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Copyright of Coal Science & Technology (0253-2336) is the property of Coal Science & 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 situation of coal as the stabilizer guarantee the energy safety in China cannot be changed in the short term, and it will continue to face the problems of coal resource protection and the low utilization rate of coal-based solid waste. Through innovative mining methods, improving the recovery rate of coal resources and the large-scale disposal of coal-based solid waste, a new path is being paved for the green and sustainable development of the coal industry. Based on the in-depth research on the development status of coal mining technology, a new roadway excavation method of “excavation-backfill-retention” is proposed. This paper systematically discusses the scientific problems and key technologies of the “excavation-backfill-retention” construction method from three aspects: rapid excavation, continuous and efficient backfilling and safe construction of large-section roadways. The research results show that ① aiming at the engineering problems such as the fast excavation of large section roadway and the stability control of surrounding rock of heading face, three scientific problems are summarized: the matching mechanism between coal and rock characteristics and cutting parameters of roadway boring machine, the spatial transfer mechanism of overburden load and the deformation mechanism of surrounding rock, the interaction relationship between anchor/cable roof and support mechanism. The technology system has been built, which is based on the real-time sensing of the geological environment in the excavation area, the intelligent cooperative operation of the multi-process of falling, loading and transporting coal, the aging control of surrounding rock of the drilling anchor support together with excavation, the anti-leakage and ventilation optimization of the large section roadway. ② The scientific problems of continuous and efficient backfilling are summarized from the two aspects of timely construction of large section roadway bearing system and its bearing performance regulation, including the co-bearing mechanism of background coal anchor/cable, the hydration consolidation mechanism of multi-component solid waste base backfill materials, and the space-time evolution law of physical and mechanical characteristics of backfill are clarified. A continuous and efficient backfill key technology system with the core of safe and efficient backfill space construction, backfill material performance control and backfill material flow-consolidation perception has been established. The breakthrough of relevant theories and technologies can provide a theoretical basis for raw material selection and ratio design of backfill materials, additive development/selection and working performance control, excavation rate and backfill step optimization design, consolidation monitoring of backfill body, etc. ③ Based on the key problems of roadway safety and surrounding rock easy to break, sheet and damage in the whole life cycle, the paper elaborates three scientific problems: the spatial and temporal distribution characteristics of stress field of roadway surrounding rock, the evolution mechanism of roadway deformation and damage, the engineering quality monitoring and stability regulation theory of roadway surrounding rock. The key technology system is formed with the intelligent stability warning of the rock surrounding the roadway and the deformation control of the rock surrounding the roadway as the core. It is of great significance to conduct the scientific research and technical demonstration of the “excavation-backfill-retention” construction method in coal mines, and to realize the synergy of large-scale solid waste disposal, efficient coal pillar section recovery and rapid roadway excavation, which can promote the green and low-carbon transformation and development of the coal industry.

The overall strength of the surrounding rock of “three-soft” thick coal seam mining roadway is low, and the combination of rock structure generally changes greatly, resulting in obvious differences in the stability of hanging roof of driving face, and some areas with poor roof stability cannot directly adopt bolter miners and supporting construction technology, resulting in frequent stoppage of driving face and a decrease in the overall driving efficiency. In view of such problems, taking “three-soft” thick coal seam mining roadway of Shajihai Coal Mine as engineering background, and using comprehensive research methods such as on-site research, theoretical analysis and numerical simulation, it was clarified that roof leakage of driving face, bolter miner falling into the floor or mistracking, and rib spalling are the key constraints restricting the application of the bolter miner in “three-soft” thick coal seam roadway. Considering the influence of parameters such as the thickness of the hanging roof, the influence coefficient of disturbance, the strength of each rock layer of the roof and the integrity of each rock layer, the calculation formula of the limit span of hanging roof of driving face was established and derived. A stability grading method for surrounding rocks of roadway was formed dominated by the calculation of the limit span of hanging roof of driving face, and surrounding rocks of “three-soft” thick coal seam roadway is divided into 5 grades: extremely stable, stable, moderately stable, unstable and extremely unstable. Classification and optimization scheme of bolter miner equipment and construction process under different stability levels of surrounding rock is proposed, and the application countermeasures of bolter miner under difficult operating conditions are given from the aspects of cutting drum position adjustment, floor grounding treatment, and addition of roadway operation platform. The research results were applied in the roadway of Shajihai Coal Mine No.B1003W05 working face, and its classification optimization scheme can effectively ensure the normal operation of the bolter miner in “three-soft” thick coal seams, and the driving speed is increased by 1.0−1.8 times compared with fully-mechanized driving of boom-type roadheader.

The angle α between the fault strike and the axial direction of the roadway produces different damage characteristics. In this paper, the research methodology includes theoretical analyses, numerical simulations and field experiments in the context of the Daqiang coal mine located in Shenyang, China. The stability control countermeasure of "pre-splitting cutting roof + NPR anchor cable" (PSCR-NPR) is simultaneously proposed. According to the different deformation characteristics of the roadway, the faults are innovatively classified into three types, with α of type I being 0°–30°, α of type II being 30°–60°, and α of type III being 60°–90°. The full-cycle stress evolution paths during mining roadway traverses across different types of faults are investigated by numerical simulation. Different pinch angles α lead to high stress concentration areas at different locations in the surrounding rock. The non-uniform stress field formed in the shallow surrounding rock is an important reason for the instability of the roadway. The pre-cracked cut top shifted the high stress region to the deep rock mass and formed a low stress region in the shallow rock mass. The high prestressing NPR anchor cable transforms the non-uniform stress field of the shallow surrounding rock into a uniform stress field. PSCR-NPR is applied in the fault-through roadway of Daqiang mine. The low stress area of the surrounding rock was enlarged by 3–7 times, and the cumulative convergence was reduced by 45%–50%. It provides a reference for the stability control of the deep fault-through mining roadway. [ABSTRACT FROM AUTHOR]

The study focuses on the stability control measures for mining roadways in fault zones of deep mines, using Daqiang Coal Mine as a case study. The control system under consideration, referred to as "pre-splitting cutting roof + NPR anchor cable" (PSCR-NPR), is subjected to scrutiny through theoretical analysis, numerical modelling, and field trials. Furthermore, a comprehensive analysis is undertaken to evaluate the stability control mechanism of this particular technology. The study provides evidence that the utilization of deep-hole directional energy-concentrated blasting facilitates the attainment of directional roof cutting in roadways. The aforementioned procedure leads to the formation of a uniform structural surface on the roof of the roadway and causes modifications in the surrounding geological formation. The examination of the lateral abutment pressure and shear stress distribution, both prior to and subsequent to roof cutting, indicates that the implementation of pre-splitting techniques leads to a noteworthy reduction in pressure. The proposition of incorporating the safety factor Q for roof cutting height is suggested as a method to augment comprehension of the pressure relief phenomenon in the field of engineering. The analysis of numerical simulation has indicated that the optimal pressure relief effect of a mining roadway in a fault area is attained when the value of Q is 1.8. The NPR anchor cable exhibits noteworthy characteristics, including a high level of prestress, continuous resistance, and substantial deformation. After the excavation of the roadway, a notable reduction in radial stress occurs, leading to the reinstatement of the three-phase stress state in the surrounding rock. This restoration is attributed to the substantial prestress exerted on the radial stress. The termination point of the NPR anchor cable is strategically positioned within a stable rock formation, allowing for the utilization of the mechanical characteristics of the deep stable rock mass. This positioning serves to improve the load-bearing capacity of the surrounding rock. The mining roadway within the fault region of Daqiang Coal Mine is outfitted with the PSCR-NPR technology. The drop in shear stress experienced by the rock surrounding the roadway is estimated to be around 30%, whilst the low-stress region of the mining roadway extends by a factor of approximately 5.5. The magnitude of surface displacement convergence experiences a decrease of approximately 45%–50%. The study's findings provide useful insights regarding the stable of mining roadway in characterized by fault zones. [ABSTRACT FROM AUTHOR]

In geotechnical engineering projects, rock masses are subjected to various degrees of disturbance from geotectonic movements, rock drilling and mining before they are subjected to dynamic loads such as rock bursts, earthquakes, and blasting. We aim to investigate the dynamic mechanical properties, strain field, energy evolution, and progressive cracking of damaged sandstone under impact loading. In this study, sandstone specimens undergo various damage degrees caused by precompression and are characterized by computed tomography (CT) imaging. Then, the damaged specimens are subjected to impact tensile loads by employing a split Hopkinson pressure bar (SHPB) coupled with a high-speed camera and digital image correlation (DIC). The experimental results show that the energy dissipation density ratio, scale of the initial central crack, strain, and level of rock fragmentation in the vicinity of the bar-sample interfaces all increase with increasing driving pressure or sandstone damage degree. In contrast, the regular pattern of dynamic tensile strength is the opposite. We also find that the total strength rises before the prestress ratio of 0.2 and subsequently decreases as the sandstone’s damage degree increases. The rock’s dynamic tensile strength reduction ratio grows with the Weibull distribution as the damage degree expands. In addition, the function of the growth rate of the dissipated energy density ratio concerning the sandstone’s damage factor follows the Weibull distribution. These findings are of great significance to studying the mechanical responses of damaged rock and risk mitigation under dynamic catastrophes such as rock bursts, earthquakes, and blasting in rock engineering projects. [ABSTRACT FROM AUTHOR]

With the deepening of coal mining and the upsizing of mining equipment, the floor heave of the mining roadway has become an important problem that restricts the efficient and safe mining of the working face. It is of great significance to reveal the occurrence law of floor heave of the mining roadway for the stability control of the roadway floor. Based on the analysis of the deformation and failure characteristics of the mining roadway floor, com-bined with the key characteristics of the roadway floor heave, this paper studies the distributed optical fiber strain characterization method, and embeds the distributed sensing optical cable into the roadway floor through the borehole. Based on a large number of field measured data in the coal mine, the oc-currence of the roadway floor heave in the mining process of the working face is systematically analyzed. The results show that the distributed optical fiber has a positive strain peak and a negative strain peak respectively corresponding to the uncoordinated bending deformation characteristics of delamination and extrusion of the floor rock, and the local tension of the optical fiber corresponds to the crushing and extrusion expansion deformation characteristics of the floor rock. The strain value and strain growth rate of the optical fiber in the crushing characteristic area reflect the intensity of extrusion between the broken rock blocks. The evolution process of mining roadway floor heave is divided into three stages: disturbance, failure and relief uplift. The failure characteristics of floor strata in each stage are pointed out, and the key information of distributed optical fiber strain characteristic values in the crushing area in each stage is established. The conclusion of the study provides a new idea for the realization of large-scale distributed optical fiber monitoring of roadway surrounding rock, and has guiding significance for the floor heave control of mining roadway.

After coal mining enters the deep, the mining environment changes dramatically, and engineering disasters become increasingly prominent, which are mostly related to rock instability and failure. As traditional support is difficult to meet production needs, it is necessary to improve the support system. Based on the engineering background of the Pinggang mining roadway, this work studies the migration law of overlying strata in deep goaf by theoretical analysis and numerical simulation. The results show that the vertical stress and plastic failure range of the surrounding rock in front of the working face increase with the advance distance and when the working face advances to the first square, reaching the maximum. A stope spatial model considering the influence of horizontal stress is established. Combined with the theory of key strata, the stress transfer characteristics of overlying strata are analyzed. It can be seen that 0~30 m in front of the coal wall of the working face is the influence range of advanced abutment pressure, and the dynamic mining pressure in this range has a great influence. The inclined direction of the working face, 0~20 m away from the coal wall of the roadway, is the influence range of the solid coal abutment pressure. On this basis, the "migration- transfer- control" technical system of surrounding rock in deep stope face is put forward, i.e., the stress transfer of surrounding rock is caused by overlying rock migration, and the large deformation of surrounding rock is controlled by supporting means. Based on the original support scheme of the roadway, three reinforcement schemes are designed for the roof, the sidewalls, and both the roof and sides. The deformation control effect of the reinforcement scheme is far greater than that of the single factor, and the field monitoring effect is good. The research results aim to provide theoretical and technical support for the deformation control of mining roadways in the deep mining process. [ABSTRACT FROM AUTHOR]

Abstract The rockburst dynamic disasters in the process of deep coal mining become more and more serious. Taking the rockburst occurred in the 23130 working face of Yuejin Coal Mine as the engineering background, we study the characteristics of mining stress field around roadway, the plastic failure morphological characteristics of surrounding rock and the accumulation/release law of elastic energy before and after burst. An analysis model quantitatively describing the physical process of rockburst in the mining roadway is established, and the calculation method of dynamic release of elastic energy in the physical process of rockburst is educed. The mechanism of rockburst in mining roadway is revealed. The results show that an “L-shaped” stress concentration zone is formed within 100 m of the 23130 working face, and the principal stress ratio of the surrounding rock of the transportation roadway is 2.59–4.26. The change of the direction of the maximum principal stress has a significant effect on the burst appearance characteristics. The failure strength of different sections of the mining roadway is characterized by the elastic energy release value. With the increase of the working face distance, the elastic energy released by burst failure and the expansion variation of failure boundary radius show a nonlinear variation law that tends to decrease steadily after sharp fluctuation. The closer to the working face, the higher the burst risk. At a distance of 10 m from the working surface, the maximum principal stress reaches its maximum value. The butterfly-shaped failure system generated by the surrounding rock of the roadway has energy self-sustainability, and the elastic energy released by the sudden expansion of the butterfly leaf is enough to cause a burst damage of 1.9 magnitude. This work could provide theoretical support for the prediction and prevention of rockburst.

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. [ABSTRACT FROM AUTHOR]

Copyright of Coal Science & Technology (0253-2336) is the property of Coal Science & 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.)

In view of the serious deformation and failure of surrounding rock of high stress mining roadway near fault in the Shandong Xuchang Coal Mine, the support scheme and instability characteristics of the original mining roadway were analyzed by combining field measurement and numerical simulation. The asymmetric stability law of the mining roadway under the multiple superposition of fault structure, lateral abutment pressure of adjacent goaf and advanced abutment pressure of working face was studied. In this paper, according to the actual conditions of the 3318 working face belt transportation roadway in Xuchang Coal Mine, a new bolt-mesh support scheme with high strength, high stiffness and asymmetric characteristics is proposed. In this scheme, the 3318 working face belt transportation roadway is divided into two supporting sections A and B for layout. Through the field test, it is concluded that the deformation of surrounding rock of the 3318 working face belt conveyor roadway is reduced by more than 70 % after adopting the high strength and high stiffness asymmetric new anchor net support scheme. The relative displacement of roof and floor is reduced from 500 mm to 120 mm, and the relative displacement of two sides is reduced from 800 mm to 110 mm.

To solve these problems of poor supporting effect and serious deformation and failure of surrounding rock of mining roadway under deep mining stress, a FLAC-3D numerical calculation model is established with −800 m level no. 2424 upper roadway in the Suncun Coal Mine as the background to compare the stress, deformation, and failure law of surrounding rock of mining roadway under once support and multi-level support with the same support strength. It is found that the multi-level support technology has obvious advantages in the surrounding rock of the horizontal roadway on the 2424 working face. From this, the key parameters of multi-level support are determined, and the field industrial test is carried out. The results show that the overall deformation of the surrounding rock is obviously reduced after multi-level support. The displacement of the two sides is reduced by about 40%, the displacement of the roof and floor is reduced by about 30%, and the plastic zone of the roadway is reduced by about 75%. The peak value of concentrated stress decreases from 98.7 MPa to 95.8 MPa, which decreases slightly. The integrity and stability of the surrounding rock are excellent, and the support effect is satisfactory. The research can provide reference and technical support for surrounding rock control of deep high-stress mining roadways. [ABSTRACT FROM AUTHOR]

In view of the problems of roof collapse and difficult roof support in composite roof roadway, the deformation and instability mechanism of composite roof is analyzed, and the cooperative support technology of long and short anchor cables is proposed. The control effect of the original roadway support mode and the high-strength pre-stressed long and short anchor cable cooperative support mode on the roadway surrounding rock is analyzed by numerical simulation. The results show that the improved long and short anchor cable cooperative support scheme can effectively control the roadway deformation and failure, and the volume of roadway plastic zone is reduced by 29.1%; the field monitoring data show that the roof and floor displacement, two side displacement and roof subsidence of the roadway are reduced by 63.6%, 60.4% and 60.2% after the cooperative support of long and short anchor cables, indicating that the support method has a good control effect on the surrounding rock of the roadway with composite roof.

• Analyzed the main fracture positions and types of on-site bolts. • Established a comprehensive criterion for bolt fracture considering multiple loads. • Proposed the best reinforcement support technology scheme for bolt breakage. To reveal the problem of local instability caused by bolt breakage and failure in deep mining roadway under impact dynamic loads, and explore strengthening support technologies that can reduce bolt breakage and improve the stability of roadway support bodies. This article adopts theoretical analysis, numerical simulation, and on-site industrial experiments to conduct research, investigate and obtain the fracture failure characteristics of bolt in deep mining roadway, quantitatively characterize the deformation pressure of roadway surrounding rock and dynamic load of overburden fracture, establish the mechanical criterion of bolt fracture, and analyze the influence law of different anchoring factors on bolt force under static load and dynamic and static load combination. The results show that when the anchor angle is different, the range under dynamic load increases by 169.3 % compared with static load, when the anchor length is different, the range increases by 863.3 % relatively, and the influence is significant; while the anchor support resistance increases by 11.6 % at different times, and the range decreases by 41.5 % at different pre-tightening torque. Then, based on this criterion, the influence law of bolt failure on the stability of surrounding rock is analyzed, and the optimal support scheme is obtained by simulation research, that is, bolt cable +U steel support scheme. After adopting this scheme for support, the deformation of surrounding rock is reduced by about 60 %, and the maximum concentrated stress of surrounding rock of roadway is reduced by 15.0 %. Based on this, the support parameters of the on-site roadway were optimized and a strengthening support scheme was determined, which includes "roof bolt surface support reinforcement + anchor cable combined with U-shaped steel deep reinforcement, and two strong bolts advanced reinforcement". The on-site strengthening support practice showed that the bolt fracture rate was reduced by 87.3 %, the deformation of the surrounding rock was effectively controlled, and the stability was significantly improved. [ABSTRACT FROM AUTHOR]

The rockburst dynamic disasters in the process of deep coal mining become more and more serious. Taking the rockburst occurred in the 23130 working face of Yuejin Coal Mine as the engineering background, we study the characteristics of mining stress field around roadway, the plastic failure morphological characteristics of surrounding rock and the accumulation/release law of elastic energy before and after burst. An analysis model quantitatively describing the physical process of rockburst in the mining roadway is established, and the calculation method of dynamic release of elastic energy in the physical process of rockburst is educed. The mechanism of rockburst in mining roadway is revealed. The results show that an "L-shaped" stress concentration zone is formed within 100 m of the 23130 working face, and the principal stress ratio of the surrounding rock of the transportation roadway is 2.59–4.26. The change of the direction of the maximum principal stress has a significant effect on the burst appearance characteristics. The failure strength of different sections of the mining roadway is characterized by the elastic energy release value. With the increase of the working face distance, the elastic energy released by burst failure and the expansion variation of failure boundary radius show a nonlinear variation law that tends to decrease steadily after sharp fluctuation. The closer to the working face, the higher the burst risk. At a distance of 10 m from the working surface, the maximum principal stress reaches its maximum value. The butterfly-shaped failure system generated by the surrounding rock of the roadway has energy self-sustainability, and the elastic energy released by the sudden expansion of the butterfly leaf is enough to cause a burst damage of 1.9 magnitude. This work could provide theoretical support for the prediction and prevention of rockburst. [ABSTRACT FROM AUTHOR]

In a roadway affected by the superposition of in situ stress and mining-induced stress, inhomogeneous deformation and even roof accidents may occur. The stability control of rock surrounding a mining roadway is the key to realizing safe and efficient mining. A track roadway of the No. 152106 working face in Changling No. 1 Coal Mine was severely deformed under the influence of mining. In view of this, deformation characteristics of rock surrounding a plastic zone in the mining roadway were investigated by field monitoring, theoretical analysis, and numerical simulation. The results demonstrate that deformation of rock surrounding the roadway is inhomogeneous under the influence of mining. The deformation of rock surrounding the roadway in rear of the working face is greater than that in front of the working face and deformation of a coal pillar in the roadway is larger than that of solid coal. Furthermore, bed separation occurs on the roof and the floor heave near the coal pillar is greater. The maximum principal stress, ratio of the maximum principal stress to the minimum principal stress (hereinafter referred to as principal stress ratio), and range of the plastic zone in front of the working face are smaller than those to rear of the working face, and the displacement and range of the plastic zone in rock surrounding the roadway are consistent in terms of trend. Affected by secondary mining, the plastic zone changes from an elliptical to a butterfly shape. On this basis, reinforcement support schemes for the mining roadway were proposed, namely adding anchor cables to the roof, applying thru-anchor cables to coal pillars, and setting single hydraulic props in a roadway affected by primary mining. The field test results show that deformation of rock surrounding the track roadway decreases significantly. [ABSTRACT FROM AUTHOR]

Aiming at the surrounding rock failure of heterogeneous and unequal pressure circular roadways, the approximate analytical algorithm of the plastic zone is proposed. Through the comparison of analytical calculations and numerical simulation, the shape characteristics and evolution law of the surrounding rock's plastic zone are studied, and the relative error of the two calculation methods is analyzed. The results show the following: (1) With an increase or decrease in the lateral pressure coefficient, the shape of the plastic zone of the roadway-surrounding rock presents a circular-ellipse-butterfly shape change law, and the outer edge of the plastic zone presents a scattered shape, without a continuous boundary. (2) In the butterfly-shaped plastic zone, the butterfly leaf always lies between the maximum confining pressure and the minimum confining pressure and rotates with the pressure. (3) There is a certain amount of error between the maximum value of the plastic zone solved by an analytical algorithm and numerical simulation, and the relative error is positively related to the burial depth and lateral pressure coefficient of the roadway and negatively related to the strength of the surrounding rock. (4) In addition, the relative error of the plastic zone calculation of the multi-layer heterogeneous combination roadway is larger than that of the single heterogeneous roadway. [ABSTRACT FROM AUTHOR]

Copyright of Coal Science & Technology (0253-2336) is the property of Coal Science & 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 Coal Science & Technology (0253-2336) is the property of Coal Science & 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.)

After coal mining enters the deep, the mining environment changes dramatically, and engineering disasters become increasingly prominent, which are mostly related to rock instability and failure. As traditional support is difficult to meet production needs, it is necessary to improve the support system. Based on the engineering background of the Pinggang mining roadway, this work studies the migration law of overlying strata in deep goaf by theoretical analysis and numerical simulation. The results show that the vertical stress and plastic failure range of the surrounding rock in front of the working face increase with the advance distance and when the working face advances to the first square, reaching the maximum. A stope spatial model considering the influence of horizontal stress is established. Combined with the theory of key strata, the stress transfer characteristics of overlying strata are analyzed. It can be seen that 0~30 m in front of the coal wall of the working face is the influence range of advanced abutment pressure, and the dynamic mining pressure in this range has a great influence. The inclined direction of the working face, 0~20 m away from the coal wall of the roadway, is the influence range of the solid coal abutment pressure. On this basis, the “migration- transfer- control” technical system of surrounding rock in deep stope face is put forward, i.e., the stress transfer of surrounding rock is caused by overlying rock migration, and the large deformation of surrounding rock is controlled by supporting means. Based on the original support scheme of the roadway, three reinforcement schemes are designed for the roof, the sidewalls, and both the roof and sides. The deformation control effect of the reinforcement scheme is far greater than that of the single factor, and the field monitoring effect is good. The research results aim to provide theoretical and technical support for the deformation control of mining roadways in the deep mining process.

Aiming at the situation that the top coal of the close distance coal seams is goaf and the remaining 30 m coal pillar, taking the 2-1 coal seam and 2-2 coal seam of Hulusu Coal Mine as the research background, the mechanical model of the upper coal goaf and the remaining coal pillar under force is established, the stress distribution state of the strata under the coal pillar in the upper coal section is analyzed, and the reasonable spacing of the stoping roadway under the close distance coal seams goaf is studied. The research shows that the optimal offset distance should be 80 m after the protective layer is fully discharged; from the influence range of the overlying coal pillar, the optimal offset distance is 40-80 m; considering the degree of influence on the upper coal roadway, the optimal offset distance should be greater than 80 m; when the offset distance is 160 m, the lower working face mining has the lowest influence on 21101 return air alley. By combining 4 different angles and calculating the intersection of the influence range, the optimal offset distance of the first working face of 22103 was finally determined to be 80 m.

In view of the large deformations and difficult support problems in the mining roadway of the No. 5313 mining face in Sanhui No. 3 Mine, the mechanical properties of the surrounding rock were determined via laboratory experiments and the reason of floor heave was determined to be the flow of rock mass caused by compression. To reveal the deformation mechanism of the roadway, the mechanical model was established via numerical simulation to analyze the deformation, stress distribution, and plastic zone distribution of the surrounding rock when the roadway was unsupported and under original support. The results showed that the roadway is affected mainly by tensile and shear failure. Relatively, the roof of the roadway had been effectively supported and the subsidence was not large, while the damage on the two walls and the floor were serious. Through numerical calculation and theoretical analysis, the final roadway support method was determined to be "self-drilling grouting anchor bolt + high-strength rebar anchor bolt + 'W' type steel belt + steel mesh + anchor cable with bird cage." Through field test, the deformation of two walls can be controlled at about 100 mm, and the floor heave at 90 mm. The support scheme can effectively control the deformation of the roadway and ensure the safety. It can be concluded that the support for soft rock roadway should cover the whole section, not just the roof and two walls. Especially for the roadway with soft rock floor, floor bolt support is essential. Moreover, in the soft rock roadway, high strength support materials should also be recommended. [ABSTRACT FROM AUTHOR]

Aiming at the deformation and failure of roadway surrounding rock and its control problems under goaf in upper and lower coal seam mining of Buertai Coal Mine, the distribution characteristics of surrounding rock stress in different mining stages of goaf were analyzed, the evolution law of plastic zone of roadway surrounding rock under goaf was analyzed, and the failure mechanism of roadway surrounding rock was revealed by theoretical calculation and numerical simulation.The results show that: the principal stress of the mining roadway under the goaf is smaller than that of the original rock stress. The plastic zone of surrounding rock is small during excavation. Affected by the first mining, the maximum principal stress is 1.24 times of the original rock stress, and the minimum principal stress is 1.49 times of the original rock stress. Affected by the secondary mining, the maximum principal stress is 1.52 times of the original rock stress, and the minimum principal stress is 1.74 times of the original rock stress. In order to control the malignant development of surrounding rock plastic zone, the staged support technology in different mining stages is proposed, and the stress environment of surrounding rock is improved by hydraulic fracturing, so as to reduce the plastic zone of surrounding rock and maintain the safety and stability of surrounding rock. [ABSTRACT FROM AUTHOR]

Aiming at the problems of roadway deformation and support difficulty under the influence of lateral mining, taking 22304 return air roadway of Bulianta Coal Mine as the research background, through theoretical analysis and numerical simulation method, the distribution law of surrounding rock stress is obtained, and the relationship among different positions of surrounding rock, main stress difference and plastic area is analyzed from multi-dimensional perspective, and the failure mechanism of surrounding rock is obtained, and the control effect of surrounding rock reinforcement is further analyzed. The results show that the stress distribution of the surrounding rock in the side entry of the goaf shows a certain regularity in space, the main stress changes a lot in the rear of the working face, and the main stress difference is stable about 300 m behind the coal wall; the main stress difference has a positive correlation with the size of the plastic area; the main stress size and direction change of the surrounding rock behind the working face lead to the asymmetric distribution characteristics of the plastic area; then, the key parts of the reinforcement support are determined. Through analysis, the reinforcement scheme is highly targeted and can achieve the purpose of synergistic control of the two sides and the roof to ensure the stability of surrounding rocks.

The overlying strata of the Yima coalfield are ultrathick conglomerate. Aiming at the problem of frequent occurrence of rockburst events in the central Yima coalfield during 2006–2015, the characteristics of rockburst events, microseismic (MS) monitoring, and rockburst event-inducing factors were analyzed through data mining and field investigation methods. The results showed that the rockburst events in roadways mainly occurred during mining of the working face, and they occurred at a large buried depth and were within the influence of mining stress, accompanied by an abrupt energy release. The occurrence of rockburst in roadways was accompanied by a sudden release of energy. The ultrathick strata and the fault nearby were the key influence factors of rockburst events. The stress field of roadway surrounding rocks was changed because of the mining disturbance, roadway repair and maintenance, and blasting, which would change the regional stress fields in the surrounding rocks and induce roadway rockburst events. The characteristics of rockburst events were floor heave, sharp convergence of two side walls, severe damage of the supporting body, and even closure of the roadway. The occurrence of rockburst can be prevented by reducing the mining speed and injecting water into coal seam.

To solve these problems of poor supporting effect and serious deformation and failure of surrounding rock of mining roadway under deep mining stress, a FLAC-3D numerical calculation model is established with −800 m level no. 2424 upper roadway in the Suncun Coal Mine as the background to compare the stress, deformation, and failure law of surrounding rock of mining roadway under once support and multi-level support with the same support strength. It is found that the multi-level support technology has obvious advantages in the surrounding rock of the horizontal roadway on the 2424 working face. From this, the key parameters of multi-level support are determined, and the field industrial test is carried out. The results show that the overall deformation of the surrounding rock is obviously reduced after multi-level support. The displacement of the two sides is reduced by about 40%, the displacement of the roof and floor is reduced by about 30%, and the plastic zone of the roadway is reduced by about 75%. The peak value of concentrated stress decreases from 98.7 MPa to 95.8 MPa, which decreases slightly. The integrity and stability of the surrounding rock are excellent, and the support effect is satisfactory. The research can provide reference and technical support for surrounding rock control of deep high-stress mining roadways.

A study of the deformation of the surrounding rock and coal pillars near a fault under the influence of mining is conducted on a physical model for the design of coal pillars to support and maintain the roofs of adjacent fault roadways. This research is based on the 15101 mining face in the Baiyangling Coal Mine, Shanxi, China, and uses simulation tests similar to digital speckle test technology to analyse the displacement, strain and vertical stress fields of surrounding rocks near faults to determine the influence of the coal pillar width. The results are as follows. The surrounding rock of the roadway roof fails to form a balance hinge for the massive rock mass. The vertical displacement, vertical strain and other deformation of the surrounding rock near the fault increase steeply as the coal pillar width decreases. The steep increase in deformation corresponds to a coal pillar width of 10 m. When the coal pillar width is 7.5 m, the pressure on the surrounding rock near the footwall of the fault suddenly increases, while the pressure on the hanging wall near the fault increases by only 0.35 MPa. The stress of the rock mass of the hanging wall is not completely shielded by the fault, and part of the load disturbance is still transmitted to the hanging wall via friction. The width of the fault coal pillars at the 15101 working face is determined to be 7.5 m, and the monitoring data verify the rationality of the fault coal pillars. [ABSTRACT FROM AUTHOR]

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Copyright of Journal of Heilongjiang University of Science & Technology is the property of Journal of Heilongjiang University of Science & Technology Editorial Department 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 stability control of mining roadways is crucial in ensuring the safe and efficient mining of deep coal resources. Given the effect of mining stress on the working face, the support scheme of such roadways, which is designed based on the original in-situ stress parameters, often presents support-related problems. A mining roadway on the 1131 working face of Zhujidong Coal Mine in the Huainan mining area, China was taken as the engineering background of this study. To explore the influence of mining stress on the stability control of this roadway, the 2-dimensional (2D) Particle Flow Code (PFC) numerical simulation software was used to perform a simulation study on the stress distribution characteristics and deformation failure laws of the surrounding rocks under the change in the roadway lateral pressure coefficient caused by the mining stress. An improved support scheme that considers the influence of varying lateral pressure coefficient on the mining roadway was then proposed. Results show that when the lateral pressure coefficient increased from 1 to 1.4, the maximum principal stress (61.2 MPa) is observed at 2.9 m inside the roof of the surrounding rocks in the roadway. When the lateral pressure coefficient decreases from 1 to 0.4, the maximum principal stress (46.2 MPa) is observed at 2.2 m inside the surrounding rock of sidewalls of the roadway, and failure occurs. These findings suggest that the deformation and failure of surrounding rocks are affected regardless of the lateral pressure coefficient increase or decrease. On this basis, the lengths of the anchor bolts in the roof and sidewalls in the original support method are increased from 2,200 mm to 3,000 mm and 2,500 mm, respectively. The field monitoring results indicate that the improved support method mitigates the deformation and realizes the stability control of the roadway surrounding rocks. The findings of this study could provide a scientific basis for the parameter design of roadway support. [ABSTRACT FROM AUTHOR]

Aimed at the large amount of mining roadway roof subsidence in argillaceous rock, as well as frequently happened roof caving accidents, the mining roadway from Baode coal mine was taken as the research background. By the integrated use of field measurement, numerical simulation, and the theoretical analysis, the deformationfailure characteristics and engineering controllability of mining roadway roof in argillaceous rock was studied. The results indicate that: During the mining influence. This kind of roadway suffers serious roof deformation and failure and has little to do with the increase of the support strength. The roof subsidence is far out of the endurance of the anchor cable. The roof breakage depth is around 4.0m. With the existing technology, it is not available to limit the roof subsidence by high-strength bolting, and it is a must to adopt the supporting method with good extension property, which gives priority to roof caving control. Accordingly, the control strategy which gives priority to long-extension bolt appeared. The engineering testing results indicate that this technology can coordinate with the roof deformation, thus effectively prevent the roof caving. [ABSTRACT FROM AUTHOR]

On the background of one deep thick seam coal mine using fully-mechanized caving mining in Datong Coal Mine Group Co., Ltd., surrounding rock instability regularity and support scheme of deep mining roadway affected by dynamic pressure were studied with methods of surrounding rock geomechanics test, coal pillar stress measurement and reasonable coal pillar size determination. The study results show that mean compressive strength of roof coal, gritstone and No.4 coal seam is 32.08, 89.85 and 17.61 MPa individually. The maximum horizontal principal stress, the minimum horizontal principal stress and vertical stress of the measured area is 26.26, 13.39 and 15.80 MPa individually, direction of the maximum horizontal principal stress is N34.4°W, and in-situ stress filed belongs to high stress area on numerical value. During period of the first dynamic pressure, influence range and degree on coal pillar of advanced support pressure are far less than the ones of mining-induced stress after working face stoping ahead. During period of the second dynamic pressure, coal pillar located in 8-18 m borehole depth is in elastic kernel area, and reasonable coal pillar width is no less than 55 m. The initial support design of 14103 working face auxiliary transport roadway was proposed. The results of industrial field tests show that effective cross section area is 97.5% as large as excavation cross section after 14102 working face stoping ahead. During stoping 14103 working face, convergence between roof and floor in auxiliary transport roadway is about 300 mm, and convergence between two sides is about 260 mm, which can completely realize mine safety production.

Copyright of Journal of Heilongjiang University of Science & Technology is the property of Journal of Heilongjiang University of Science & Technology Editorial Department 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.)

By analyzing and studying the deduced theory of the surrounding plastic zone in the circular mining roadway, it is found that the radius of the surrounding plastic zone in the roadway considering the influence of mining coefficient can be divided into two stages: In the first stage, when the mining coefficient is small, the radius of the plastic zone is less sensitive to the mining coefficient, and the process increases linearly with the gradual increase of the mining coefficient. In the second stage, when the mining coefficient increases to a certain extent, the sensitivity of the radius of the plastic zone to the mining coefficient increases rapidly, and the non-linearity increases rapidly with the increase of the mining coefficient. With the gradual increase of the mining coefficient, the geometrical distribution morphology of the surrounding plastic zone of the roadway varies from circular to ellipse to round rectangle to butterfly, and the larger the mining coefficient, the more easily the surrounding rock is butterfly plastic zone, and the developmental dimension and range of the butterfly-leaf are larger. The growth of the buried depth of the roadway and the decrease of the cohesion and internal friction angle of the surrounding rock will lead to an increase in the radius of the plastic zone. With the rise of the mining coefficient, the sensitivity of the plastic zone radius to the buried depth of the roadway, cohesion and internal friction angle gradually enhanced. The butterfly plastic zone of the mining roadway has directional, and the butterfly-leaf will rotate to different degrees with the change of the principal stress direction of the surrounding rock of the roadway, When the maximum depth of butterfly-leaf plastic zone is located directly above the roof of roadway, the roof stability is the worst, and roof caving is easy to occur, thus, the support should be strengthened. [ABSTRACT FROM AUTHOR]

Under the superposed action of the primary rock stress and the mining stress, the compound roof of a roadway will have irregular plastic failure zone with greater depth, resulting in a wide range of non-uniform deformations and roof failures. Mastering the deformation and failure characteristics of this roof is essentially to recognize the development of the plastic zone of a compound roof. In this paper, the on-site roof detection method is mainly adopted to arrange a large number of boreholes for visualization and the deep displacement monitoring with the high-density points. Combined with numerical simulations, the rupture development characteristics and deformation mechanisms of the compound roof are revealed. The results show that the magnitude and direction of the principal stress of surrounding rock in a mining roadway are constantly changing, and the penetrating phenomenon will occur during the plastic zone expansion process. The order of the compound roof rupture as follows: shallow strata plastic failure, deep strata penetrating plastic failure and middle strata rupture. Severe roof deformation is mainly caused by plastic failure, and the strong deformation pressure caused by deep strata penetration plastic failure can easily lead to tensile failure and rupture in the middle strata. According to the plastic zone penetration development of the compound roof, the hierarchical support design led by the long-extension bolt is carried out on the test roadway. The monitoring results show that the roof is controlled well. The research results can provide a reference for the control of compound roofs in mining roadways.

In view of the problems such as the shortage of filling time and filling space,the difficulty of coordination between coal mining and filling operation and so on,the new method named “backfilling while mining” was applied to water-preserved mining.In the mining of process,all the roadway in the mining block is divided into several mining stages.The work on the roadway's mining and filling in the next stage begin when the previous stage’s work are finished.With the work on all the roadway's mining and filling finished,the filling body will substitute coal absolutely.For the purpose of the roadway's sides being solid coal or filling body reaching the designed strength,the roadway should be excavated alternately.The research results are applied to Wangtaipu coal mine.Field practice shows that under the condition of the mining rate of the whole block reaching 96.8%,and the surface deformation is less than the Grade I damage index,the shallow water resources will be preserved effectively.The method applies the mining pattern of “backfilling while mining” so it can realize the advantage of fast continuous mining and backfilling mining and achieve the work on water-preserved mining. [ABSTRACT FROM AUTHOR]

This study considered the mining roadway with coal pillar protection in the fully mechanized caving face of the Dananhu No.1 Coal Mine, China. Theoretical analysis, numerical simulation, and field tests were conducted, and the stress environment, deformation, and failure characteristics of the mining roadway in the fully mechanized caving face were analyzed. The results revealed that the intrinsic cause for the large asymmetrical floor deformation in the mining roadway is the asymmetrical phenomenon of the surrounding rock’s stress environment, caused by mining. This also results in the non-uniform distribution of the mining roadway floor’s plastic zone. The degree of asymmetrical floor heave is internally related to the thickness of the caving coal. When the thickness of the caving coal was in the range of 5.9 m, the deformation of the asymmetrical floor heave, caused by the plastic failure in the floor, became more obvious as certain parameters increased. As the rotation angle of the principal stress direction increased, the maximum plastic failure depth position of the floor gradually moved toward the middle of the roadway. This caused a different distribution for the maximum deformation position. The control of the floor heave deformation was poor, and it was not feasible to use high-strength support under the existing engineering conditions. Hence, the control should mainly be applied to the floor heave deformation. When the thickness of the caving coal was more than 5.9 m, the main roof strata was prone to instability and being cut along the edge of the coal pillar; the rock stress environment surrounding the roadway tended to revert back to the initial geostress state. The proposed floor heave control strategy achieved good results, and as the deformation of the floor heave decreased, the workload of the floor heave was also greatly reduced.

In order to further investigate the occurrence mechanism of blast disaster in coal mine，the influence of working face extraction on the regional stress field of surrounding rock at the haulage gateway of 13230 working face is analyzed by way of numerical simulation based on “12·22” rock burst accident of Gengcun Coal Mine，and the curves of principal stress are obtained along the axial direction of mining roadway.Due to the induction of external disturbances such as coal cutting，caving，first or periodic weighting of working face，front or side abutment pressure and so on，the biggest size of plastic zone is expanded by 2.2-3.4 times.Therefore，the occurrence mechanism of “12·22” blast disaster in Gengcun Coal Mine is revealed.In the geological environment，because of the induction of triggering event like external disturbances，the regional stress field of surrounding rock at the haulage gateway of 13230 working face will be suddenly changed，and a huge amount of elastic energy which is gathered in the body of coal will be suddenly released in the form of vibration，sound and coal or rock [ABSTRACT FROM AUTHOR]

The fracture and movement of hard thick strata, particularly super thick hard key stratum, can induce strong mine seismicity. The disturbance caused by mine seismicity can directly influence the stability of a roadway. To address this problem, the numerical simulation software FLAC2D was used to simulate strong seismicity by applying strong stress waves on the bottom of hard thick strata. The stress, displacement, and plastic zone data of roadway surrounding rock were extracted. The dynamic response laws of roadway surrounding rock under the disturbance were investigated. The influence of boundary condition on the dynamic response of the roadway was studied simultaneously. Result indicates that the increase in horizontal stress of the roof and vertical stress of the ribs result in the spallation damage of the roof and the compression of the coal ribs under seismic influence. The convergence of the ribs is greater than that of the roof and the floor, and rock bursts can easily occur in the ribs of the roadway. The significant influencing time for the ground displacement of the roadway is 0.6 s. The convergence of two ribs of the gob-side roadway is 9.27 times as high as that of the solid-coal roadway. The results are verified via a case study. The conclusions obtained in this study provide a theoretical basis for the design of a roadway support on hard thick rock strata, which is significant to the safety of the working face. [ABSTRACT FROM AUTHOR]

Roof caving accidents of mine roadway in deep mining is a major problem faced with the exploitation of coal resources. Based on the stress environment of the mine roadway surrounding rock in deepmining, the formative mechanics and morphological characteristics of the plastic zone of surrounding rock on bidirectional non-constant pressure were analyzed, and the factors affecting the stability of the mine roadway roof in deep mining were discussed. The results indicate that: ① When the two-way pressure ratio λ(0<λ<1) of the surrounding rock of mine roadway is less, the morphology of the plastic zone of roadway surrounding rock is no longer circular or ovaland shows the characteristics of butterfly distribution; when the butterfly leaf is above the roadway roof, the roof caving is easy to occur; ② The location of the maximum damage depth is determined by the direction of mining-induced stress, which also determines the height and the range of potential caving zone; when the maximum damage depth of the surrounding rock is equal to the potential caving height, the roof is most unstable. To ensure the roof stability, the support must have enough length and extension performance, accordingly, the long-extension bolt support technology is put forward; the field tests indicate that: the long-extension bolt adapts to the intense subsidence of roof surrounding rock, and better supporting results are obtained. [ABSTRACT FROM AUTHOR]

An intelligent transportation system is an important part of the smart city. The roof control of (MR) in safe and efficient mining of coal mine is analyzed and studied to solve the obstacles to the development of wireless intelligent sensors in the intelligent transportation system. The idea of controlling roadway deformation by using the deformation and development of plastic zone has been innovatively put forward. Based on the butterfly-shaped plastic zone theory of surrounding rock of MR and the countermeasures of asymmetric roof support, Fast Lagrangian Analysis of Continua (FLAC3D) software is used to construct the numerical model of uneven deformation and failure of roof, and the uneven failure of surrounding rock of MR in Lijiatun Coal Mine is analyzed. The uneven distribution characteristics of MR under dynamic influence conditions show that after the mining effect, the roadway surrounding rock will produce large deviatoric stress, and the direction of the maximum principal stress will tilt to one side of the working face, to maximize the plasticity of one side of the roadway roof. Especially after secondary mining, the maximum position of plastic failure on the side of the roadway roof is more obvious, accompanied by the uneven failure of the roof. On this basis, the asymmetric support strategy of the roadway roof is proposed to strengthen the roof on the side with serious deformation. The maximum uneven expansion of the plastic zone after reinforcement occurs in the 11,209 working face 200m, not more than 45mm. This reinforcement scheme reduces the uneven deformation of the roof. The new technology clears the obstacles for the development of wireless intelligent sensors and lays a good foundation for the rapid development of smart cities. [ABSTRACT FROM AUTHOR]

In order to study the mechanism and effective countermeasures of floor heave in large section mining roadway, one of its prediction methods was put forward through theoretical deduction. It is showed that floor rock beam with lower critical stress is easier to instability, along with larger section of mining roadway. Almost all large section roadway are subject to the threat of floor heave under horizontal force. Moreover, with the increasing width of tunnel, the heave volume increases approximately linearly. At the same time, three kinds of support scheme, roadway support, reinforcement of sides, comers and roof, were analysed with Ansys. A conclusion is drawn that floor heave can be controlled well by installing roof bolting based on floor on a small scale with the reinforcement of working slope, angle and roof. [ABSTRACT FROM AUTHOR]