Study On Acoustic Emission Of Rocks Based On Uniaxial Compression

In order to introduce the acoustic emission technique into the civil engineering, theacoustic emission characteristics of rock specimen were analyzed in the unconfinedcompression condition by the laboratory acoustic emission tests. The influence factors ofacoustic emission characteristics were analyzed, in addition, the failure mechanisms anddamage characteristics were discussed.The uniaxial compression tests were executed in the rock specimen of marble,granite and sandstone, and the acoustic emission was monitored by the acoustic emissionapparatus in the failure process. The acoustic emission characteristics of the above rockswere analyzed, and the main influence factors for the acoustic emission characteristics,which were particle size of different rocks, strength, stiffness, joints, etc, were inferredby the comparative analysis. However, the acoustic emission characteristics are affectedby the process of rock specimen preparation and the sampling locations. The test resultsindicate that:(1) the failure mechanism of the rocks are different when the loading modesare different;(2) the rate of change of the acoustic emission is affected by the loadingrate, and the rock damages exacerbate when the loading rates increase;(3) the acousticemissions present quiet before the rock damage, so the characteristic can be utilized toforecast the rock failure in the engineering, and the quiet time is long and obvious if therock strength is high;(4) the acoustic emissions express initial compaction phase, ascentphase, peak phase and reduction phase;(5) the quiet time of acoustic emission energyrate is more obvious than it of acoustic emission rate, so the quiet time of acousticemission energy rate can reflect the rock failure in more reasonable manner, and itprovides rational basis to forecast the disaster in the engineering.Based on the tests and analysis, the characteristics and relations of acoustic emissionparameters were analyzed, and the evolution law of the parameters was summarized.Based on the parameter research, the amount of rock damage and the relationship withacoustic emission were analyzed, in addition, the damage model was established. Thetheoretical stress-strain curve which was fitted by the number of events in the acousticemission, and then the correctness of damage model was verified. Kaiser effect of different rock specimen was analyzed by the cyclic loading. The testresults demonstrate that the damage are divided three phases, including initial phase,stable phase and Instable phase. Cathay effect is obvious and the memory of rocks iscorrect and stable when the stresses between the20%~70%of peak intensity.