采空区覆岩冒落及孔隙率分布规律研究

发布时间：2018-01-26 00:01

本文关键词： 采空区覆岩冒落孔隙率岩体力学 CDEM软件　出处：《河南理工大学》2015年硕士论文　论文类型：学位论文

【摘要】：采空区是由遗煤与破碎岩石堆积形成的多孔介质区域,其内部气体流场分布主要受采空区孔隙率及渗透率的影响,而孔隙率与渗透率是由采空区覆岩冒落下沉规律决定的。因此,分析采空区覆岩随开采变化的冒落规律及三维空间孔隙率分布规律,对研究采空区流场分布规律有重要指导意义。本文以王庄煤矿井田地质概况为研究背景,结合岩体质量评价方法,得到各岩层的节理间距及岩体力学参数。采用CDEM软件对8101工作面进行数值模拟,确定了采空区“竖三带”的分布范围:采空区冒落带范围为0~23m,裂隙带范围为25~60m,并与经验公式计算和现场高位钻孔考察结果进行对比,结果表明模拟得到的覆岩“竖三带”范围与工程实际接近,验证了节理间距和岩体力学参数确定的合理性。通过建立采空区三维物理模型,模拟三维空间条件下采空区覆岩冒落过程,在模型中沿工作面走向、倾向分别取剖面进行分析:当工作面推进500m时,各岩层下沉量均已基本稳定,岩层下沉量达到最大,随着距工作面和煤壁距离的增加,岩层下沉量越大;靠近工作面及煤壁附近,由于受煤壁支撑的影响,下沉量明显减小;沿采空区竖直方向,岩层从下往上下沉量逐渐减小。结合得到的采空区各岩层下沉量,计算得到采空区孔隙率的表达式,并利用MATLAB软件拟合得出采空区三维空间孔隙率分布图,结果表明:沿采空区走向方向,孔隙率随距工作面距离的增大逐渐变小,最大可达到0.3,当距工作面距离大于100m时,孔隙率基本不再变化;沿采空区竖直方向,孔隙率从下往上逐渐减小,但在远离工作面及煤壁处,冒落带范围孔隙率小于裂隙带孔隙率。将三维空间孔隙率分布导入Fluent软件中,模拟工作面及采空区流场分布规律,得到的上隅角瓦斯浓度和工作面两端压差与实测结果接近,验证了数值模拟得到的三维空间孔隙率分布的合理性,为进一步研究采空区流场分布研究提供了理论依据。
[Abstract]:Goaf is a porous media area formed by the accumulation of residual coal and broken rock. The distribution of gas flow field in goaf is mainly affected by porosity and permeability of goaf. The porosity and permeability are determined by the caving and sinking law of overburden rock in goaf. Therefore, the caving law of overburden rock in goaf with mining variation and the distribution law of porosity in three dimensional space are analyzed. It is of great significance to study the distribution of flow field in goaf. This paper takes the geological survey of Wangzhuang coal mine as the research background and combines with the evaluation method of rock mass quality. The joint spacing and mechanical parameters of rock mass are obtained, and the numerical simulation of 8101 working face is carried out by using CDEM software. The distribution range of "vertical three zones" in goaf is determined: the range of falling zone of goaf is 0 ~ 23m, the range of fracture zone is 2560 m, and the result is compared with the result of empirical formula calculation and field high hole drilling. The results show that the range of vertical three zones obtained by simulation is close to that of engineering practice, which verifies the rationality of the determination of joint spacing and mechanical parameters of rock mass. The three-dimensional physical model of goaf is established. Under the condition of three dimensional space, the overlying rock caving process in goaf is simulated, in the model, along the face direction, the tendency is to take the section separately to carry on the analysis: when the face advances 500m, the rock stratum subsidence quantity has basically stabilized. The amount of rock subsidence reaches the maximum, with the increase of the distance from the face and the coal wall, the more the rock subsidence; Near the face and the coal wall, due to the influence of the coal wall support, the subsidence is obviously reduced; Along the vertical direction of goaf, the subsidence amount of rock layer gradually decreases from the bottom to the top. The expression of porosity of goaf is calculated by combining the subsidence amount of each stratum in goaf. MATLAB software is used to fit the three-dimensional spatial porosity distribution map of goaf. The results show that along the direction of goaf, porosity becomes smaller with the increase of distance from face to face, and the maximum can reach 0.3. When the distance from the working face is more than 100m, the porosity will not change basically. Along the vertical direction of the goaf, the porosity decreases gradually from the bottom to the top, but far away from the face and the coal wall. The porosity of caving zone is smaller than that of fracture zone. The distribution of porosity in 3D space is introduced into Fluent software to simulate the distribution of flow field in face and goaf. The gas concentration in the upper corner and the pressure difference between the two ends of the working face are close to the measured results, which verifies the rationality of the three-dimensional space porosity distribution obtained by the numerical simulation. It provides a theoretical basis for further study on the flow field distribution in goaf.
【学位授予单位】：河南理工大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TD325.3

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