Experimental study of acoustic emission characteristics of coral skeleton limestone under triaxial compression

Through acoustic emission monitoring tests of coral skeleton limestone under different confining pressures, mechanical properties of coral skeleton limestone under triaxial compression and basic AE characteristics were obtained. The study shows that the strength characteristics of coral skeleton limestone accord with Mohr-Coulomb strength criterion. The macroscopic failure characteristics of coral skeleton limestone under the action of triaxial compression show obvious confining pressure effect. In other words, uniaxial compression is shown as split tension fracture surface; with the increase of confining pressure, the "two-stage stepped" macroscopic fracture gradually turns into a single inclined shear zone. The AE time series evolution law of coral skeleton limestone under the action of triaxial compression is basically consistent with the stress-strain curve characteristics, and there is a good logarithmic function relationship between the cumulative ringing count and the cumulative energy count corresponding to the equivalent failure time and the confining pressure. The cumulative pre-peak ringing and cumulative energy counts show a stable and gentle phenomenon before sigma(od), which is in line with the linear elastic deformation characteristics of the rock, and presents a sharp increase at about 90%, which is the beginning of the rapid and unstable expansion of micro-cracks in the rock. The evolution law of pre-peak energy of coral skeleton limestone under uniaxial compression is basically consistent with the characteristics of stress-strain curve, the pre-peak elastic energy and pre-peak dissipated energy also appear the turning point at about 90%.