A prediction model for the slot depth of high pressure water jet

Abstract

Coal mines in China are characterized by low permeability, and hydraulic slotting is an effective technique to increase the gas permeability of coal. However, the slot depth cannot be accurately determined, which results in the layout parameters of the slotted borehole being empirically designed. In this paper, based on the law of momentum conservation, the velocity distribution law at the cross section of the water jet was derived. Based on the linear relationship between water jet impact power and the erosion volume, the law of pressure attenuation of water jet and Mohr–Coulomb criterion, changes of the slot depth with time and the influence range of water jet slot is confirmed. The maximum slot depth prediction model is also established. The results of field test show that the maximum error between the theoretical calculation value and the measured value is less than 10%, which better validates the prediction model of the slot depth.