水平应力对顶板跨落角的影响及应用

为得到水平应力对顶板垮落角的影响,进而确定高位抽采钻孔布孔参数,采用理论分析及相似材料模拟实验的方法进行了研究。首先依据基本顶断裂位置围岩结构力学模型,将顶板岩层假设为梁结构,得到单一岩梁在不同水平应力作用下的断裂线位置变化规律。然后将各岩梁的断裂线位置叠加组合,得到水平应力对垮落角发育的影响。为验证理论分析结果,以水平应力值为影响因素设计了三组不同水平应力值条件下的双向加载相似材料模拟实验,得到了不同水平应力值对应的垮落角。研究结果表明:顶板垮落角由各岩梁断裂线位置决定。地基系数较小时,断裂线与地基初始接触位置距离随水平应力的增加表现为先减小后增加,垮落角变化规律同样为先减小后增加,但减小不明显;当地基系数增加时,随水平应力增加,断裂线与地基初始接触位置的距离减小趋势逐渐消除,仅表现为增加趋势,垮落角变化同样表现为增加趋势。现场应用表明,采用双向加载模型得到的垮落角对钻孔布置参数进行优化,优化后钻场抽采浓度及高浓度抽采时间均得到提高。

Study of the Influence of Horizontal Stress on Roof Caving Angle and its Application

In order to grasp the effect of horizontal stress on roof caving angle,and then to determine hole drilling parameters in high extraction,combined method of theoretical analysis and similar material simulation experiment was adopted.Firstly,based on the mechanical model of surrounding rock structure at the basic roof fracture location,the roof rock stratum was assumed to be a beam structure,and fracture line position variation pattern of single rock beam subjected to different horizontal stress was obtained.Then,the fracture lines of each rock beam were superposed to obtain the influence of horizontal stress on the development of caving angle.In order to verify the theoretical analysis results,taking into account of different horizontal stress values,three groups of biaxial loading similar material simulation experiment were designed.Results show that roof caving angle is determined by fracture line location of each rock beam.When the foundation coefficient is smaller,with the increase of horizontal stress,the distance between foundation initial contact position and fracture line decreases first,and then increases.Caving angle exhibits similar variation trend,but the decrease is not obvious.When the foundation coefficient is larger,with the increase of horizontal stress,above-mentioned distance reduction trend disappears,and only increase trend is observed.Caving angle exhibits similar increasing trend.Field application shows that hole drilling parameters can be optimized based on caving angle from biaxial loading model.After optimization,both the drilling field extraction concentration and high concentration extraction time are improved.