Longhole waterjet rotary cutting for in-seam cross panel methane drainage

In order to improve the efficiency of gas drainage before and during longwall extraction, a waterjet rotary cutting system has been developed for in-seam cross panel methane drainage. The purpose of the water rotary cutting system developed was to create artificial fractures along the gas drainage boreholes. During the design of the system, it was perceived that the nozzle geometry is one of the key factors, affecting cutting capacity. Therefore, we studied the structural and geometric parameters of the nozzle and optimized its performance during laboratory tests and numerical simulation. Underground trials conducted in a coal mine, indicate that production of gas drainage before and after cutting significantly increased by up to three times. The advantages of waterjet assisted gas drainage method has been identified as: 1) increasing gas drainage efficiency, 2) a possible development of a gas drainage fractured network within coal seams associated with panel extraction, and 3) reducing the risk of exceeding gas limits during longwalling.