Research on key technology of pipe jacking drilling equipment for large-diameter rescue borehole of coal mine

In order to solve the rescue problem of collapsed roadways in coal mines and improve the drilling speed of large-diameter rescue boreholes, the construction method of large-diameter borehole with pipe jacking technology was proposed. Specifically, the collapsed rock mass was crushed and the slag was removed by pushing the connectable pipe joints and cutter heads with the main jacking equipment arranged in the chamber, so as to form a rescue channel composed of jacked pipes at last. A composite cutter head with large opening under the condition of collapsed rock mass was developed, which is composed of 10 cutters, 10 hobs and 2 scrapers, and the opening ratio of the cutter head is 40%, capable of meeting the demand for rapid crushing of large slag. Besides, a drive system of small-diameter pipe jacking rescue equipment and a new slag discharge system integrated with peripheral drive, rock crushing and slag discharging were developed, of which the main structure includes the slag discharge pipe, planetary reducer, big gear, cutter head, motor, etc. Specifically, the cutter head and slag discharge pipe rotate under the drive of motor and the slag discharge pipe is welded with spiral slag discharge bars inside. After the coal and rock are crushed and enter the cutter head, the slag will be continuously discharged by the scraper connected with the slag discharge pipe. The maximum particle size of slag discharged is 300 mm, which could solve the problem of requirements for slag discharge with large flow and particle, as well as the layout of slag discharge system in small space. The experimental environment of the accumulation body of the collapsed roadway has been set up, and the industrial experiment of the pipe jacking rescue equipment in the coal mine has been completed with the jacking distance of 102.5 m and the equivalent daily footage of 43.92 m, thus forming a rescue channel with an inner diameter of 1 575 mm. In addition, the changing trend of the cutter head torque and propulsion force during the pipe jacking process has been measured. The research results are of great significance for improving the technical level of emergency response and rescue equipment in China, and minimizing the casualties and property losses under disastrous conditions.