After deep mining, the discontinuous deformation characteristics of roadway roofs become more and more obvious, resulting in the emergence of separation fractures in the rock mass, which seriously affects the stability of the roof rock mass. By taking the air return roadway 21204 (ARR 21204) in Hulusu Coal Mine as the engineering background, this article reveals the discontinuous deformation characteristics of deep buried roadway roofs through field research, numerical simulation, theoretical analysis and engineering practice. After roadway excavation, the rock masses in different shallow roof horizons show different degrees of stress unloading, resulting in the occurrence of discontinuous deformation phenomena in rock masses. With the rise of the roof rock horizon, the degree of discontinuous deformation fades away until a continuous deformation zone with small deformation and stable rock strata appears. In addition, with the increase in the roadway buried depth, the extent of the discontinuous deformation of the roof and its extended range tend to increase. In view of the discontinuous deformation control of the roof, the technology of linkage control of thick layer cross-boundary anchorage is proposed. By establishing the thick anchorage ring of the roof, the bolts cross the discontinuous deformation zone to support the stable rock strata in the deep continuous deformation zone, thereby realizing the linkage control of the large and small displacement of the rock masses in these two zones and limiting the progressive damage of the roof rock mass from shallow to deep. The industrial test shows that the scope of the separation fracture zone on the roof is controlled at the shallow stratum of 0.85 m due to the great decrease in the surface displacement of roadway, which effectively restricts the progressive upward extension of the discontinuous deformation zone of the roof. The research results can provide references for the safe and efficient control of roadway roofs under deep mining conditions.
In response to the shortcomings of the small support scope of single anchor cable and failure to fully utilize the joint anchoring for surrounding rock, this study summarizes the classification of basic support forms for coal mine roadway surrounding rock and clarifies the main composition and mechanism of anchor cable beam-truss structure. A mechanical model of roadway roof beam under the conditions of no support, single anchor cable support, and anchor cable beam-truss structure support at both ends of the roadway is constructed, and the force and maximum bending moment of roadway roof beam under different support types are compared and analyzed. The study clarifies the bending moment reduction rate of anchor cable beam-truss structure relative to unsupported and single anchor cable support and combines numerical simulation to analyze the response laws of anchor cable beam-truss to prestress distribution and stress shell in roadway surrounding rock. Based on the on-site engineering application of a typical large-deformation mining roadway in a deep coal mine, the important role of anchor cable beam-truss structure in ensuring the safety and stability of surrounding rock in deep high-stress and intense-mining large-deformation roadway is revealed, providing technical references for surrounding rock control of similar conditions in deep roadways.
When mining the upper protective coal seam to liberate the neighboring coal seam with outburst dangerous,the pressure-relieved gas of the liberated seam will pour in goaf and face of the protective seam,which will increase the difficulty of gas control working of the protective seam face.In case of conditions permitting,the pressure-relieved gas drainage of the liberated seam directly can reach twice the result with half the effort.Accordingly,the maximum damage range and depth of the floor can be calculated according to the floor damage theory when mining coal,presenting the gas drainage method of liberated seam in the floor of the upper protective seams through downward-boreholes,and giving the drainage borehole layout design scheme.
Due to crustal movement, coal-bearing strata weather and oxidise when exposed to the atmosphere and water. The unique geological characteristics of the rock in efflorescent oxidation zones lead to variations in lithology, weak rock, and large failures due to deformation. This paper analyses the variable physical mechanics and microstructural characteristics of efflorescent-oxidised coal rock using the UDEC numerical simulation software. The software is used to study the gradual development, dynamic expansion, and deformation of cracks in the material surrounding efflorescent rock tunnels. These numerical simulations reveal information concerning the evolution of surrounding rock attenuation, strength, and deformation. The destruction and causes of roadway failure were also analysed, and optimisation measures were proposed. The results from this study have applications for other research concerning roadway failure, deformation mechanisms, and the addition of appropriate supports.
On the basis of analysis and comparison of the strata behavior and simulation from the caving mining of deeply inclined coal seam in Xin Zhuangzi colliery,It has illustrated the strata behavior regularity of the fully mechanized caving workface.The study is of great importance to strengthen controlling coal slide and roof fall maintain rationally the roof and extending technique in deeply inclined coal seam.
According to the geological conditions of 6# coal seam and 8# coal seam in Xieqiao Coal Mine, reasonable entry layout of lower seam in multi-seam mining has been studied by FLAC3D numerical simula- tion. Three ways of entry layout including alternate internal entry layout, alternate exterior entry layout and overlapping entry layout has been put forward for discussing on reasonable entry layout. Then stress distribu- tion and displacement characteristics of surrounding rock have been analyzed in the three ways of entry lay- out by numerical simulation, leading to the conclusion that alternate internal entry layout pattern, which make the entry located in stress reduce zone and avoid the influence of abutment pressure of upper coal seam min- ing to a certain extent, is a better choice for multi-seam mining. The research results herein can offer beneficial reference for entry layout with similar geological conditions in multi-seam mining
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