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短壁胶结充填开采房式遗留煤柱采场结构稳定性控制研究

Study on stability control of stope structural in short-wall cemented backfill mining for recovery of room-and-pillar residual coal

  • 摘要: 房式开采遗留煤柱资源的呆滞和矿山固体废弃的排放严重制约着我国煤炭行业的绿色低碳转型升级。为此,以陕北矿区板定梁煤矿为工程背景,提出了一种"时序协同−煤柱置换"的短壁胶结充填采煤回收煤柱的工艺。首先基于极限强度理论,对房式开采遗留煤柱回收的安全应力进行核算;其次采用数值模拟研究自然垮落法管理顶板回收遗留煤柱过程中的失稳特征及顶板破断对采场稳定性的影响,建立短壁胶结充填采场力学模型,求解出确保直接顶不发生破断的临界充填体强度;最终开展力学试验分析胶结充填体的力学特性、破坏特征及微观特征,并结合实际工程提出了一套完整的短壁胶结充填采煤设计方法。研究结果表明:板定梁煤矿遗留煤柱安全应力值为11.78 MPa,具备安全回收的条件;基于自然垮落法管理顶板回收遗留煤柱的应力、塑性区分布特征及顶板破断分析,发现在回收过程中可能会引发“多米诺”链式失稳效应,并伴随有顶板大面积破断;并进一步提出短壁胶结充填采煤技术置换遗留煤柱,计算得到采场直接顶不发生垮落的临界充填体强度为8.97 MPa;基于此,获取充填材料中煤矸石∶粉煤灰∶水泥∶水的最优配比为3∶3∶1∶1,该配比下矸石颗粒级配较优越,水化产物致密填充骨料间隙,有效减少了孔隙率,显著提升力学性能,可满足板定梁煤矿安全回收煤柱需求;并对试验回收区域的短壁胶结充填采煤工作面生产系统和关键参数进行了可行性设计,并提出确保充填效果的控制措施。研究成果为我国煤炭行业“资源回收−生态保护−固废利用”一体化绿色低碳转型发展提供了可复制的工程范式。

     

    Abstract: The stagnation of residual coal pillars from room-and-pillar mining and the discharge of mine solid waste have severely constrained the green and low-carbon transformation of China’s coal industry. To address these challenges, the Bandingliang Coal Mine in northern Shaanxi as the engineering case study, a novel "time-sequence coordinated pillar replacement" short-wall cemented backfill mining technique was proposed. First, the safe stress for the recovery of residual coal pillars from room-and-pillar mining was calculated based on the limit strength theory. Secondly, numerical simulation was used to study the instability characteristics of the natural collapse method for managing the recovery of residual coal pillars and the impact of roof failure on the stability of the mining area. A mechanical model for the short-wall cemented backfill stope was established, and the critical strength of the backfill material was solved to ensure that the direct roof would not fail. Finally, mechanical tests were performed to analyze the mechanical properties, failure characteristics, and microstructural features of the cemented backfill, and a complete design method for short-wall cemented backfill mining was proposed based on the actual engineering. The results indicated that the safe stress value for the residual coal pillar in Bandingliang Coal Mine was 11.78 MPa, which met the conditions for safe recovery. Based on the stress, plastic zone distribution characteristics, and roof failure analysis during the recovery of residual coal pillars using the natural caving method, It was discovered that the recycling process may trigger a “domino” chain reaction, accompanied by large-scale roof failure. Furthermore, the short-wall cemented backfill mining technique was proposed to replace the residual coal pillars, and the critical backfill strength required to prevent roof collapse was calculated to be 8.97 MPa. Based on this, the optimal mix ratio of coal gangue∶fly ash∶cement∶water in the backfill material was determined as 3∶3∶1∶1. This mix ratio provided superior gangue particle grading, and the hydration products densely filled the gaps between aggregates, effectively reducing porosity and significantly improving mechanical performance, thus meeting the safe recovery requirements for coal pillars in Bandingliang Coal Mine. Feasibility designs for the short-wall cemented backfill mining production system and key parameters in the experimental recovery area were proposed, along with control measures to ensure the effectiveness of the backfill. The research results provided a replicable engineering paradigm for the “resource recovery-ecological protection-solid waste utilization” integrated green and low-carbon transformation and development of the coal industry in China.

     

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