The mining of layered soft bauxite under coal seams (BCS) will cause serious underground goaf disasters and surface Bayer process red mud (BRM) pollution. In order to realize the safe and efficient mining of BCS, the feasibility of recycling BRM as a backfilling aggregate was explored. A series of tests were conducted to prevent the pollution diversion of BRM from surface storage to underground goafs, and a numerical simulation analysis of the backfilling mining process was carried out based on FLAC3D to protect the overlying coal seam. The results show that: under the action of encapsulation, solidification and inhibiting precipitation from cementitious materials, the leaching concentration of harmful substances in red mud-based cemented backfill (RCB) can be reduced 70% more than fresh BRM. Mining disturbance redistributes the in-situ stress field of overlying strata; normal backfilling can not only reduce the pressure stress of pillars, but also release the tensile stress in the roof and floor from +0.4956 MPa to −0.1992 MPa, effectively preventing roof subsidence. Since the creep damage process of past backfill will absorb and dissipate lots of energy, the disturbance range caused by backfill mining is controlled within 3 m, which is only 10% of the open-stope method.
In the mining industry, with numerical simulation analysis of stope roof stability, stope exposed area computation, and pillar buckling collapse simulation, backfill body creep damage mechanism research is becoming the most popular method in the field of backfill mining techniques. In this paper, we first summarized and analyzed the current application status and the existing problems of numerical simulation for solving mining engineering technical problems; then, based on the practical engineering problems of mining phosphate rock resources under high and steep rock slopes (HSRS), we carried out a true-3D numerical simulation study for different underground mining methods, to determine the appropriate mining method. Therefore, this paper, taking Dingxi Mine in China as an example, highlights the advantages of the backfill mining method with a high and steep slope; meanwhile, it also points out how to improve the accuracy of a numerical simulation and make it more consistent with the actual situation of the mining engineering application site. This paper only serves as a guide, in order to start a conversation, and we hope many more experts and scholars will become interested and engaged in this field of research.
To extract the 6.3 million tons of high-quality phosphate resources, a stability analysis and confidence level evaluation of backfill mining under high and steep rock slopes (HSRS) were conducted using the Slide software and a Monte Carlo simulation. The geological model of HSRS was constructed based on a geotechnical investigation. A series of laboratory tests were conducted to obtain the engineering parameters of the rock mass, and the mechanism of action of the backfill mining method was analyzed. After the stability analysis, the average safety factors of HSRS for normal operation are 1.575 (backfill method) and 1.509 (open-stope method), and for seismic conditions, they are 1.470 (backfill method) and 1.380 (open-stope method). According to the confidence level evaluation, the average failure probability of HSRS by using the backfill mining method is 0.0143. The results showed that using the backfill mining method under HSRS had better seismic stability and lower potential levels of destruction than using the traditional open-stope mining method. In addition, the backfill mining method can prevent the development of a circular failure surface, reduce the destructive effect of mining to a minimum, and maintain the lower failure probability of HSRS.
The stability of mine slopes is an important factor influencing the orderly production of mines and the safety of people’s lives and property. The stability of slopes can be effectively determined by means of three-dimensional simulation analysis. Some 3D simulation analysis methods are based on 2D analysis, and are still essentially 2D analysis methods, whereas this digital simulation analysis uses a true 3D analysis method. This method can reflect the overall slope stability of the mine in a more realistic way, and at the same time, the situation of the selected sections can be observed, making the analysis more scientific and rigorous. This study takes the Shizhuyuan Nonferrous Metal Mine as an example and studies the safety stability of mine slopes through true 3D safety analysis. The results show that the open-pit slopes of the Shizhuyuan mine are stable. The overall model results show that there is only a small amount of tensile damage and no penetration; the section results show that the absolute value of tensile stress is generally small, with a maximum of 1.45 MPa being less than the tensile strength of the material (7.04 MPa). After the model monitoring simulation, it is found that the displacements of each monitoring point are in the process of fluctuation and then stabilisation, which can also indicate that the slope is finally in a stable state. Comparing the above results with the conclusions obtained from the 2D analysis method, the conclusions are found to be in general agreement, indicating that the true 3D simulation analysis method is effective and feasible.
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.
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