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The gradual depletion of shallow resources necessitates the imperative shift towards deep mining. In deep mining, dynamic disasters, such as rockburst, caused by high in-situ stress and other complex geological environments, have persistently posed a significant challenge to the safe and efficient extraction of deep minerals. Despite the longstanding occurrence of rockburst disasters, they have not been effectively resolved due to limitations in their occurrence mechanisms and monitoring methods. In this paper, the evaluation system and the prevention and control technology of rockburst were systematically summarized and concluded through literature research. The current research progress shows that there are many evaluation systems of rockburst, which can evaluate and predict the grade and tendency of rockburst disasters well. Regarding rockburst prevention and control systems, they can generally be classified into passive and active control technology based on the timing of disaster management and protective mechanisms. The overall planning concept was developed based on mining plan optimization and stress environment reconstruction, providing a new idea and method for rockburst prevention and control in deep mining of metal mines. Finally, taking the deep mining of Sanshandao Gold mine as the background, the advantages and effects of the unloading mining scheme in rockburst control and prevention under the integrated planning concept were verified, which provided an effective reference for the advanced intervention and active prevention and control of rockburst in deep mining of metal mines in the future. [ABSTRACT FROM AUTHOR]

We chose to study the bottom structure stress evolution law in the process of undercut area advancement via the block caving method, reveal the influence law of the undercut rate on the effect of the ore body caving process, and assess the floor stress evolution law in the process of the undercut area with a different undercut rate in order to guide the production of a natural disintegration method under horizontal ground stress and also provide some reference value for rock damage assessment. According to the actual engineering and physical parameters of the mine, a numerical simulation model was created by using finite discrete element software GPI-3D-FDEM, and the Neo–Hookean hyperelastic constitutive model was adopted for calculation purposes. The simulation process follows a backward bottoming approach and monitors and analyses the stress state of the substructure after each bottoming step. The indoor physical model is employed to conduct similar two–dimensional simulation experiments on similar materials, investigating the motion laws of overlying rock layers. The research findings indicate that as bottom blasting progresses, a gradual concentration of compressive stress occurs in the foundation structure ahead of the advancing line. If this stress surpasses the rock mass's shear failure limit, ground pressure failure may ensue. During mineral extraction from the bottom, internal stress within the fractured fault zone significantly diminishes compared to adjacent rock and ore deposits. [ABSTRACT FROM AUTHOR]

The inducers of the chemical or physical factors could affect the gene expression and transcription of strain directly or indirectly. In order to explore the inductive effect of higher alcohol on Galactomyces geotrichum, the G. geotrichum S12, derived from the soil, was induced by five higher alcohols, including n-propanol, n-butanol, isobutanol, nhexanol and isoamyl alcohol. The effects of induction dose and induction time for degradation activity of different higher alcohols by strain S12 and its transforming enzyme were studied. The results showed that the enzyme activity formed by strain S12 was higher when the inducers were chosen as n-hexanol and isobutanol. The optimum induction time was 6 h when n-propanol, n-butanol, isobutanol and n-hexanol were used as inducers. While the optimum induction time of strain S12 and enzyme induced by isoamyl alcohol was 12 h. When n-propanol and n-hexanol were used as inducers, the optimal concentration was 1.5 g/L. While the optimal concentrations of strain S12 and enzyme induced by n-butanol, isobutanol and isoamyl alcohol were 1.0, 0.5 and 2.5 g/L, respectively. The results of native polyacryplamide gel electrophoresis (Native- PAGE) indicated that dehydrogenase formation, molecular weight about 223 kDa, was induced by five higher alcohols. In particular, the strain, induced by hexanol, had much higher capability in degrading five higher alcohols at the same time. The products of the above five higher alcohols after catalyzing by G. geotrichum S12 induced by hexanol were their corresponding acids and esters. [ABSTRACT FROM AUTHOR]

To investigate the self-pulsation characteristics of a liquid-centered swirl coaxial injector with liquid oxygen (LOX) and gas hydrogen (GH2) as the working mediums under supercritical condition, a numerical simulation was employed. The transient simulation of the flow and injection process of cryogenic propellant was carried out using the RNG k − ε turbulence model, VOF model, and Peng-Robinson equation of state. The frequency spectrum of calculated pressure oscillation agreed with the experimental data. The amplitude-frequency characteristics of recess region, LOX, and GH2 paths when self-pulsation occurs were analyzed. The effects of operating parameters, such as the flow rate of LOX or GH2 and the initial GH2 temperature, on the self-pulsation, were evaluated specifically. Results reveal that the self-pulsation results from the periodic variation of pressure and velocity caused by the periodic blocking of annular gas by the liquid sheet. The dominant frequencies of pressure oscillation in the recess region, upstream of LOX, or GH2 path are diverse. But for the points in each region, the dominant frequency is about the same. When the LOX/GH2 mixing ratio increases, the liquid sheet thickness and the number of liquid filaments increase. The position where filaments are massively broken into droplets moves further downstream. For the same mixing ratio, the flow rate of LOX has a greater impact on the atomization features. The pressures corresponding to low or high frequency increase when the initial GH2 temperature raises. The higher temperature would shift the dominant oscillation between the low and high regimes. [ABSTRACT FROM AUTHOR]

The stability of the cemented paste backfill is threatened by the dynamic disturbance during the excavation of the surrounding ore body. In this paper, the computerized tomography (CT) and Split Hopkinson Pressure Bar (SHPB) tests were conducted to explore the initial pore distribution characteristics of the cemented tailings backfill (CTB) and the development of the crack under low impact amplitude. SHPB tests were conducted with impact amplitudes of 34, 37, and 39 mV, respectively. Results show that the initial pores of CTB were steadily distributed with the height of CTB. The CTB contained many initial pores with similar pore size distribution characteristics, and the largest number of pores is between 0.1 and 0.3 mm. Most of the cracks in CTB after low impact amplitude develop and expand along the initial pores, and the damage of CTB mainly exists in shear cracks. A dependence has been established that the dynamic uniaxial compressive strength of the CTB increases, the total crack volume first increases and then decreases, and the number of cracks increases as the impact amplitude increases. The research results can provide a valuable reference for the dynamic performance of CTB under low impact amplitude and the design of mining backfill. [ABSTRACT FROM AUTHOR]

The Mohr-Coulomb elastoplastic model is extensively employed in geotechnical engineering. Despite the well-known nonlinear behaviour of granular cohesionless materials under a wide range of normal stress or confining pressure, the Mohr-Coulomb elastoplastic model continues to be largely used in geotechnical engineering, due to its simplicity and large availability in numerous commercialised software. Its application requires the input of a key parameter, named Poisson's ratio. It is however a big challenge as its value changes with axial strain and confining pressure. In this study, the optimal Poisson's ratio of granular materials for the Mohr-Coulomb elastoplastic model is determined by reproducing the experimental results of stress-strain relationships through numerical modelling with the Mohr-Coulomb elastoplastic model. The results show that the Poisson's ratio μ0.02, corresponding to the slope of the volumetric strain against axial strain curve at 2% of the peak deviatoric stress can be used in numerical modelling with the Mohr-Coulomb elastoplastic model as long as the granular material does not exhibit dilation behaviour. When the material exhibits dilation behaviour, the Poisson's ratio μ0.36, corresponding to the slope of the volumetric strain against axial strain curve at 36% of the peak deviatoric stress, seems to be appropriate in numerical modelling with the Mohr-Coulomb elastoplastic model. In addition, the study also shows that the Mohr-Coulomb elastoplastic model can be used to simulate mechanical behaviour of granular material under small strain, but not appropriate under large strain conditions. [ABSTRACT FROM AUTHOR]