CHARACTERISTICS OF STRENGTH AND ACOUSTIC EMISSION OF GRANITE AND MARBLE UNDER UNIAXIAL COMPRESSION

Brittleness has an important influence on rock failure mechanism and acoustic emission characteristics. Uniaxial compression and acoustic emission tests were carried out using two different lithological rocks of granite and marble. The strength and deformation characteristics of the two rocks were obtained, and the brittleness was quantitatively evaluated. The evolution characteristics of acoustic emission(AE)energy of two rocks during uniaxial compression were analyzed. Combined with the calculation results of AE b value and their physical meanings, the differences of two rock failure mechanisms were compared. The results are summarized as follows. (1)The ratio of σ_cd/σ_p of the granite used in the experiment is between 0.676~0.745, with an average of 0.706, while that of the marble is in the range of 0.439 to 0.615, with an average value of 0.52. (2)Based on the brittleness evaluation index, combined with the macroscopic failure phenomenon and morphology of the sample, the granite used in this test is more brittle than the marble. (3)In the case of the same axial compression deformation generated during the crack unstable propagation stage, the greater the brittleness of the rock, the larger the amount of circumferential deformation. (4)The high-brittle granite exhibits sustained high-level acoustic emission signals during the crack unstable propagation stage, whereas the weak brittle marble shows a continuously decreasing trend. After the peak strength, the AE signal with high-value energy is more active for the weak brittle marble. (5)The ratio of macro-crack to micro-crack is larger for granite than that of marble during the destruction process under uniaxial compression.