To study the effect and mechanism of coal-rock underground impact pressure prevention and control under the influence of upper protective layer mining. In this paper, the research is carried out based on four factors, namely, the mining stress environment, the mechanical strength of coal and rock, the dynamic load disturbance effect of mining, and the energy loss space of coal and rock. Theoretical calculation and analysis, rock mechanics test, physical similar simulation test and on-site industrial experiments are adopted to study the stress distribution of the coal rock below the influence of the mining of the upper protective layer, overlying strata migration, and the law of mine pressure behavior. The results show that after the mining of the upper protective layer, the vertical stress of the coal rock body under the mined-out area increases with the depth, and the horizontal compressive stress in the shallow area gradually decreases with the increase of depth. In contrast, the horizontal tensile stress in deep areas gradually increases with the depth increase. The uniaxial compressive strength and impact energy index of the coal rock both decrease with the increase of the mining intensity of the upper protective layer. The mining of the upper protected layer will weaken the overburden structure of the mining field of the protected layer, and will reduce the breaking span and disturbance intensity of the key layer in the protected layer. The mining coal rock body in the process of upper protected mining experienced three stages of advanced stress concentration, the rapid growth of pressure relief, and the slow recovery of pressure relief, and the stress release rates all decreased with the increase of depth. The results of the study can provide an important reference value for the prevention and control of underground impact pressure and other disasters in the upper protective layer mining of closed-distance coal seam groups.

A single load compression test of rock-coal-rock assemblages (RCRs) containing coal bodies with different inclinations was carried out with the research background of mining deep, large-steep coal seams. It was found that the larger the inclination angle of the coal body in the RCR samples, the larger the compaction stage of the samples and the smaller the uniaxial compressive strength value. In addition, both the maximum acoustic emission (AE) energy of the samples and the cumulative AE energy at the moment of destruction decreased with the increase of the inclination angle of the coal body in the form of exponential relativities. Also, the input energy and ultimate elastic energy of the samples at the peak stress moment decreased with increased inclination angle of the coal body. Furthermore, both of them changed with the inclination angle of the coal body in accordance with the exponential relationship; meanwhile, when the applied load exceeded the peak strength, the dissipative energy of the RCR samples increased rapidly due to the loss of load-bearing capacity. At the peak moment, the percentage of dissipated energy of the samples increased exponentially with the increase of the inclination angle of the coal body. This study has certain reference significance for the prevention and control of dynamic disasters during the mining of large angle coal seams.

In order to safeguard the surface structures from mining damage while optimizing the liberation of coal resources under the dense surface buildings of the Cedi River coal mine. Considering that the analysis of the structure and type of surface buildings and the geological mining conditions of the mine, a wide strip mining design with a retention width of 70 m and a mining width of 50 m was finally determined by using the pressure arch theory and Wilson’s theory, combined with the actual layout of working faces 51,002, 51,004 and 51,006 at the site.The strip mining design is verified by probability integral method and FLAC^3D numerical simulation calculation respectively, The findings indicate that the highest value of earth surface subsidence created by the mining of the wide strip is 210 mm, the surface horizontal deformation value is 1.0 to − 1.4 mm/m, the damage to surface buildings is less than Level I, which satisfying the prerequisites of the surface building protection level, and can realize the continuous advancement of mine 51,002, 51,004 and 51,006 working faces, The coal pillars of the retained strip have sufficient support strength and long-term consistency, and the movement and deformation of the overburden after mining will not cause undulating subsidence of the surface, which effectively solve the mine's technical difficulties in safely coal mining under surface buildings.

In order to study the regularity of overburden deformation and mining pressure changes in the stope. Take the geological conditions of Hanglaiwan coal mine in Yushen mining area as the background, a 3000mm×1340mm×200mm physical similar material model was established in laboratory. Eight fiber Bragg grating sensors were embedded in the model, used to monitor the movement and deformation of the overburden key stratum and the change of mining abutment pressure in real time and then to determine the influencing factors and strain transfer coefficients of the fiber grating through theoretical analysis and calibration experiments. The results show the following. (1) The changes in value, position, and shape of the strain can reflect the dynamic evolution process of bending deformation, breaking, and rotation of the key strata. When the key layer breaks for the first time, the strain curve shows a peak shape; when the key layer breaks periodically, the strain curve of the fiber grating sensor showed a plateau shape for a period of time. (2) The strain curve has a good corresponding relationship with the change in supporting pressure. When the strain curve of the fiber Bragg grating sensor was at the trough stage, the abutment pressure was at the peak stage, with the increase of sensor buried height, and the supporting pressure and the strain value had a linear relationship within the range of the advanced abutment pressure. The conclusion shows that the fiber Bragg grating sensor monitoring technology has good effect on the internal strain and key supporting pressure monitoring of the overburden in the model test; it provides new monitoring methods and means for the model tests.

To study the influence of different geological and mining factors on the decompression effect of protective layer mining, a numerical simulation was carried out using FLAC^3D numerical software. Taking the Hulusu coal mine as the engineering background, numerical simulation studies were carried out under different mining heights, working face lengths, interlayer lithologies and layer spacing by using FLAC^3D numerical software, and the effects of different geological and mining factors on the degree of decompression and the scope of decompression were quantitatively investigated through the control of single‐factor variables. The results show that: the stress at the critical depth of impact ground pressure is 16.44 MPa, and the coefficient of unloading degree C = 0.5 is the indicator of sufficient unloading; the unloading effect of the protected layer decreases with the increase of layer spacing, lithological strength, and length of the working face, and increases with the increase of mining height; the geological and mining parameters of the protected layer show a functional relationship with the critical depth of the unloading, and the order of the influence of pressure relief effect is layer spacing > mining height > interlayer lithology > working face length. The results of the study are very important for the determination of the mining parameters of the protective layer, the estimation of the protective effect, and the design of the management programme of impact pressure.

The present situation and influencing factors involved in rib-spalling at a fully-mechanized coal mining face with soft and unstable seam were analyzed. The stress characteristics and the mechanism of rib spalling were modeled. Several kinds of control principles and methods were proposed, after the comprehensive comparative analysis, the measure of coal wall injection Marithan powder was conducted, comprehensive prevention and treatment measures to optimize the parameters of fully mechanized mining face for aids had been adopted. Field test results show, after the implementation of comprehensive prevention and control measures of coal wall rib-spalling, the serious rib-spalling for the depth more than 0.7 m has been completely eliminated, and the range of rib-spalling reduced to 5% from 35% of the length of the working face. The occurrence probability of rib spalling were significantly reduced, and to ensure the normal mining of working face, economic and safety benefits were significantly improved.