Gongcheng Li

With the rapid development of industry, landfill and other environmental problems have arisen due to the coal mining and industrial solid waste generated during coal extraction and industrial production. In this study, coal gangue was utilized as the filling aggregate, along with industrial solid waste as the principal constituent, supplemented by cement, to develop a novel type of cementitious material and address environmental problems arising from the storage of solid waste. The impacts of sodium silicate, lime, and cement on the excitation characteristics and micro-evolution of steel slag–slag-based composite cementitious materials were investigated through experimental proportioning. The mineral composition, chemical composition, particle size distribution, microstructure, and hydration products of the filling materials were analyzed through XRD, XRF, a laser particle size analyzer, and SEM. The results show the following: (1) When the mass ratio of steel slag, slag, cement, sodium silicate, and lime is 30:38:15:2:15, the compressive strength of the Cemented Gangue Filling Body (CGFB) reaches the optimum level. At this juncture, the compressive strength of CGFB at 3 days is 2.16 MPa, and that at 28 days is 4.18 MPa. (2) Na₂SiO₃ and lime can activate the latent active substances within slag and steel slag, generating C-S-H gel and AFt through hydration reaction. (3) As the curing time escalates, the microstructure of the filling body becomes increasingly compact, and the porosity decreases from 10.5% to 3.8%. This study not only presents a new technical means for the resource treatment of solid waste such as coal gangue but also provides powerful support for the development and application of mine filling materials.

During excavation in a deep tunnel, dynamic disaster is an extremely severe impact failure. The necessity of an energy-absorbing support system is analyzed for different characteristics of dynamic disaster (rockburst) failure. The energy-absorbing support system design includes a combination of early-warning, energy-absorbing bolts, and other components. This support system is designed to meet the energy requirement of a rockburst disaster based on an early warning. The energy-absorbing rockbolt uses the stepwise decoupling technique to realize the brittle-ductile transition of the structure, which is referred to as a stepwise decoupling rockbolt (SD-bolt). The ultimate force, ultimate deformation, and energy were calculated as 241 kN, 442.3 mm, and 95.89 kJ under static pull-out load. Monitored by a microseismic system, the support system was tested by moderate rockburst disaster impact on site. Considering similar rockburst disaster failure cases, this energy-absorbing support system can reduce rockburst disaster damage to a certain extent and improve overall safety during deep engineering construction.

Gravity thickening is an important aspect to solve numerous environmental and safety problems that were created by tailings discharging at low solid concentrations. Furthermore, in order to efficiently facilitate the separation of released water and solid sediments, a continuous thickening system with ultrasonic equipment has been used to investigate the thickening performance of copper‐mine tailings under different ultrasonic frequencies (16 kHz, 20 kHz, 22 kHz, 25 kHz, and 28 kHz). After freeze‐drying treatment, the underflow samples are imaged using the scanning electron microscope (SEM); then, the structure of floc or aggregates in the SEM images is quantifiably analyzed using the software of Image J. Results show that the underflow concentration increases as the ultrasonic frequency increases and decreases afterwards. A linear logarithmic function can explain the relationship between underflow concentration and run time at a certain ultrasonic. The underflow concentration is maximized at 64.47 wt. % when the ultrasonic frequency is 22 kHz. Based on the analysis on the microstructure of underflow samples, the minimum pore average size and pore average fraction are obtained when the ultrasonic frequency is 22 kHz, implying that 22 kHz is the optimum ultrasonic frequency combining the results of the underflow concentration.