大倾角走向长壁工作面局部充填无煤柱开采理论与技术

Theory and technology of partial backfill non-pillar mining in longwall faces of steeply dipping coal seam

大倾角煤层走向长壁采场围岩结构及应力环境异化,工作面不同位置“支架-围岩”系统的构成因素及灾变模式不同,导致工作面安全事故频发、煤炭采出率较低、巷道掘进率高。通过对大倾角采场围岩采动力学行为的分析,提出了大倾角走向长壁工作面局部充填无煤柱开采技术构想,工作面走向推进过程中沿倾向对采空区下部进行局部充填,充填体既与巷旁支护作用形成沿空巷道,取消区段保护煤柱,实现大倾角煤层无煤柱开采,又增大了工作面倾向下部充填压实区长度,加强了工作面“支架-围岩”系统稳定性。根据大倾角走向长壁采场特点,优选确定了大倾角膏体局部充填工艺,设计了大倾角局部充填回采系统、采充工艺。并采用理论分析、模拟实验、数值计算等相结合的方法,分析了局部充填对大倾角走向长壁采场围岩采动力学行为的调节机制。结果表明:充填体影响基本顶岩梁的变形破坏及采场倾向下侧煤岩体承载特征,基本顶、运输巷顶板变形量及运输巷倾向下侧煤岩体所受约束均随充填长度的增大而减小;为防止采空区未充填区悬顶灾害,充填长度不应超过工作面长度的1/3。局部充填体限制了工作面下部区域顶板破断,降低覆岩关键域形成层位,形成稳定的巷帮,减小沿空留巷围岩变形量;同时工作面倾向下部充填区长度增大,中、上部围岩结构不稳定区域的长度缩小,“支架-围岩”系统稳定性提升。充填体改变了采场围岩应力传递路径,承担了部分覆岩载荷,工作面下侧支承压力及超前支承压力均随充填长度的增大而减小,工作面倾向下部充填区域的超前支承压力降幅最大,沿空巷道及工作面应力状态得到改善。大倾角走向长壁工作面局部充填无煤柱开采技术具有提高资源采出率、降低掘进率、缓解采掘接替紧张、加强工作面“支架-围岩”系统稳定性等优势。

The structure and stress environment of the surrounding rock at the longwall mining area in the steeply dipping coal seam are alienated,and the composition factors and disaster modes of the“support and surrounding rock”system in the working face are affected.This leads to some frequent safety accidents in the working face,low coal extraction rate,and high roadway excavation rate.This paper analyzes the mining mechanics behavior of surrounding rock of in the steeply dipping coal seam and proposes a technological concept of partial backfill non-pillar mining in the longwall faces of steeply dipping coal seam.During the process of advancing the working face,partial backfill is carried out along the inclined direction in the lower part of the goaf.The filling body not only forms a gob-side roadway with the support effect of the roadway side,but also eliminates the protection coal pillar,achieving a non-pillar mining.At the same time,the length of the filling and compaction area at the lower dip of the working face is increased,enhancing the stability of the“support and surrounding rock”system of the working face.Based on the characteristics of the longwall mining area in the steeply dipping coal seam,the partial backfill process of the steeply dipping coal seam paste was optimized and determined.And the partial backfill recovery system and mining and filling process in the steeply dipping coal seam were designed.By using a combination of theoretical analysis,simulation experiments,and numerical calculations,the regulatory mechanism of partial backfill on the mechanical behavior of surrounding rock at the longwall mining area in the steeply dipping coal seam was analyzed.The results show that the filling body affects the deformation and failure of the main roof rock beam,as well as the bearing characteristics of the coal and rock mass on the lower side of the mining area.The deformation of the main roof and the roof of the head entry,as well as the constraints on the coal and rock mass on the lower side of the head entry,all decrease with the increase of filling length.In order to prevent the hanging roof disaster in the unfilled area of the goaf,the filling length should not exceed 1/3 of the working face length.The partial backfill body restricts the fracture of the roof in the lower area of the working face,reduces the formation layer of the critical zone of the overlying rock,forms a stable roadway,and reduces the deformation of the surrounding rock gob-side roadway retained.At the same time,the length of the filling area at the lower part of the working face increases,and the length of the unstable area of the middle and upper surrounding rock structures decreases,improving the stability of the“support and surrounding rock”system.The filling body changes the stress transmission path of the surrounding rock in the mining area,bearing part of the overlying rock load.The side abutment pressure on the lower side of the working face and the front advanced pressure both decrease with the increase of filling length,and the front support pressure in the lower filling area of the working face has the greatest decrease.The stress state of the gob-side roadway and the working face is improved.Technology of partial backfill non-pillar mining in the longwall faces of steeply dipping coal seam has the advantages of effectively improving resource recovery rate,reducing the roadway drivage ratio,alleviating the tension of mining and replacement,and strengthening the stability of the“support and surrounding rock”system in the working face.It is of great scientific significance for guiding the green,safe,and efficient mining in the steeply dipping coal seam.