坚硬顶板水射流预制缝槽定向预裂防冲技术试验

A prevention technology of rock burst based on directional presplittingof water jet prefabricated slot in hard roof

我国大部分冲击地压发生与煤层上覆坚硬顶板密切相关,为了提高坚硬顶板预裂卸压效果,提出一种坚硬顶板水射流预制缝槽定向预裂卸压防冲方法。针对砂岩顶板,通过室内高压水射流切割岩石,测定不同水力化参数下岩石破坏深度、宽度以及冲蚀体积等缝槽特征指数值的变化规律,并进行现场试验。结果表明,单因素切缝特征试验时,岩石缝槽的特征指数深度、宽度、冲蚀体积与射流压力、喷嘴直径、重复切割次数呈正相关关系;与喷嘴横移速度呈负相关关系,岩石缝槽的特征指数随着靶距的增加呈现先增加后减小的趋势,切割效率最优靶距在5d处;五因素四水平正交试验时,影响缝槽卸压最优化的5个关键因素主次关系分别为喷嘴移动速度、重复切割次数、射流压力、喷嘴直径以及靶距;基于实验室研究规律,选择参数,对顶板高压水射流割缝进行井下试验研究。对于单轴抗压强度68 MPa顶板岩层,切缝半径相比传统刀具式切缝提高了10倍,并降低了压裂时裂缝起裂压力,顶板岩层水射流预制缝的聚能引导下,单次压裂半径最大可达15 m,防冲卸压效果良好。

Most of rock bursts in China are closely related to the hard roof overlying coal seams.In order to improve the effect of presplitting and pressure relief of the hard roof,a directional presplitting and pressure relief method of water jet prefabricated slot of the hard roof was proposed.Aiming at a sandstone roof,the rock was cut by high pressure water jet in the laboratory,and the characteristic index values of the fracture groove,such as the depth,the width and the erosion volume of the rock under different hydraulic parameters,were measured.The field test was also carried out.The results show that the depth,the width and the erosion volume of rock slot characteristic indexes are positively correlated with the jet pressure,the nozzle diameter and the repeated cutting times,while negatively correlated with the transverse velocity of the nozzle.The characteristic index of the rock slot first increases and then decreases with increasing the target distance,and the optimal target distance is 5d.In the four level orthogonal experiment,five key factors affecting the optimization of pressure relief of the seam slotare the nozzle moving speed,the repeated cutting times,the jet pressure,the nozzle diameter and the targetdistance. Through selecting parameters based on the laboratory research rules,the underground experimentalresearch on high-pressure water jet cutting of a roof was carried out. It is revealed that,for the roof rock with anuniaxial compressive strength of 68 MPa,the cutting radius is 10 times higher than that of the traditional cuttingtool and the fracture initiation pressure is reduced. Under the guidance of the energy accumulation of the roof rockwater jet prefabricated joint,the maximum single fracturing radius can reach 15 m,and the effect of anti-impactand pressure relief is good.