Experimental Study On Independence Of Kaiser Effect Of Granite

Geotechnical and mining engineering design requires reliable situ stress data. Currently, widely used methods of situ stress measurement are costly, and their accuracy is not high enough. Acoustic emission Kaiser effect method open up a new path for measuring situ stress. Although the basic principle of Kaiser effect is clear, but if use it to measure the situ stress, there are still many questions should be answered. Wherein, direction independence of Kaiser effect, which directly related to the rationality of the method for Kaiser effect measuring situ stress.To study the direction independence of Kaiser effect, Guangdong granite were studied, which used uniaxial preload method and Triaxial preload method. The mainly study include two aspects, if there is direction independence of Kaiser effect under uniaxial preloading, and how confining pressure affect axial Kaiser effect under triaxial preloading. Through experiments I get the following conclusions:(1) For reflecting the change details of acoustic emission data, cumulative ringing-time-stress curves are better than AE counts-time-stress curves, and cumulative energy-time-stress curves are better than cumulative ringing-time-stress curves. (2) In single load tests under uniaxial compression, initial loading stage produces less acoustic emission, until about 60% of breaking stress AE started quickly generate. (3) In fractional cycle loading test under uniaxial compression, test rock samples’Kaiser effect exists about 30% -70% of the failure stress. When the stress level reaches 60% or more of failure stress, AE spurt points which similar to Kaiser spots are observed in the unloading stage. (4) Under uniaxial preloading, when the angle between two loading direction is 90°, direction independence of Kaiser effect existed. There is an angle 0 between 10° and 15°, when the angle between two loading direction less than 0, Kaiser effect do not exists direction independence. When the angle between two loading direction less than 0, Kaiser effect exists direction independence. (5) The essence of Kaiser effect is the memory of rock damage. (6) Under triaxial preloading, although the angle between axial pressure and confining pressure is 90 °, but in the case of both applied, axial Kaiser effect does not have direction independence.