Investigation of a Self-Excited Pulsed Water Jet for Rock Cross-Cutting to Uncover Coal

Abstract

Safe production and procedures at the driving face are restricted in mines of southwest China by the long periods required for uncovering coal by rock cross-cuts.A new idea is proposed to solve this problem using self-excited oscillations of pulsed water jets.This is proposed to improve the permeability of the seam and increase the gas desorption rate,which will shorten the cycle of rock cross-cutting and coal uncovering.The properties of a self-excited oscillating pulsed water jet were studied.The hydraulic parameters of the jet and the nozzle structure were optimized by investigating how pump pressure and flow rate effect the depth and width of slotting.Application at the Fengchun coal mine shows that the jet may penetrate 1.5 m or more into the coal seam and that the gas desorption rate increases by 4.4 times.Production efficiency is increased by reducing the number of holes drilled (by 60%) and reducing the construction period for uncovering cross-cut coal by more than 70 days.