地面压裂坚硬顶板对矿山压力显现影响的实验研究

Experimental Study on the Influence of Surface FracturingHard Roof on Strata Behaviours

地面压裂是控制煤矿坚硬顶板减少矿山压力灾害的一种新方法。但该方法的有效性以及地面压裂形成的水压裂缝的产状对矿山压力显现的影响尚待进一步研究论证。通过物理相似模拟实验,在模型中坚硬顶板内分别不预制裂缝、预制水平裂缝和预制垂向裂缝并模拟煤层开采,研究了采动过程中顶板的周期垮落、坚硬顶板的破断和工作面的矿压响应。结果表明:随煤层开采覆岩呈“■”型垮落规律,即先垮落采空区上方A区域,然后沿工作面推进方向垮落与A临近的B区域,再垮落A、B上方的C区域,间隔一定周期B、C区域同时垮落;受水平裂缝影响,顶板周期垮落步距平均缩短23.08%;受垂向裂缝影响平均缩短19.23%;含水平裂缝和垂向裂缝的坚硬顶板均提前破断,平均破断步距缩短10.23%;工作面推进至裂缝影响区时,覆岩作用在开切眼煤壁附近的矿山压力和工作面超前支承压力降低,表明压裂坚硬顶板可降低工作面矿压。研究成果对于揭示覆岩垮落规律、地面压裂控制矿压显现规律和矿山压力灾害防治具有重要意义。

Surface fracturing is a new method to control the hard roof of coal mines and reduce mine pressure disasters.However,the effectiveness of this method and the impact of the occurrence of hydraulic fractures formed by surface fracturing on the mine pressure behavior still need further research and demonstration.Through physical similarity simulation experiments,no prefabricated cracks,prefabricated horizontal cracks,and prefabricated vertical cracks were found in the hard roof of the model,and coal seam mining was simulated to study the periodic collapse of the roof,the breakage of the hard roof,and the mine pressure response of the working face during the mining process.The results show that with the mining of coal seam,the overburden collapses in a“C A\B”pattern,that is,first collapsing area A above the goaf,then collapsing area B adjacent to A along the advancing direction of the working face,and then collapsing the area C above A and B,at a certain interval,areas B and C collapse simultaneously.Affected by horizontal hydraulic cracks,the roofs periodic caving span is shortened by 23.08%on average,and by vertical hydraulic cracks,it is shortened by 19.23%.The hard roofs in the models with horizontal hydraulic cracks and vertical hydraulic cracks are broken in advance,and the average breaking spans are shortened by 10.23%.When the working face is advanced to the hydraulic cracks affected zone,the pressures of the overburden strata acting near the coal wall of the open-off cut and the front abutment pressure of the working face are reduced,indicating that surface fracturing of hard roof can reduce the mining pressure in working face.The research results are of great significance for revealing the laws of overlying rock collapse,controlling the strata behaviours through surface fracturing,and preventing and controlling mine pressure disasters.