基于CDEM的采空区稳定性及临界顶板厚度分析

Analysis of Stability and Critical Roof Thickness of Goaf Based on CDEM

地下隐伏采空区易导致地表塌陷等问题发生,采空区的顶板稳定性关乎到露天开采的安全,确定采空区临界顶板厚度对采空区安全评价具有重要意义。采空区临界顶板厚度的影响因素复杂,与采空区的几何参数及岩体物理力学参数等多种因素相关。通过量纲分析建立无量纲表达式,得到影响临界顶板厚度的无量纲参数。在此基础上,借助CDEM数值计算方法建立数值模型并进行计算分析。建立了二维采空区数值模型,通过改变采空区的几何参数及岩体物理力学参数,计算采空区顶板的安全系数,研究以上因素对采空区稳定性的影响规律,识别影响顶板安全系数的主要影响因素。建立了采空区二维模型和三维模型的计算模型,得到了无量纲表达式中无量纲临界高度与无量纲强度间的关系,采用指数函数进行拟合得到响应的关系表达式。研究表明:弹性模量、泊松比对临界顶板厚度影响不大,采空区高度对临界顶板厚度无影响;黏聚力对采空区安全系数影响最大,采空区跨度、岩体内摩擦角、岩体密度次之;采空区无量纲高度与无量纲强度之间存在指数衰减关系。

Underground concealed goafs is prone to surface collapse and other problems.The stability of goaf is related to the safety of opencast mining.It is of great significance to the safety assessment of goaf to determine the critical roof thickness of goaf.The critical roof thickness of goaf is associated with multi factors such as the geometric parameters of goaf and the physical and mechanical parameters of rock mass.Through dimensional analysis,a dimensionless expression was established,the dimensionless parameters affecting the critical roof thickness were obtained.Based on this theory,numerical models were established and analyzed by CDEM numerical method.A two-dimensional numerical model of the mining area was established,through changing the geometric parameters of the mining area and the physical and mechanical parameters of the rock mass,calculating the safety coefficient of the roof of the mining area,so as to study the influence law of the above factors on the stability of mining area,and identify the main influencing factors affecting the safety coefficient of the roof.Two-dimensional models and three-dimensional models were established,the relationship between the dimensionless critical height and dimensionless strength in the dimensionless expression was obtained,and the relationship expression of the response was obtained by fitting with exponential function.The study results showed that:elastic modulus and Poisson’s ratio have little effect on critical roof thickness,and the height of the extraction zone has no effect on the critical roof thickness;cohesion has the greatest effect on the safety coefficient of the extraction zone,followed by the span of the extraction zone,the internal friction angle of the rock mass and the density of rock mass;there is an exponential decay relationship between the dimensionless height and the dimensionless strength of goaf.