3 / 2023-02-12 19:06:37

巨厚弱胶结覆岩深部开采岩层运动规律及区域性控制研究

巨厚弱胶结覆岩；深部开采；岩层运动与控制；部分充填开采

Compared with the deep mining area of the Yanzhou coal field and the Jining coal field in the east, under the same mining degree, the surface subsidence of coal mining under the ultra-thick and weak cementation overburdens in the deep mining area of the western Dongsheng coalfield is significantly smaller. The existing strata movement theories cannot rationally elucidate its particularity. This phenomenon produces pronounced safety threats to the mining of high-yield and high-efficiency working faces, thereby severely confining the large-scale mining of coal resources under ultra-thick and weak cementation overburdens. Yingpanhao coal mine in Dongsheng Coalfield was studied in this paper: Firstly, the physical and mechanical features and microstructural characteristics of weakly cemented sandstones have been investigated experimentally. Then, the differences in rock mechanical properties, overburden structure characteristics and surface movement and deformation rule were compared and analyzed in eastern-western deep mining areas. This work also identified the influencing factors that caused the surface subsidence of ultra-thick and weak cementation overburdens in deep mining being relatively small. Lastly, mechanical analysis, numerical simulation and physical simulation were applied to learn the surface movement and deformation rule, strata movement and failure characteristics of ultra-thick and weak cementation overburdens in deep mining, and the regional strata movement control method of ultra-thick and weak cementation overburdens in deep mining was proposed. The specific findings can be summarized as follows:

（1）Although the ultra-thick and weak cementation overburdens were weak in lithology, the overall rigidity of the rock strata was relatively large. The uniaxial compressive strength of the Cretaceous Zhidan group sandstone was between 10~20 MPa, but its lithology was weak; The inner fissure of the rock strata was great, but the cracks and joints were barely developed; The cementation was calcareous and insoluble in water, and the mechanical features of the cement were similar to those of the rock particles; The single strata was thick and no folds and faults were grown. Therefore, the above factors cause the overall rigidity of the sandstone of the Zhidan group larger.

（2）Effect of overburden structure changing on the surface movement and deformation rule of ultra-thick and weak cementation overburdens in deep mining: With the increase of mining degree, the control effect of super-thick sandstone on the overburden movement is strengthened at first and then weakened. Due to the control effect of super-thick Zhidan group sandstone, the surface subsidence coefficient decreases by 0.18 at most, 28.2% of the surface subsidence coefficient without control effect. There are obvious differences in the effect on surface movement and deformation rule caused by the alterations in the relative spatial distances and relative order of the main key layer and the sub-key layer. The alterations in the relative spatial distances of the main key layer and the sub-key layer owned a small effect on the surface subsidence rate, the horizontal surface movement coefficient and the main influence angle tangent. The changes in the relative order of the main key layer and the sub-key layer had a huger influence on the surface subsidence rate, and led to a smaller effect on the horizontal surface movement coefficient and the main effect angle tangent.

（3）Influence of horizontal tectonic stress on the surface movement and deformation rule of ultra-thick and weak cementation overburdens in deep mining: Horizontal tectonic stress was one of the chief reasons that the impact range of deep mining was far larger than the current cognition, and it was also one of the key reasons for the small surface subsidence of ultra-thick and weak cementation overburdens in deep mining. The decrease value of surface subsidence coefficient reaches 0.49 at most, 61.3% of subsidence coefficicent of geological prototype. S_w value increases 1110m at most, 205.6% of S_w value of geological prototype. S_u value increases 1710m at most, 247.8% of S_u value of geological prototype.

（4）When D₁/H₀>=3 and D₃/H₀>=3, the surface reached to fully mining. The failure mode of the ultra-thick and weakly cemented overburden was the "beam-arch shell" failure, and the damage boundary was arch-shaped cracks. With the continuous expansion of the mining area, the complete "arch shell" failure was gradually transformed into "semi-arch shell" failure. Before the "arch shell-beam" failure of the ultra-thick and weak cementation sandstone showing, its movement process demonstrated a clear time correlation, and after that, its movement process disappeared in the time correlation, indicating the characteristics of mining and sinking. Due to the "arch shell-beam-arch shell" failure mode of super-thick Zhidan group sandstone, the surface of deep multi-working face mining of the super- thick and weak cementation overburden shows a leaping subsidence.

（5）This paper proposed an approach, partial backfill mining based on the main control layer, for the surface subsidence control and energy-polling reduction of ultra-thick and weak cementation overburdens in deep mining. We investigated the influencing factors and response rule that affected the surface subsidence control and energy-polling reduction effects of partial backfill mining based on the main key layer, and found that the influence degree on the control effect of strata movement from large to small is working face width, filling rate, section pillar width and filling face width, the influence degree of energy-polling from large to small is section pillar width, filling rate, working face width and filling face width. This paper also indicated that the control mechanism of partial backfill mining based on main control layer was the synergy between the composite filling body and the main control layer structure.