采空区覆岩“竖三带”孔隙率三维分布研究

    Study on 3D distribution of porosity of overburden “horizontal three-zones” in goaf

    • 摘要: 煤矿采空区裂隙空间是瓦斯灾害和火灾主要场所,分析其内部气体流动规律首先要得到切合实际的采空区孔隙率。在分析采空区覆岩裂隙场呈“横三区”、“竖三带”的差异性分布特征的基础上,结合“O”型圈理论和岩梁理论,分析并得到采空区垮落带碎胀系数空间分布和断裂带岩层下沉量分布函数;建立了采空区孔隙率三维分布模型,通过实际案例验证模型的适用性,得到垮落带孔隙率为0.1~0.43以及断裂带孔隙率在距底板20~30 m取得最大值0.31。研究结果表明:垮落带内破碎煤岩孔隙率受碎胀系数影响呈“铲”状分布,从压实区沿x轴、y轴、z轴指向垮落带四周边界,其值由最小逐渐增大;断裂带内受规则移动带下沉量及破断岩石长度的影响,离层发育呈四周大中间小,孔隙率分布呈“双驼峰”状,距工作面和煤壁30~50 m的“凸峰”孔隙率大,随埋深变浅,孔隙率最大值向采空区中部靠拢,基本稳定线增大,采动裂隙形态符合“O”形圈分布。

       

      Abstract: Fissure field in goaf of coal mine is the main site of gas disasters and fires. To analyze the inside gas flow law, realistic goaf porosity must be obtained first. Based on the analysis of the different distribution characteristics of “horizontal three zones” and “vertical three zones” of overlying strata fissures in goaf, combined with “O” ring and rock beam theory, caved zone is analyzed and obtained with distribution of bulking factor and distribution function of subsidence of fractured zone, a three-dimensional distribution model of porosity in goaf is established. The applicability of the model is verified through actual cases, and porosity in caved zone is 0.1 to 0.43 and fractured zone is obtained. The porosity reaches the maximum value of 0.31 at a distance of 20 m to 30 m from the bottom plate. The results show that porosity in caved zone is distributed in a “hovel” shape under the influence of bulking factor. From compaction zone along x, y, and z axes to boundary, its value gradually increases from the minimum; in fractured zone, affected by the amount of subsidence in the regular moving zone and the length of the broken rock, the development of the separation layer is large in the surrounding area and small in the middle, and porosity is in a “double hump” shape, and the “bump” is 30 m to 50 m away from the coal face and coal pillar. The porosity is large, as the buried depth becomes shallower, the maximum porosity is closer to the middle in goaf, the basic stability line increases, and the shape of fissures conforms to the distribution of the “O” ring.

       

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