Abstract: In order to explore the failure process of deep-buried limestone under different confining pressures, limestone samples were taken from the 1104 level of a mine in Huize, Yunnan Province, and subjected to triaxial compression tests under six confining pressure conditions (10, 20, 30, 40, 50 and 60 MPa), with the entire process being monitored synchronously using acoustic emission technology. Analyses were conducted on the stress-strain relationships, ringing counts, cumulative ringing counts, energy counts, cumulative energy counts, and failure modes of the limestone under different confining pressures. The results show that under different confining pressure conditions, the limestone experiences four sequential stages when subjected to axial pressure: elastic deformation, yielding, plastic development, and brittle failure. The AE energy changes and the fluctuations in the ringing count curve resulting from the development of internal fractures in the limestone under different confining pressures exhibit similar patterns, and the peak values of both gradually decrease as the confining pressure increases. The failure mode of the limestone is mainly shear failure. It exhibits 'Y'-shaped cracks when failing at a confining pressure of 10 MPa and 'I'-shaped cracks when failing at other confining pressures. Under high confining pressures, the fragmentation degree of the limestone decreases, the development of secondary cracks slows down, the limestone becomes more resistant to damage, and its compressive strength increases. The integrity of the crushed limestone increases as the confining pressure rises.

Key words: triaxial compression, limestone, acoustic emission, mechanical characteristic, failure mode