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.