Simulation study on damage characteristics of coal impacted by drilling water jet

Abstract

Drilling water jet permeability enhancement technology is an effective measure to solve the permeability of coal seam. However, the research on the damage characteristics of coal seam drilling under the impact of water jet is still unclear. Aiming at this problem, the nonlinear display dynamics LS-DYNA software is used to simulate the damage and failure process of jet impacting coal seam drilling, and its damage characteristics under different conditions are studied. The results show that the jet velocity has a significant effect on the impact depth of the coal rock drilling. The higher the jet velocity is, the deeper the impact depth is. When the jet and coal parameters are constant, the confining pressure can restrain the coal rock drilling impact range from expanding to the deep. Confining pressure continues to increase, and the inhibitory effect is weakened. At the same time, under the action of confining pressure, the effective stress peak value of coal rock drilling failure increases accordingly; the diameter of water jet is an important factor in determining the damage range of coal rock. At the same time, with the continuous increase of the diameter of the water jet, it becomes larger under the influence of water cushion effect and slows down along the deep expansion trend; the size of the drill hole has a significant impact on the damage and crack growth of the coal rock, and the smaller the diameter of the drill hole is, the larger the range of coal and rock crushing pits, and the crack propagation pattern changes with the increase of drill hole size.

Keywords

• water jet
• coal seam permeability improvement
• coal and rock damage
• failure characteristic
• crack propagation