Spatial evolution mechanism of coal structure damage and gas permeability under water-based ultrasonic treatment

Abstract

Abstract This study investigates the spatial damage effect of water-based ultrasonic on the structure and permeability of high-grade coal. Herein, anthracite from No.10 coal seam of Bangou Coal Mine in Shanxi Province as the research object, and the following were drawn from the experimental research and the gas seepage simulation: (1) the matrix and minerals attached to the coal surface are shattered by bubbles, and some irregular pores and impact pits appear on the surface of the coal. (2) The internal pore structure of coal can be significantly improved in a relatively short period of time, while the fracture structure requires a longer action time. (3) Some large pores and fractures will achieve breakthroughs from nothing to something, with previously isolated and larger aperture seepage pores and fractures interconnected, forming larger connected pore clusters and fractures over the longer action time. (4) With the prolongation of the action time, the coal permeability shows an order of magnitude increase. The growth rate is fast in the pore-creating stage and the formation stage of connected pore clusters, but it is relatively slower in the pore expansion stage.