Mechanical damage characteristics and constitutive model of coal under ultrasonic cavitation erosion.

This article focuses on the effects of ultrasonic excitation on the mechanical damage characteristics of coal bodies and its implications for enhancing coal seam permeability and coalbed methane (CBM) extraction. Using anthracite coal samples subjected to varying durations of ultrasonic excitation, the study quantitatively analyzes changes in mechanical parameters, acoustic emission signals, and microfracture development, revealing that prolonged ultrasonic treatment induces cavitation effects that weaken coal structure, reduce compressive strength and elasticity, and transform damage modes from brittle to ductile. A mechanical damage constitutive model correlating ultrasonic excitation time with coal degradation is established and validated, showing close agreement with experimental peak stress data. The findings demonstrate that ultrasonic excitation promotes the expansion and connectivity of coal pores and fractures, forming seepage networks that effectively improve coal seam permeability and CBM extraction efficiency.