Key technology for rapidly drilling large diameter destressing-drillhole in rockburst coal seam

In order to improve the hole forming rate and construction efficiency of large diameter destressing-drillhole in rockburst mine, based on the analysis of the stress characteristics of coal rock in rockburst coal mine, the dynamic instability characteristics of destressing-drillhole and the construction features, the key points for drilling large diameter destressing-drillhole, the efficient discharge of cuttings and fast drilling/lifting were proposed. Combining with the discharge of cuttings method by dual-power, the technology and equipment for rapidly drilling large diameter destressing-drillhole in rockburst coal seam were formed finally after the design and optimization of key equipment, drilling tools, technology and drilling processes. With the equipment based on the ZDY4000LR rig and the technology including water medium and spiral wide wing drilling pipe, the holes were drilled, safely and efficiently. And the method was proved and used at coal mines of Henan Yima and Shaanxi Binchang. The tests show that:the large diameter pressure-relieving borehole could be constructed efficiently and safely, and the efficiency is increased by 48.9% comparing with high and thin helical blade drilling pipe drilling method. The fole-forming rate reached 100%, the method has high application value and popularization significance. And this method can be used for reference in driiling destressing-drillhde in similar coal mines.