“三软”煤层工作面煤壁片帮防治试验研究

Experiment on prevention and control of coal wall spalling in three soft coal seam working face

破碎煤岩加固技术是预防“三软”煤层片帮的有效手段。以“三软”煤层工作面安全开采为背景,通过理论分析,力学试验、三维FLAC计算,现场检测等多元方法,研究了工作面片帮机理、破碎煤岩加固室内力学实验与工作面煤壁加固数值模拟及工作面煤壁加固效果评价,确定了改性煤岩加固力学强度及围岩演化规律,并开展了现场注浆加固及注浆参数试验。综合研究表明:煤壁片帮与支承压力、基本顶运动、采高、煤岩裂隙、煤质等因素密切相关,且越靠近顶板的煤壁更容易片帮,进而得出煤壁的最大挠度ωx和最大转角φ_(max);30%的加固材料加固后的煤岩强度分别比原煤岩分别增加了6.4倍和6.6倍,脆性特征明显;注浆间距等距条件下,最佳注浆压力为10 MPa,注浆后,支承压力应力峰值距煤壁的距离缩短了40%,煤壁前方塑性区降低了33.33%;对注浆加固试验结果在片帮严重区域进行应用实施,将30%的加固材料通过10 MPa(气动注浆)压力下注入煤岩后,浆液在煤壁内形成“注浆材料-煤层”组合体,煤壁由松软、破碎变为整体平整状态,浆液最低扩散半径达到了4 m,煤壁平均片帮量保持在0.3 m以内,支架满足初撑力要求,煤壁变形量得到有效控制,稳定性显著增强。

Broken coal and rock reinforcement technology is an effective means to prevent“three soft”coal seams from falling.Based on the background of safe mining in“three soft”coal seam,this paper studies the working face slope mechanism,indoor mechanical experi⁃ment of broken coal rock reinforcement,numerical simulation of working face coal wall reinforcement and evaluation of working face coal wall reinforcement effect through theoretical analysis,mechanical experiment,three-dimensional FLAC calculation and on-site detection,determines the mechanical strength of modified coal rock reinforcement and the evolution law of surrounding rock,and carries out on-site grouting reinforcement and grouting parameter test.The comprehensive research shows that the coal wall spalling is closely related to sup⁃porting pressure,basic roof movement,mining height,coal and rock fissures,coal quality and other factors,and the closer the coal wall is to the roof,the easier it is to spall,and then the _(max)imum deflectionωx and the _(max)imum rotation angleφ_(max) of the coal wall are ob⁃tained.The strength of coal and rock strengthened with 30%reinforcement materials is 6.4 times and 6.6 times higher than that of raw coal,respectively,and the brittleness characteristics are obvious.Under the condition of equidistant grouting spacing,the optimal grouting pressure is 10 MPa.After grouting,the distance between the peak of abutment pressure stress and the coal wall is shortened by 40%,and the plastic zone in front of the coal wall is reduced by 33.33%.The experimental results of grouting reinforcement were applied in areas with serious spalling.After 30%of the reinforcement material was injected into coal under the pressure of 10 MPa(pneumatic grouting),the slurry formed a“grouting material-coal seam”combination in the coal wall,and the coal wall changed from soft and broken to the o⁃verall flat state.The lowest diffusion radius of slurry reached 4 m,and the average spalling amount of coal wall remained within 0.3 m.The support met the initial supporting force requirements,and the coal wall was deformed.