我国西部的一些高瓦斯坚硬厚煤层存在着顶煤难以回收的问题，这不仅导致了大量煤炭资源的浪费，而且还为采空区带来了潜在的发火危险。为了解决上述问题，结合定向长钻孔分段压裂技术和脉动水力压裂技术的思路，提出定向长钻孔脉动分段压裂技术，以解决常规水力压裂技术面对的一系列难题。本文以玉华煤矿1417工作面为工程背景，综合运用理论分析、物理实验、现场试验等研究方法，对定向长钻孔脉动分段压裂弱化坚硬顶煤技术进行系统研究。本文主要研究成果如下：

（1）通过理论分析，进行了定向长钻孔脉动分段压裂技术弱化顶煤的理论研究。分析可知，定向长钻孔脉动分段压裂对煤体的改造是多方面相互配合的结果，通过发挥水的辅助软化作用、脉动压力的疲劳损伤作用、水力裂隙的块裂作用、支承压力的破碎共同作用，实现对顶煤的有效控制。

（2）通过现场试验以及室内实验的方法，对煤层起裂压力以及脉动频率作出了研究。起裂压力的研究结果表明，1417工作面煤层常规水力压裂的起裂压力约为19MPa。脉动频率的研究结果表明，脉动压力必须保持在一个足够高的值才能发生疲劳破坏，0.5Hz和1.0Hz下该值分别约为单轴抗压强度的75%、77.5%。此外在足够压力和脉动频次下，0.5Hz和1Hz均能造成达到近似的破坏效果。

（3）提出脉动压裂技术和定向长钻孔分段水力压裂技术互相结合的新思路，结合相关技术的施工工艺，通过理论分析和实验室试验设计了胶囊封隔器器和出水短节，优选脉动注水泵、千米钻机以及其他设备，实现定向长钻孔分段工艺和脉动压裂工艺的有机结合，形成具有可行性的定向长钻孔脉动分段压裂工艺。

（4）基于定向长钻孔脉动分段压裂技术工艺进行了弱化顶煤的现场工业性试验。通过玉华煤矿1417工作面现场情况设计了施工参数，成功进行了5个定向长钻孔30段脉动压裂，有效提升了顶煤回收率和瓦斯抽采效果，验证了定向长钻孔脉动分段水力压裂弱化坚硬顶煤技术，保障了工作面安全和高效生产。

Some high-gas hard and thick coal seams in western China have the problem that top coal is difficult to recover, which not only leads to the waste of a large amount of coal resources, but also brings potential fire hazards to the goaf area. In order to solve the above problems, combined with the ideas of directional long borehole segmented fracturing technology and pulsating hydraulic fracturing technology, the pulsating segmented fracturing technology of directional long borehole is proposed to solve a series of problems faced by conventional hydraulic fracturing technology. Taking the 1417 working face of Yuhua Coal Mine as the engineering background, this paper comprehensively uses theoretical analysis, physical experiments, field experiments and other research methods to systematically study the technology of pulsating segmented fracturing of directional long boreholes to weaken hard top coal. The main research results of this paper are as follows::

(1) Through theoretical analysis, the theoretical research on the weakening of top coal by directional long borehole pulsation segmented fracturing technology was carried out. It can be seen from the analysis that the transformation of coal body by pulsating segmented fracturing of directional long borehole is the result of multi-faceted cooperation, and the effective control of top coal is achieved by giving play to the auxiliary softening effect of water, fatigue damage of pulsating pressure, block cracking of hydraulic fracture and crushing of supporting pressure.

(2) Through field tests and indoor experiments, the cracking pressure and pulsation frequency of coal seam were studied. The research results of the cracking pressure show that the cracking pressure of conventional hydraulic fracturing in the coal seam of 1417 working face is about 19MPa. The results of pulsation frequency show that the pulsation pressure must be maintained at a high enough value to fatigue failure, about 75% and 77.5% of the uniaxial compressive strength at 0.5Hz and 1.0Hz, respectively, and under sufficient pressure and pulsation frequency, 0.5Hz and 1Hz can cause approximate damage effects.

(3) A new idea of combining pulsation fracturing technology and directional long drilling sectional hydraulic fracturing technology was proposed, combined with the construction technology of related technologies, the capsule sealer and outlet short section were designed through theoretical analysis and laboratory experiments, and the pulsating water injection pump, kilometer drilling rig and other equipment were preferred, so as to realize the organic combination of directional long drilling segmentation process and pulsating fracturing process, and form a feasible directional long borehole pulsation segmented fracturing process.

(4) Based on the directional long borehole pulsation segmented fracturing technology, the field industrial test of weakening the top coal was carried out. The construction parameters were designed through the site situation of the 1417 working face of Yuhua Coal Mine, and the pulsation fracturing of 30 sections of five directional long boreholes was successfully carried out, which effectively improved the recovery rate of top coal and the effect of gas extraction, and verified the technology of pulsating sectional hydraulic fracturing of directional long borehole to weaken hard top coal, which ensured the safety and efficient production of the working face.