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Based on the geological condition of Luohe Formation sandstone aquifer above the deep working face of 4# coal in Gaojiapu Mine, Binchang Mining area, the relationship between aquifer and dynamic disaster breeding is discussed. Firstly, the formation and its setting condition of the aquifer above 4# coal seam are introduced. Based on field water inflow monitoring data, we examined the relationship between the resistance of the support and the change of water inflow. The temporal and spatial correlation between micro seismicity and water movement is analyzed and identified, which will offer significant value for the early-warning of the dynamic hazards and water inrush. We expound the dynamic and static load of confined water movement on the working face after the increase of water inrush, and point out that it is important to pay more attention to the dynamic disaster risk of the working face after the water surge.

Deep coal‐rock formations are subjected to complex stress environments characterized by high static stresses and dynamic disturbances. To study the damage, fracture, and energy evolution characteristics of coal‐rock under dynamic–static combined loading, a new multiscale constitutive model for coal‐rock under dynamic–static combined loading is proposed based on micromechanics, and it is implemented into the LS‐DYNA solver. A numerical model of coal‐rock Split Hopkinson Pressure Bar under dynamic–static combined loading is established using LS‐DYNA, and research on the mechanical and energy evolution characteristics of coal‐rock under one‐dimensional and three‐dimensional dynamic–static combined loading is conducted. The results show that under one‐dimensional dynamic–static combined loading, with the increase of precompression, the dynamic peak stress linearly decreases while the combined peak stress linearly increases, and the dissipated energy of the specimen shows a decreasing trend. The fracture patterns of the coal‐rock specimen include internal shear fracture and external tensile fracture, and eventually, these two modes of fracture intersect to form macroscopic mesh cracks. As the axial pressure increases, the degree of specimen fragmentation gradually increases. Under three‐dimensional dynamic–static combined loading, with the increase of preconfining pressure, the stress–strain curve of the specimen will transition from "stress drop" to "stress rebound" after the peak. The peak stress increases with the increase of confining pressure, and the energy dissipation density of the specimen increases first and then decreases with the increase of confining pressure. With the increase of confining pressure, the hoop deformation of the specimen plays a constraining role, and the degree of specimen fracture gradually weakens, and the time of fracture occurrence gradually delays. The research results contribute to revealing the mechanical and energy mechanisms of rockburst disasters in deep coal mines. [ABSTRACT FROM AUTHOR]

Moisture content of rock/coal can change its mechanical properties and absorption capacities, which can directly affect gas diffusivity, change the stress distribution and hence cause significant impacts on the overall gas or coal extraction process. Observation of the water penetration process and water distribution in the coal matrix will be beneficial for the understanding of the fluid-solid coupling mechanism in hydraulic fracturing, aquifer cracking and coal seam infusion. However, the observation of water penetration process and the determination of water distribution mode were hard to be non-destructively achieved as coal is a non-uniform, inhomogeneous and un-transparent material. µ-CT imaging, which is based on variation of X-ray attenuation related to the density and atomic composition of the scanned objects, enables a four-dimensional (spatial-temporal) visualise of the heterogeneous and anisotropic coal samples. The primary aim of this paper is extending the application of µ-CT imaging to explore the moisture penetration and distribution within coal samples during water infusion process, which has been reported by very little literature. The working principle and procedures of CT imaging was firstly introduced. Then, the determination equation of moisture distribution based on density profile was established. The CT determined moisture content has been compared with weighting method for verification. The paper has demonstrated that µ-CT can be used for non-destructively imaging the moisture distribution within coal samples. [ABSTRACT FROM AUTHOR]

In order to prevent the rock burst caused by horizontal sublevel mining of a steeply inclined extra-thick coal seam, the mechanism of rock burst induced by the superposition of dynamic and static loads and the corresponding prevention measures were proposed. Taking Yaojie No.3 coalmine in Gansu Province as the engineering background, the results show that the high concentrated stress caused by the asymmetric distribution of mining stress is the source of static load for rock burst, while the strong dynamic stress caused by the overburden fracture and structural instability is the main source of dynamic load for rock burst. When the total stress reaches the critical stress of large-scale instability of coal-rock mass, the rock burst will occur. Based on the characteristics of dynamic and static load sources, a trinity rock burst prevention and control technology system was established, which comprehensively adopted the deep-hole pre-split blasting in roof for controlling dynamic load, blasting of roadway side and bottom coal or unloading static load by large diameter borehole. The above prevention measures have been successfully applied to the working faces in No.5 mining district of Yaojie No.3 coal mine.

Mining-induced far-field mine tremors, which often cause strong ground tremors, are receiving more attention due to their increasing occurrence. Investigating the rock burst risk of roadway caused by those tremors is crucial to ensure production safety. In this study, Variational Mode Decomposition was used to investigate the wave characteristics of strong mine tremors. The propagation and attenuation of these tremors were explored using the dynamic analysis of Flac3d. The amplification factor was introduced to assess the impact of these tremors on roadways. Plastic zone volume increment and Brittle Shear Ratio (BSR) are used to assess the roadway failure and the rock burst potential caused by these tremors, respectively. The main findings are as follows: 1) Compared with the main frequency of near-field mine tremor waveform, the far-field mine tremors waveform are mainly low frequency below 5 Hz; 2) In the simulation, peak vibration velocities of P-wave and S-wave follow a power-law decay as the propagation distance increases, with P-wave attenuating faster than S-wave; 3) Under similar conditions, P-wave induce higher vibration velocities than S-wave, but S-wave generally exhibit a greater amplification factor than P-wave; 4) When the direction of dynamic load is consistent with the direction of maximum principal stress, the rock burst potential of roadway is higher, which explains the phenomenon that the rock burst potential of roadway under S-wave loading is higher than that under P-wave. [ABSTRACT FROM AUTHOR]