coal mine roadway, the influence of different drilling angles and leg support angles on the leg support force is studied under the condition of simultaneous drilling of multiple drilling rigs. The results show that the maximum support force is 4.002 KN when the leg angle is different and the drilling angle is different. By constructing the coupling vibration model of the multi-drill drilling process and using the Lagrange method to solve the vibration law of key components of the anchorage system, the vibration law of drill pipe under different influencing factors such as cantilever extension, multi-drill simultaneous drilling, and drilling incident angle is studied. The results showed: (1) The vibration of the drill pipe in the cantilever extension state is more severe than that in the retracted state, and the maximum vibration peak reaches 7.61 mm. (2) The vibration response of the drill pipe is the most intense under the condition of four top anchor drilling rigs drilling at the same time. Under the working condition of only two drilling rigs, the vibration response of the drill pipe is the smallest. (3) As the drilling angle of the drilling rig increases, the vibration response of the drill pipe is more severe and the vibration amplitude is larger. A test prototype is built to simulate the actual anchoring drilling process, and the vibration law of the support platform and the drilling rig is obtained through the vibration detection system. The test results show that the vibration law of the key components is approximately the same as the theoretical simulation results. The relevant theoretical results can provide a technical basis for the drilling stability of the anchoring system.

Research on main influencing factors and complete support technology for dynamic pressure and large deformation roadway

To determine the main factors influencing dynamic pressure and large deformation roadways, a targeted set of support technologies was designed. The 2603 air inlet roadway of the Zhangcun coal mine in Lu'an, Shanxi Province, was taken as an example. The influence of the Wenwangshan South normal fault and in situ stress field on the dynamic pressure roadway was analyzed theoretically, and the main factors influencing this dynamic pressure and large deformation roadway under natural geological conditions were determined. The effect of the existing roadway support scheme was evaluated by field test methods such as nondestructive bolt testing. The influence of mining two working faces on the dynamic pressure and large deformation roadway was studied by the FLAC3D numerical simulation method. On this basis, a new grouting material was developed, a complete set of technical schemes of full-section integrated cooperative support of dynamic pressure and large deformation roadways was proposed, and the field application effect was verified. The results showed that under natural geological conditions, the 2603 air inlet roadway was located within the influence range of the Wenwangshan South normal fault, which was significantly affected and controlled by the fault. The included angle between the roadway extension direction and the maximum principal stress was 74°, which was not conducive to the stability of the roadway. The range of the roadway loose zone was large. Under the existing support conditions, the surrounding rock could not form a relatively stable structure, which was one of the main reasons for the large deformation of the surrounding rock in the dynamic pressure roadway. The 2603 air inlet roadway was affected by the mining of both the adjacent working face and the 2603 working face. The stresses were superimposed, and the roadway was greatly deformed and damaged. A new grouting material was developed. A crosslinking agent prepared by toluene diisocyanate and polyether polyol was added to the existing polyurethane material to form a new grouting material, and a complete supporting technical scheme was proposed. The field application results showed that the displacement and floor heave of both sides of the roadway were reduced by approximately 87%, the deformation and failure of the coal and rock mass of the roadway were effectively controlled, and the deformation of the dynamic pressure roadway was greatly reduced.

Experimental Study on the Size of Rock Fragments Ejected from Boreholes Drilled in Coal Mine Roadway Floors

Borehole drilling is required if floor heave in underground mines is to be controlled using bolts through the floor. How well the bolt is anchored depends, in part, on the borehole’s quality. A major factor that can reduce borehole quality is the difficulty of discharging rock fragments from a small-diameter borehole drilled at a downward angle. Therefore, a fuller understanding of the sizes of the rock fragments will aid attempts to achieve smooth fragment discharge. In this study, drilling experiments in the laboratory and SEM imaging were carried out to determine the size and shape of the fragments generated when drilling boreholes in three sedimentary rocks typically found in roadway floors. The results show that the size distribution of the rock fragments conformed to the three-parameter generalized extreme value distribution. The mean fragment size increased with rock density and the mean size of the fragments larger than 1.5 mm increased with the rock’s uniaxial compressive strength. The fractal dimension of the cracks in the fragments was lower for high-density rocks and the mean fragment size was larger for rocks whose cracks had a lower fractal dimension. When a drill rod drills through very dense or high-strength rock, the mean size of the fragments will increase and the discharge power should be increased to prevent fragment discharge blockages. This paper may provide a theoretical basis and a data reference for discharge power settings and discharge channel optimization.

Novel high-performance automatic removal method of interference points for point cloud data in coal mine roadway environment

ABSTRACT In coal mine roadway, the reconstruction model obtained by 3D laser scanning is interfered by internal point cloud including dust, spray, auxiliary transportation vehicles, personnel flow, and so on, which seriously impacts deformation monitoring based on it. However, most of the current denoising methods barely consider the working conditions of roadway. Thus, this paper developed an automatic removal method of interference points with high efficiency and accuracy in coal mine roadway. It is realized through the establishment and transformation of local coordinate system, construction of voxel grid, bidirectional projection and central axis extraction, and noise removal based on a stepping bounding box. Under different levels of random noise and obstacle point clouds, the method has good performance. Based on the experimental results carried out in an underground roadway, the proposed approach takes 10 s to remove the interference points with an accuracy of 96%, which verifies the feasibility and effectiveness of the method.

Vision and Inertial Navigation Combined-Based Pose Measurement Method of Cantilever Roadheader

Pose measurement of coal mine excavation equipment is an important part of roadway excavation. However, in the underground mining roadway of coal mine, there are some influencing factors such as low illumination, high dust and interference from multiple equipment, which lead to the difficulty in the position and pose measurement of roadheader with low measurement accuracy and poor stability. A combination positioning method based on machine vision and optical fiber inertial navigation is proposed to realize the position and pose measurement of roadheader and improve the accuracy and stability of the position and pose measurement. The visual measurement model of arm roadheader is established, and the optical fiber inertial navigation technology and the spatial coordinate transformation method are used. Finally, the Kalman filter fusion algorithm is used to fuse the two kinds of data to get the accurate roadheader pose data, and the inertia is compensated and corrected. Underground coal mine experiments are designed to verify the performance of the proposed method. The results show that the positioning error of the roadheader body using this method is within 40 mm, which meets the positioning accuracy requirements of roadway construction. This method compensates for the shortcomings of low accuracy and poor reliability of single vision measurement, single inertial navigation measurement and single odometer measurement.

Construction and Application of On-Line Roof Separation Monitoring System Based on High-Precision FBG Indicator

Aiming at the existing problems of low efficiency, lagging monitoring results, and poor reliability and accuracy in the present roadway roof separation monitoring system, a high-precision Fiber Bragg Grating (FBG) separation indicator is designed through theoretical analysis, numerical simulation, and laboratory tests—according to the fiber grating sensing principle. Based on the Microsoft. Net platform, C# programming language, and VS2010 integrated development tools, the corresponding on-line monitoring software is developed. On this basis, a real-time on-line roof separation monitoring system is proposed. The high-precision FBG separator was calibrated and tested in the laboratory and results suggested that both the left and right arm demonstrate good sensitivity and linearity with linear fitting coefficient values of 0.9981 and 0.9979, respectively. The monitoring system was successfully applied to roof separation monitoring of the #14301 rail roadway in the Shaqu coal mine. The monitoring results showed that the on-line roof separation monitoring system based on the high-precision FBG separation indicator has the advantages of high precision, good stability, and long-distance signal transmission, which can achieve real-time dynamic monitoring and provides an effective method for long-term on-line monitoring of roadway roof separation.

Evaluation of Real-Time Perception of Deformation State of Host Rocks in Coal Mine Roadways in Dusty Environment

Intelligent mining needs to achieve real-time acquisition of surrounding rock deformation data of roadways and analysis and provide technical support for intelligent mining construction. To solve problems such as significant error, information lag, and low acquisition frequency of surrounding rock monitoring technology at the current stage, a perception method, RSBV of roadway deformation situation, based on binocular vision is proposed, which realizes the dynamic, accurate real-time acquisition of host rocks’ relative deformation in a dusky environment. The low illumination image enhancement method is used to preprocess original images, which reduces the impact of low illumination and high dust; the K-medoids algorithm segments the target image, and the SIFT algorithm extracts feature points from the ROI (region of interest). The influence of eliminating background images on the feature point extraction is revealed, and the efficiency of feature extraction is improved; the method of SIFT feature-matching with epipolar constraints is studied, which improves the accuracy and speed of feature points. The roadway deformation characteristics are analyzed, and the reflective target is used as the monitoring point. A roadway deformation acquisition and analysis platform based on binocular vision is built in a dim environment. Zhang’s method is selected to calibrate the camera parameters, and stereo rectification is carried out for the target motion image. The adaptability of the RSBV method to different surrounding rock deformation scales is studied and compared with the measurement results of the SGBM algorithm. The results show that the error of the RSBV method is controlled within 1.6%, which is 2.88% lower than the average error of the SGBM algorithm. The average time for processing a group of binocular images is 1.87 s, which is only 20% of the SGBM algorithm. The research result provides a reliable theoretical basis for the real-time and accurate evaluation of the surrounding rock deformation mechanism.

Development and application of a borehole stress meter in rocks surrounding the roadway, based on optical-fiber sensing technology

Stress in rock masses is an important parameter in the design and construction of underground engineering, such as the design and maintenance of mine roadways and the design of mining working faces. It is also a fundamental force causing the deformation and failure of geotechnical engineering excavation. At present, the abutment-pressure monitoring technology of the surrounding rocks of the coal mine roadway in China is not intelligent and systematic and lacks some high-precision sensing instruments and multi-functional monitoring systems. The mechanical model of the rocks surrounding the borehole was constructed by theoretical analysis of problems in the stress monitoring technology for underground rock masses in coal mines. Additionally, the interaction between the surrounding rocks and the borehole stress meter was analyzed. The borehole stress meters for tubular-structure fiber Bragg grating (TS-FBG) and cystic-structure fiber Bragg grating (CS-FBG) were designed by combining the sensing principle and sensing characteristics of fiber Bragg grating, and the performance of the two kinds of fiber Bragg grating borehole stress meters was compared by laboratory test. The track roadway of the 14,301 tested working faces in the Shaqu Coal Mine was taken as an example, and the stress of the rocks surrounding the 14,301-track roadway was monitored in real time by CS-FBG borehole stress meter during the mining of the working face. The following conclusions are drawn from the field application. The rig-site utilization results revealed obvious stress growth and stress peak zones in the mining-stress change curves of each measuring point on the two sides of the 14,301-track roadway in the process of mining the tested working face. Additionally, there were four stages: rapid rise, uniform growth, rapid rise to the peak, and rapid decline. Maximum stress monitored by the second station was 18.5 MPa, and the influence range of stress was over 140 m. Maximum stress monitored by the first measuring station was 19 MPa, the influence range of stress was about 80 m, and the peak stress position was about 20 m in front of the coal wall. Rig-site utilization proved the design of the CS-FBG borehole stress meter to be reasonable. Performance was stable and reliable, and the successful operation of field monitoring achieved the expected effect.

Study on Mechanical Properties of Ring Sandstone Specimen under Temperature and Water Coupling Dynamic Compression

The excavation of hard rock roadways in coal mines is often in the environment of underground water and high ground temperature, and it is easy to be affected by the dynamic load, which leads to roadway destruction and increases the difficulty of roadway support. The ring sandstone specimens with different inner diameters (0~25 mm) were treated with temperature and water coupled, and the dynamic compression test was produced by the Hopkinson pressure rod device (SHPB). The experimental results indicate that the coupling effect of temperature and water reduces the dynamic performance of sandstone specimens. XRD test results showed that the composition of sandstone specimens did not change before and after warm water coupling, and no new substances were found. Dynamic properties of ring sandstone specimens with different inner diameters weaken with the increase in inner diameters. With the increasing inner diameter of ring sandstone specimens, the energy dissipation per unit volume increases the dynamic compressive strength decreases, and the degree of breakage increases. Fracture morphology, average strain rate, and dynamic peak strain of ring sandstone specimens increase with inner diameter.

Mechanism and Application of Layered Grouting Reinforcement for Fractured Coal and Rock Roadway

This paper takes the ZF3806 working face of Shuiliandong Coal Mine in Binxian County, Shaanxi Province as the engineering background. Aiming at the problems of the development of surrounding rock cracks and roof breakage encountered in the process of roadway excavation and support and based on the composite beam theory, the method of layered grouting reinforcement of roadways is proposed according to the deformation and failure of the roadway roof and the internal drilling conditions. At the same time, combined with the splitting grouting mechanism, the roadway is strengthened and supported by layered grouting of “shallow bolt grouting + deep cable grouting”. The “shallow” and “deep” form a complete and stable composite beam support structure. After grouting, the bending moments of “shallow” and “deep” support beams decrease by 20.78 × 106 N·m and 26.50 × 106 N·m, respectively. The support scheme is applied to the field test, and the grouting effect is analyzed and monitored. The research results show the layered grouting support scheme of “shallow bolt grouting + deep cable grouting” can significantly improve the structural integrity of the roadway roof. The displacement of the two sides is within the controllable range, and the support role of the bolt and cable is entirely played through grouting. The roof displacement of the roadway is reduced by 65% on average, and the bolt failure and steel belt fracture are significantly reduced, which effectively controls the deformation and damage of the roadway and reduces the maintenance cost of the roadway while ensuring safe mining. The study’s findings could be useful in treating broken surrounding rock in other coal mine roadways.

Advanced detection for faults in front of coal mine roadways using seismic scattered waves

An unsuspected fault in front of a roadway is a key hidden disaster-causing factor that can result in major accidents in coal mines; therefore, the accurate advanced detection of faults is important for the safe coal mining. However, existing seismic advanced detection methods are difficult to execute because of the narrow space limits of roadways. Therefore, on the basis of the generalized theory of scattered waves and the scenes of advanced detections in roadways, we construct a new and superior advanced detection method using scattered waves. In this method, a virtual equivalent survey line perpendicular to the roadway strike is established to reconstruct scattered wave records and a polarization filter function is built to dynamically and accurately extract different types of scattered waves in the target area. An analysis of numerical simulations indicates the following. 1) The true reflection position of a fault in front of a rock roadway is closely related to its dip, and the proposed method can accurately extract and image the scattered multiwaves generated at the true reflection position to identify the inclination of the fault, which can avoid the arc-shaped illusion problem caused by the false reflection signal. 2) Under the condition that the scattered waves at the breakpoint of a broken coal seam are significantly disturbed by the coal seam waveguide effect, the fault inclination of the coal roadway can be determined by the joint imaging and interpretation on the reflected channel wave of the hanging wall breakpoint and the scattered wave of the footwall breakpoint. A field study was performed to verify the effectiveness of the proposed method. The results indicate that this method can effectively identify the position and inclination of faults and provide an effective new means for the accurate detection of faults in front of coal mine roadways.

Study on the Influence of Roadway Structural Morphology on the Mechanical Properties of Weakly Cemented Soft Rock Roadways

We used the 11,303 return air roadway of the Hongqingliang coal mine as the engineering background for a study exploring the impact of the structural morphology of the roadway on the stress distribution characteristics and the stability of a weakly cemented soft-rock mine roadway. This work studies the evolution law of stress and deformation, and the plastic zone of weakly cemented soft-rock roadways with retaining the top or bottom coal seams. The results show that when retaining the top coal is replaced by the bottom coal, the high-stress zone of the vertical stress is reduced, the peak stress is decreased, and the stress concentration coefficient is slightly reduced from 1.67 to 1.64. The peak value of the vertical displacement of the roof of the shaft which was 78.4% of that of the top coal also decreases significantly, while the peak value of the vertical displacement of the floor, which was 1.37 times that of the top coal, increases. The equal area method was used to change the aspect ratio of the roadway. When the aspect ratio decreased from 1.38 to 0.88, the high-stress zone of the vertical stress was reduced, the stress peak decreased, and the stress concentration coefficient decreased from 1.8 to 1.75. The vertical displacement of the roof increased by 27.7% from 10.91 mm to 13.93 mm, and the vertical displacement of the floor increased by 15.2% from 6.60 mm to 7.60 mm. The plastic failure range was significantly reduced, particularly at the bottom corners. These findings show that structural morphology has a great influence on the floor heave of weakly cemented soft rock. Reasonable retention of the top or bottom coal and the aspect ratio of the roadway can prevent the deformation and failure of the roadway in weakly cemented soft rock.

Deformation Characteristics and Control Mechanisms of Deep High‐Stress Large‐Span Roadways

Controlling the surrounding rock in soft rock roadways under deep high stress, strong rheology, and intensive mining is critical for the safety, efficiency, and economy of mine production. In this study, the mechanical properties, large deformation mechanism, and support countermeasures of surrounding rock in the high‐stress roadway in the Yuwu coal mine were systematically explored through laboratory tests, numerical calculations, and field measurements. It is shown that mudstone and sandstone are mainly composed of chlorite and kaolinite, respectively. Also, mudstone features elastoplasticity and experiences argillization and swelling in water. The mechanism of surrounding rock deformation in the high‐stress roadway in the Yuwu coal mine was determined. As the V‐shaped shear zone in the side corner expanded to the deep under high deviatoric stress, large‐scale tensile damage occurred in the shallow surrounding rock. Consequently, discontinuous stresses in deep and shallow parts induce the expansion and fracturing of the roadway. The deformation velocity and damage degree of surrounding rock rise exponentially under different stress release coefficients, so the reduced distance of the face roof under control and timely support is important for restricting the free surface. An idea of “timely and active reinforcing the side and strengthening the bottom” was proposed. This approach made the loads on all the support objects within the working range. The overall deformation of the surrounding rock was controlled within 350 mm, ensuring the long‐term stability of the roadway.

EXPERIMENTAL STUDY ON THE EVOLUTION OF MICROPORE STRUCTURE SOFTENED BY NONPRESSURE WATER ABSORPTION STRENGTH OF SANDSTONE

With the increase of mining depth of a coal mine, the strength of the surrounding rock in deep roadways decreases due to the influence of groundwater, which seriously affects the safety of on-site personnel in production. To study the influence of water-rock interaction on the properties of surrounding rock, taking the sandstone in the deep roadway of Wanfu Coal Mine as the research object. The nonpressure water absorption experiment was carried out. According to the compression tests of key water content (0%, 0.8%, 1.6%, 2.4%, 3.3%), the mechanical evolution law of sandstone during water absorption was studied. At the same time, mercury porosimetry (MIP), scanning electron microscopy (SEM), and nuclear magnetic resonance (NMR) experiments are used to study the evolution of experimental microscopic pores. The strength-softening mechanism of sandstone in Wanfu Coal Mine is discussed. The results show the following: (1) The NMR T<sub>2</sub> spectrum curve of sandstone presented a single peak characteristic. With the increase of water content, the total spectrum area increases continuously, and the corresponding relaxation time of peak shifts to the right. According to the ratio of spectral area in the experimental process, the traditional process of water absorption is further divided into four stages: rapid water absorption, uniform water absorption, pore transformation, and stable water absorption, in which the pore transformation mainly occurs in stage III (31-113 h). (2) The strength of sandstone decreases nonlinearly with the increase of water content, and the degree of attenuation is affected by confining pressure. The softening degree of strength decreases with the growth of confining pressure. With the rise in water content, both cohesion and internal friction angle show a negative exponential decreasing trend. (3) Expansion of clay minerals and the restraint of a quartz skeleton during the experiment are reasons for the closure of pores; misalignment of quartz particles, the flow of pore water, and dissolution of soluble minerals will lead to pore enlargement during water absorption. (4) In addition to the lubrication of water film and the decrease of the cementation ability of clay minerals, the expansion and connectivity of the pore are also important aspects of the softening of sandstone and influence the final destructive form of sandstone.

Curve forming prediction of coal mine roadway based on RBF interpolation.

Underground roadway excavation is a complex process, especially roadway curved excavation. In addition, the rationality of the design of coal mine roadway excavation scheme directly affects the speed of roadway excavation. The more reasonable the scheme design, the more conducive to rapid excavation. In order to avoid the influence of invalid construction on the efficiency of roadway excavation, this paper studies the forming of roadway bend. Based on the analysis of the tunneling process of the roadway curve, the mathematical model of the roadway curve is established. Taking the turning radius of the roadway curve as the evaluation index, the influence of various factors on the roadway curve excavation is analyzed. The research shows that the radius of the roadway curve increases with the increase of the feed rate, the working space position of the roadheader and the required width of the roadway, and decreases with the increase of the working space angle. Then, combined with the advantages of KNN algorithm, an interpolation model for calculating the radius of the curve is established based on RBF algorithm, and the radius of the tunnel curve is reconstructed and predicted. It provides a basis for the rational design of the construction process of the roadway bend and a reliable numerical algorithm for the design of the radius of the roadway bend. It also provides a theoretical basis for improving the efficiency of high roadway excavation in coal mines.

STUDY OF DEFORMATION PROPERTIES OF PROTECTIVE STRUCTURES OF PREPARATORY MINING WORKS

Purpose. To study the stability of the security structures of the preparatory mine roadways of steep seams while unloading the coal-rock massif to prevent the collapse of side rocks in the excavation areas of the coal mine and create safe working conditions for miners. Method. In order to achieve the aim of the research, the study of the stability of security structures was carried out at the laboratory of mountain pressure by using experimental samples in the form of whole coal and structures consisted of crushed rock, which were subjected to uniaxial compression. Results. Under the conditions of uniaxial compression of whole coal or constructions consisted of crushed rock, with the ratio of length to width a/b= (1-2) and an increase in the cross-sectional area S (m2) of the experimental samples, a relative change of their volume δV was observed. For whole coal, the steady state is ensured by the relative volume change δV ≤ 0,1. Beyond the set value of δV, the whole coals lose their stability and collapse, which results in the collapse of the side rocks. For the crushed rock structures, with an increase in the cross-sectional area of the compressible specimens, the relative volume change decreases from δV = 0,2 to δV = 0,35. At the same time, the crushed rock is compacted in the whole volume of the used material, the bearing capacity of protective structures is increased, which enables limiting the movement of lateral rocks and ensures their integrity. Scientific novelty Within the limits of the deformation resource of protective structures consisting of crushed rock of different granulometric composition, with their uniaxial compression, a type of functional dependence was established, which enables us to estimate the relative change in the volume of flexible supports from stiffness, which is necessary for assessing their bearing capacity. Practical significance. In order to create safe working conditions for miners in the excavation areas of a deep coal mine and prevent the collapse of side rocks in the coal massif, it is advisable to use flexible protective structures for the protection of preparatory coal mine roadways, when the ratio of their linear dimensions corresponds to the ratio of length to width of a/b>(1-2).

Design and Applicability of an Abandoned Coal Mine Roadway for Landfill Sites

Design and Applicability of an Abandoned Coal Mine Roadway for Landfill Sites