The Recent Progress China Has Made in the Backfill Mining Method, Part III: Practical Engineering Problems in Stope and Goaf Backfill

With the continuous innovation and development of science and technology, the mining industry has also benefited greatly and improved over time, especially in the field of backfill mining. Mining researchers are increasingly working on cutting-edge technologies, such as applying artificial intelligence to mining production. However, in addition, some problems in the actual engineering are worth people’s attention, and especially in China, such a big mining country, the actual engineering faces many problems. In recent years, Chinese mining researchers have conducted a lot of studies on practical engineering problems in the stope and goaf of backfill mining method in China, among which the three most important points are (1) Calculation problems of backfill slurry transportation; (2) Reliability analysis of backfill pipeline system; (3) Stope backfill process and technology. Therefore, this final part (Part III) will launch the research progress of China’s practical engineering problems from the above two points. Finally, we claim that Part III serves just as a guide to starting a conversation, and hope that many more experts and scholars will be interested and engage in the research of this field.

Failure Properties and Stability Monitoring of Strip and Column Cemented Gangue Backfill Bodies Under Uniaxial Compression In Constructional Backfill Mining

The strip and column cemented gangue backfill bodies (CGBBs) are the main supporting components in the design of constructional backfill mining for coal mining, which determines the stability of goaf. Previous researches have mostly focused on the mechanical properties of column CGBB, but the mechanical properties of strip CGBB are still unclear. Herein, the uniaxial compression experiments for strip and column CGBBs were conducted to compare the failure properties. The acoustic emission (AE) and two types of resistivity monitoring were used to monitor the damage evolution. The effect of the length-height ratio on the mechanical characteristic of strip CGBB was analyzed by discrete element simulation. The results show that: the strength and peak strain of strip CGBB under uniaxial compression is higher than those of column CGBB, and the strip CGBB shows better ductility. The stress of column CGBB decreases significantly faster than that of strip CGBB at the post-peak stage. The strength and ductility of strip CGBB increase with the increase of length-height ratio. The strip CGBB is destroyed from both ends to the middle under uniaxial compression, and the core bearing area is reduced correspondingly. The AE signal evolution of CGBBs under uniaxial compression before the peak stress contains three stages, and the AE signals of strip CGBB at the peak stress will not rise sharply compared with column CGBB. The resistivity monitoring effect of the horizontally symmetrical conductive mesh is better than that of the axial. The horizontal resistivity increases gradually with the increase of stress under uniaxial compression, and increases sharply at the peak stress, and then drops after the peak stress. The damage constitutive models and the stability monitoring models of the CGBBs are established based on the experimental results. This work would be instructive for the design and stability monitoring of CGBB.

Numerical Simulation and Field Measurement Analysis of Fracture Evolution and Seepage Response of Key Aquiclude Strata in Backfill Mining

Solid waste backfill mining can effectively deal with gangue and other mining wastes, as well as control the movement and damage of rock strata. In this paper, the RFPA2D rock failure process analysis software is used to study the fracture evolution and seepage response mechanism of the key aquiclude strata (KAS) under the conditions of different structural characteristics, interlayer rock thickness, and backfilling ratios in backfill mining. The simulation results show that, in backfill mining, soft rock plays a crucial role in the fracture repair of KAS with different structural characteristics. An increase in the KAS thickness from 15 to 35 m is shown to results in a continuously improved repair of KAS fractures. At the advancing distance of the working face of 50~100 m and the KAS thickness of 35 m, the minimum vertical seepage velocity of 0.06 ‐ 0.78 × 10 − 2 m / s is reached. An increase in the backfilling ratio from 45 to 80% improves the control effect on the overlying strata. A case study of backfill mining in the Wugou Coal Mine located in the Anhui Province of China was conducted. At the goaf backfilling ratio of 80%, the composite KAS’s good control effect was achieved, which minimized seepage and avoided the water in rush phenomena. The above engineering application ensured the safe backfill mining of coal resources.

The Recent Progress China Has Made in the Backfill Mining Method, Part II: The Composition and Typical Examples of Backfill Systems

The backfill mining method is a widely used mining method in the major mines of China, which can maximize the recovery of mineral resources and protect the environment. Currently, major mines in China are starting to build backfill systems to apply the backfill mining method, therefore, Part II reviews the progress China has made on creating backfill systems, of which the main contents include: (1) Composition of the backfill system common in Chinese mines; (2) Typical examples of the backfill system in China. Finally, Part II serves as a guide to begin a conversation, and to encourage experts and scholars to engage in the research of this field.

Physical Modeling of the Controlled Water-Flowing Fracture Development during Short-Wall Block Backfill Mining

Short-wall block backfill mining (SBBM) technology is an effective method to solve the environmental problems in the mining process. Based on the technical characteristics of SBBM technology and the physical similarity criterion, the physical similarity models for comparing the control effects of water-flowing fracture (WFF) development using short-wall block cave mining (SBCM) and SBBM were established, and the deformation and the WFF development of overlying strata above gob were monitored. The test results determined that the composite materials of 5 mm thick pearl sponge+5 mm thick sponge+10 mm thick paper+6 mm thick board were adopted as the similar backfill materials by comparing the stress-strain curves between the similar backfill materials and the original gangue sample. When the backfilling body was filled into the gob, it would be the permanent bearing body, which bore the load of the overlying strata accompanied with the protective coal pillar. At the same time, the backfilling body also filled the collapse space of overlying strata, which was equivalent to reduce the mining height, and effectively reduced the subsidence and failure height of the overlying strata. Compared with SBCM, the test results showed that the maximum vertical deformation, the height of water-flowing fractured zone, and activity range of overlying strata using SBBM were reduced by 91.4%, 82.5%, and 64.9%, respectively. SBBM had a significant control effect on strata damage and WFF development, which could realize the purpose of water resource protection in coal mines.

The Recent Progress China Has Made in the Backfill Mining Method, Part I: The Theory and Equipment of Backfill Pipeline Transportation

The backfill mining method is one of the common methods of mine mining worldwide, due to its capacity to maximize the recovery of mineral resources and protect the underground and the surface environment. Similar to the developing conditions of China’s mining industry, China’s backfill mining technology started late, and the level of its equipment is weak, but its development is particularly rapid. Especially after entering the 21st century, China has paid more attention to mining safety, environmental protection, and the continuous implementation of resources development, China’s backfill mining method has increasingly improved, and the level of filling equipment has gradually reached the most advanced level worldwide, which means China has been making great progress in the equipment of backfill mining method, and in recent years, China has also made great progress in the theory of backfill pipeline transportation. Therefore, Part I mainly focuses on both the theory and equipment of backfill pipeline transportation and the recent progress China has made in is introduced in two sections as follows: (1) the theory of backfill pipeline transportation and (2) the equipment of the backfill mining method. Finally, the authors claim that this paper serves just as a guide, tossing out a brick to get a jade gem, and we hope many more experts and scholars will be interested and engage in the research of this field.