Study on bearing characteristics and instability law of coal pillar dams under the effect of mining and water immersion
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摘要:
煤矿地下水库的储水技术已成为我国西部矿区煤炭资源开采与水资源保护协调发展的重要途径之一，而煤柱坝体的稳定性是煤矿地下水库能够安全并长期使用的关键因素。为了探究煤矿地下水库煤柱坝体在复杂条件下失稳特征，基于FLAC3D数值模拟及二次开发，以陕西北部某矿相邻工作面开采及采空区蓄水的水浸作用对煤柱坝体应力演化特征及稳定性的影响展开研究。结果表明：工作面开采完毕后，煤柱坝体应力分布均呈现双峰形，并随煤柱宽度的增加峰值逐渐下降，同时煤柱宽度为20 m时其弹性核区占比小于40%的临界失稳指标，将发生失稳；在采空区蓄水后，水浸作用下煤柱坝体塑性区占比增量呈现“稳定-增大-减小-稳定”的变化规律，能够很好地模拟水浸作用下煤柱坝体的“渗流-弱化-损伤-渗流”的渐进破坏特征；煤柱坝体的应力分布逐渐演化为拱形分布并趋于平均化，应力峰值大幅降低，同时,内部塑性区进一步扩展，弹性核区占比降低，且煤柱宽度的越小降低幅度越大；当煤柱宽度为30 m时，弹性核区占比降低为38.33%，将发生失稳；当煤柱留设宽度为40 m时，煤柱能够保持稳定。
Abstract:Coal mine underground reservoir water storage technology has become one of the important ways for the coordinated development of coal resource mining and water resource protection in western mining areas of China, and the stability of coal pillar dam body is one of the key factors for coal mine underground reservoir to be able to be used safely and for a long time. To investigate the destabilization characteristics of coal pillar dams in underground coal mine reservoirs under complex conditions, this paper is based on FLAC3D numerical simulation and secondary development to investigate the influence on the stress evolution characteristics and stability of coal pillar dams under the sequential action of adjacent workings mining and water flooding in the mining area in a mine in northern Shaanxi Province. The results show that the stress distribution of the coal pillar dam body shows a bimodal shape after the mining of the working face is completed. The peak value gradually decreases with the increase of the width of the coal pillar. At the same time, the elastic core area accounts for less than 40% of the critical instability index when the width of the coal pillar is 20 m, and instability will occur. After water storage in the mining area, the increment of the plastic zone of the coal pillar dam body under flooding shows the change law of “stable-increasing-decreasing-stable”, which can well simulate the progressive damage characteristics of “seepage-weakening-damage-seepage” of the coal pillar dam body under flooding. The stress distribution of the coal pillar dam body gradually evolves into an arch-shaped distribution. It tends to average out, and the peak stress is greatly reduced, while the internal plastic zone is further expanded and the percentage of its elastic core zone is reduced. The smaller the width of the coal pillar is, the greater the reduction is.
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图 3 基于煤柱的水浸软化模型计算流程图
Figure 3. Calculation flowchart of water immersion softening model based on coal pillar
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图 6 不同宽度煤柱坝体垂直应力分布特征与弹性核区占比
Figure 6. Characteristics of vertical stress distribution and percentage of elastic core in the coal pillar dam with different widths
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图 7 渗流作用下不同宽度煤柱坝体的塑性区分布
Figure 7. Plastic zone distribution of coal pillar dam with different widths under seepage effect
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图 8 渗流作用下不同宽度煤柱坝体垂直应力分布云图
Figure 8. Vertical stress distribution of coal pillar dam with different widths under seepage effect
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图 9 渗流作用下不同宽度煤柱坝体垂直应力及塑性区分布特征
Figure 9. Characteristics of vertical stress and plastic zone distribution of coal pillar dam with different widths under seepage effect
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图 10 运行过程中不同宽度煤柱塑性区扩展演化规律
Figure 10. Evolution law of plastic zone expansion of coal pillar with different widths in the process of operation
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图 11 运行过程中煤柱宽度为40 m时黏聚力弱化过程
Figure 11. Weakening process of cohesion when the width of coal pillar is 40 m during operation
表 1 数值模拟中材料参数取值
Table 1 Values of material parameters in numerical simulation
岩性 密度/
(kg·m−3)体积模量/
GPa剪切模量/
GPa内摩擦角/
(°)黏聚力/
MPa抗拉强度/
MPa渗透系数/
(nm·s−1)孔隙率 中粒砂岩 2 500 11.61 9.09 28 1.00 2.30 0.060 0.45 砂质泥岩 2 400 2.57 1.45 26 0.55 0.80 0.006 0.35 粉砂岩 2 500 9.63 8.09 30 2.50 0.84 50.000 0.40 泥岩 2 141 2.21 1.24 24 0.52 0.83 65.000 0.40 细粒砂岩 2 400 2.13 0.93 26 0.45 0.35 0.006 0.30 煤层 1 400 2.13 0.93 25 0.40 0.25 80.000 0.50 
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