浅埋房式残留煤柱失稳致灾机制及防控

Shallow depth room mining goafs are widely spread in the Shendong Coal Field, when mining the second seam which in proximity beneath a room mining goaf, various accidents have happened including immediate roof slice-caving, hydraulic support iron-bound, large area roof percussive caving, wind blast in the room mining goaf and its lower seam, these issues have seriously restricted the safe and efficient mining. At present, domestic and overseas scholars have paid more attentions to the pillar reasonable dimensions design and stability laws, but less focuses on the shallow depth room mining residual pillars instability induced accidents mechanism with the mining dynamic pressure influence. Thus, this project takes the shallow depth room mining goaf and the lower longwall face as the objects, by establishing a "Main roof-Residual pillars-Immediate roof-Hydraulic support" system cusp catastrophic model, the stress distribution and energy evolution laws, and the multi-factors comprehensive criterion of the room mining residual pillars, affected by the lower seam mining, can be revealed, the results will provide a theoretical basis for the instability evolution from individual pillar to large area pillars, and immediate roof slice-caving and hydraulic support iron-bound accidents; by analyzing the key factors result in the pillar instability, the targeted prevention technology can be implemented in the field conditions, ultimately guarantee the safe, efficient and high recovery rate mining in the shallow depth seam in proximity beneath a room mining goaf.

神东煤田存在大量浅埋房式采空区，在其下近距离煤层进行长壁开采出现了直接顶切冒、支架压死、顶板大面积冲击式垮落、房式采空区及邻近下煤层飓风等灾害，已成为制约浅埋煤层安全高效开采的突出难题。目前国内外学者对煤柱合理尺寸及稳定性开展研究较多，但对采动影响下浅埋房式残留煤柱失稳致灾机制研究较少。因此，本项目以浅埋煤层房式采空区残留煤柱及其下方长壁开采为研究对象，通过建立"基本顶-残留煤柱-直接顶-支架"系统尖点突变模型，深入研究房式残留煤柱受下煤层采动影响时的应力分布及能量演化规律，建立煤柱群稳定性多因素综合判据，从而为研究房式采空区个别煤柱及大面积煤柱群失稳、残留煤柱下直接顶切冒及支架压死灾害等提供理论依据；分析导致房式残留煤柱失稳的关键指标，进而提出煤柱群大面积失稳致灾的针对性防控技术，结合现场条件进行工业性试验，确保浅埋房式采空区下近距离煤层安全高效高回收率开采。

浅埋煤层具有埋藏浅、基岩薄、上覆松散层厚的地质特征，与普通煤层开采矿压显现特征不同。神东煤田浅埋煤层存在大量房式采空区，在其下近距离煤层进行长壁开采出现了覆岩裂隙导通地表、顶板切冒、支架压死、顶板大面积冲击式垮落、房式采空区及邻近下煤层飓风等灾害，已成为制约浅埋煤层安全高效开采的突出难题。目前国内外学者对煤柱合理尺寸及稳定性开展研究较多，但对采动影响下浅埋房式残留煤柱失稳致灾机制研究较少。因此，本项目以浅埋煤层房式采空区残留煤柱及其下方长壁开采为研究对象，开展了以下研究：①在石圪台煤矿等浅埋煤层采取了煤体和岩体样品，在岩石力学控制实验室利用MTS815.02电液伺服岩石力学实验系统完成了煤岩块的测试工作，得到了煤岩体的物理力学参数等特征；②提出了房式煤柱稳定性控制模型，基于能量理论采用FLAC3D数值模拟分析了煤柱、顶板能量演化规律及其影响稳定性的主要因素；③进行了浅埋煤层采空区下长壁开采覆岩结构及支架承载特征理论分析，建立了“基本顶—残留煤柱—直接顶—支架”系统结构模型，揭示了浅埋房式残留煤柱下近距离煤层开采支架压死机理，提出了液压支架合理工作阻力确定方法；④通过物理模拟和3DEC数值模拟研究了浅埋房式采空区下近距离煤层长壁开采覆岩运动规律及安全开采技术；⑤采用理论分析、物理模拟和UDEC数值分析方法，研究了冲沟地貌下浅埋煤层开采覆岩运动及裂隙演化规律及顶板控制技术；⑥为防止房式采空区下近距离煤层初采期间发生顶板大面积来压冲击事故，提出了切眼穿采空区深孔预裂爆破强制放顶方法，采用LS-DYNA3D进行了浅埋煤层深孔预裂爆破强制放顶机理研究，并提出了合理控制采高、注砂充填煤房、适当加快推进速度等防控方法，现场应用取得了良好效果。浅埋房式残留煤柱失稳致灾及防控机制研究为确保浅埋房式采空区下近距离煤层安全高效高回收率开采提供了科学依据，对西北矿区复杂条件下浅埋煤层安全高效绿色开采具有重要意义。