To evaluate the evolutionary processes guiding the formation of the tailings‐water mixtures produced by the instantaneous collapse of tailings ponds and the influence of these on downstream facilities, a 2D simulation model with reasonable boundary and working conditions derived from actual engineering practice was built in this study, and the relationship between dam‐break elevation and impact on downstream facilities was also analyzed to determine the relevant mechanism of influence. Computational results indicated that lowering the dam‐break elevation caused the maximum velocity and flooding depth, along with the flooded area at monitoring points, to gradually increase. The occurrence times of maximum velocity and flooding depth were also gradually moved forward as the breaking elevation was reduced; this effect is directly related to the increase in the total potential energy at the lower break elevations. Further simulations of sand‐prevent dams with different heights located downstream from a tailings pond were carried out to identify methods for mitigating the impact of dam failure. The results revealed that increasing the height of the sand‐prevent dam reduced the production of tailings mixtures. Based on the results, the construction of a sand‐prevent dam with a crest elevation equal to that of the starter dam was recommended.

To solve the high slurry pressure and severe wear at some sections in backfilling pipelines, this study investigates the solution of using an auxiliary pipe to increase the resistance and reduce the pressure of the mine backfilling pipeline. Using computational fluid dynamics, three auxiliary pipe models, a Z-shaped pipe, a S-shaped pipe and a spiral pipe were constructed and the velocity and pressure distribution characteristics of the filling slurry in the auxiliary pipes were analyzed. The function of friction loss in spiral pipes with different pitches and spiral diameters was established, and the amendment equation for calculating the effective stowing gradient was studied when using spiral pipes to increase resistance and reduce pressure. The results show that, compared with the Z-shaped pipe and the S-shaped pipe, the velocity and pressure in the spiral pipe change continuously and steadily, and there is no obvious sudden change in the local velocity and pressure. Therefore, it is difficult to burst the pipe. When the velocity is 2.5 m/s and the vertical height of the pipe is 2.5 m, the friction loss of the filling slurry in the spiral pipe can reach 3.87~21.26 times that in the vertical pipe, indicating that the spiral pipe can effectively play the role of increasing resistance and reducing pressure. The relationship between the friction loss and spiral diameter is a linear function, and the relationship between the friction loss and pitch is a quadratic function. The three are binary quadratic function relationships. The equation for calculating the effective stowing gradient is obtained, which provides a convenient method for engineering applications and industrial design.

This work extends research on the mechanism of electromagnetic radiation (EMR) induced by coal or rock fractures to the category of microscopic dynamic experimental research. A custom-made three-point bending test system and atomic force microscope (AFM) were integrated to obtain the microdynamic loading test system. The notched coal samples were prepared specially. The dynamic propagation of new microcracks in coal samples was measured, and the propagation velocity was calculated. The morphology and electro-mechanical characteristics of new microcracks were tested. More importantly, the causes of the changes in the electro-mechanical characteristics before and after fracture were analyzed, and the effects of these changes on the EMR were discussed. The results showed that the average propagation velocities during the same time interval are 9.5 μm/s, 12.1 μm/s, and 16.2 μm/s. The elastic modulus of the material at the microcrack edge is generally smaller than that of the material in other locations, while the adhesion and deformation are larger. Moreover, the closer the material is to the microcrack, the higher its surface potential. The electrons generated at the microcrack edge and emitted into the atmosphere, which made the greater potentials of the microcrack edge. Many electrons with different velocities and directions migrate in similar parallel-plate capacitors, which are formed by the relative microscale surface of the coal microcrack tip and have different field strengths, resulting in EMR with complex frequencies and different intensities. This study provides a micro-dynamic experimental basis for research on the electromagnetic radiation mechanism.

The strength evolution law of concentrated full tailings is closely related to the storage construction method, especially the growth law of shear strength with curing age. This study aims to investigate the influence of curing materials on the shear strength of full tailings and reveal the change law of the shear strength of concentrated full tailings with the curing age. Therefore, we carried out a comparative triaxial shear test between pure full tailings and concentrated full tailings with different curing ages. The test results show that concentrated full tailings had a 70.7% higher cohesion and a 10% larger internal friction angle (IFA) than that of pure full tailings at the age of 0 days. Moreover, the concentrated full tailings cured for 3 days had a 170.2% higher cohesion and a 12.1% larger IFA than that cured for 0 days. In addition, the concentrated full tailings cured for 7 days had a 149.4% higher cohesion and a 12.1% larger IFA than that cured for 0 days. The stress-strain curve exhibits that the shear strength of full tailings is significantly influenced by the curing material and curing age. The stress-strain curve gradually moved from strain hardening to strain softening as the curing age increased, and the failure curve had two steps. This indicates that the specimen still has a certain shear capacity despite having a shear zone. The entire specimen instantly fails when the strain exceeds that capacity. The results of this study can be used as scientific bases for the design and construction of the surface storage structures of concentrated full tailings.

This article introduces a technology of integrated presplitting blasting, which can be applied to a new nonpillar coal mining method (i.e., Gob-side Entry Retaining by Roof Cutting (GERRC)) under the condition of thick and hard roofs. First, the new nonpillar coal mining method emerging in China is explained. Then, the concept of integrated presplitting blasting was put forward, and the mechanism of the technology was explained by the method of numerical simulation. Through a mining case with a thick hard limestone roof, the relevant design of nonpillar mining and the design parameters of integrated presplitting blasting are explained in detail. After field practice verification, from the construction process and test results, as well as combined with underground pressure observation and analysis, it shows that technology and design are reasonable. This research supplements the mining technology system of coal mining engineering and the proposed technologies and methods have strong applicability, especially for related coal mines nonpillar mining and safe and efficient mining.

The existing empirical formulas concerning draining systems are complex in their expression: there are difficulties in locating the intersection point among different flow patterns and parameters vary depending on the water level, resulting in a large amount of data to be processed and low calculation efficiency. To solve these problems, a “simplification-fitting” method was proposed herein to calculate the discharge capacity of a window-type draining well, and optimal and reasonable locations were selected as discrete points of water level to deduce the increasing progressive relationship of free flow discharge capacity among discrete points according to the window size and longitudinal layout of window-type draining wells. Additionally, the algorithm simplified the discharge formulas of half-pressure flow and pressure flow and defined the convergence criteria for water level-discharge capacity to further simplify the expression of pressure flow. The comparison and contrast between the simplified calculation method and empirical formula method show that the method herein is of high precision. It is able to resolve the shortcomings of the traditional theoretical formula method in solving the discharge capacity curve of a window-type draining well and simplify the algorithm integration.