In order to explore the mining pressure development rule of gob-side entry retaining during deep thin coal seam mining, FLAC3D numerical simulation is applied to analyze the stress distribution rule of gob-side entry retaining, observing the left third working face of 49# coal seam in No. 8 mining area of Xinxing Coal Mine as the research object. The results show that the working face stress field is asymmetrical which is caused by the reserved roadway and the over goaf. After roadway tunneling, features of obvious stress redistribution are formed. The vertical and horizontal stress in the coal seam develop a U-shaped distribution. The vertical stress in the roadway is less than that in the lower roadway, and the horizontal stress is half that in the lower roadway. The phenomenon of high stress “nucleation” appears and becomes more obvious in the process of working face advancing, and the nuclear body disappears after working face advanced to the boundary line. With the working surface advancing, the trend of horizontal stress of gob-side entry retaining decreases gradually and the vertical stress of gob-side entry retaining is less than the original rock stress. The research findings provide a basis for the supporting design of gob-side entry retaining in the deep thin coal seam and the stability control of surrounding rock.
The acoustic emission characteristics of rock specimens under different initial unloading confining pressures were tested to obtain the damage and rupture characteristics of the sandstone unloading confining pressure path. The CT scan and three-dimensional reconstruction of the fractured rock specimens were carried out to study the differences of energy evolution and acoustic emission characteristics during the failure of sandstone under different initial unloading pressures. The results show that the unloading confining pressure has a significant influence on the deformation and failure of the rock. There is a significant yielding platform for the circumferential strain and the bulk strain at the peak of the unloading pressure. The larger the initial unloading pressure is, the greater the axial absorption strain energy, the dissipative energy, and the elastic strain energy are at the peak point. After the stress peak point, the elastic strain can be quickly converted into the dissipative energy for rock damage. The elastic energy released from the moment of rock failure under high confining pressure is more concentrated. The acoustic emission ringing and b value characteristic parameters of the rock have a good correlation with the internal energy evolution of the rock, which better reflects the progressive damage of the rock under low stress and the sudden failure of high-stress unloading.
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.
In underground engineering, the deformation and failure process of the surrounding rock of the roadway is always accompanied by the occurrence of energy. The study of the energy distribution law of the surrounding rock of the roadway plays an important role in its stability. This paper first theoretically analyzes the stress and energy distribution law of the surrounding rock of the roadway, then with the help of numerical simulation method, combined with the existing physical and mechanical parameters, based on the existing support parameters of Dongrong No. 2 Mine, gradually compares and analyzes the distribution of vertical stress and energy under the three support methods of no support, original support, and combined support, and the results found that the vertical stress distribution law under the three support methods is basically the same. High-stress areas appear on the two ribs of the roadway, and low-stress areas appear on the roof and floor. The range of high-stress areas from no support to combined support continues to decrease and becomes more evenly distributed. The energy distribution pattern is basically the same. The overall energy of the coal seam is high. There are high-energy areas at 2 m left and right of the roadway, and the roof and floor energy of the roadway is the smallest. The low energy area extends 5 m up and down, respectively. The range of high-energy areas from no support to combined support is shrinking, and the energy distribution is more uniform.
The water inrush from the roof of the coal mine is closely related to the movement failure of overburdened rock and the height of the water-conducting fracture zone. In this work, based on the research background of water disaster prevention and control of the No. 2 coal seam roofs in Jinxinda Coal Mine, the stability characteristics of overlying rock in the working face are analyzed through combining theoretical analysis and numerical simulation. According to the theory of key strata, the fracture conditions of hard rock and soft rock are analyzed, and the maximum height of the water-conducting fracture zone in the 201 working face is calculated to be 35.72 m. The crack evolution law of composite roofs was simulated and analyzed using discrete element software. It was found that the basic roof (4.50 m thick) and the fine sandstone (7.64 m thick) are the two inferior key strata, and the maximum development height of the water-conducting crack is 36 m, which is basically consistent with the field measured results. Transient electromagnetic exploration technology was used to detect the working face, and nine abnormal areas were found. In order to prevent the influence of water disasters in abnormal areas during mining, drilling verification is carried out in abnormal areas. According to the analysis of drilling verification, there are no water disasters in the geophysical anomaly area, but the management of the roof after mining should be strengthened during mining. The expected research results not only enrich the rock formation control theory and roof water inrush mechanism; they also have important practical significance in guiding the safety production of a coal mine.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.