Acoustic Emission Characteristics During The Damage And Failure Of Water-bearing Rock

Currently, a large number of domestic and foreign scholars on the acoustic emission technique is applied to the rock damage monitoring conducted extensive research, promotes the development and application of this technology, but it is only a single theory for different types of rock damage, and does not take into account the influence of water on the acoustic emission signal, which is a blind spot of the rock acoustic emission study on the characteristics. As we all know, the nature of rock contains a certain amount of water, the groundwater is an important factor affecting the stability of engineering rock rheology, because of the presence of water, the acoustic emission signal becomes more and more complex, in order to solve this problem,this paper on the basis of acoustic emission experiments of rock damage process acoustic emission. With different water content sample damage process of acoustic emission characteristics was studied, the results are as follows.First of all, the full sample with different moisture content in uniaxial compression test, at the same time using the acoustic emission experiment instrument for monitoring acoustic emission of the whole process of the experiment data and records. For sandstone and granite both rock drying respectively, each choose 3 pieces as sample drying, the rest of the bubble water processing, the different between dry and saturated water content of sample and experiment respectively. Test results show that the drying complete rock acoustic emission events and the loading time has the following several stages:the first stage, the initial stage of experimental AE event numbers of slow growth, acoustic emission events did not change significantly; the second stage, the number of AE events rate increase and tend to be stable, the number of AE events for a linear growth;the third stage, before the end of the experiment,acoustic emission event count rate and number of acoustic emission events instantaneous peak until the end of experiment. Is due to the loading rate selected 20 kn/min, 30 kn/min of the automatic control system, as a result, the relationship between the number of acoustic emission events and stress also follow these three stages. For other water rock, its strength will decrease with the increasing of water content, the number of acoustic emission events also decreases with the increase of water content, the sandstone rock strength is significantly less than the granite, the acoustic emission events is less than the number of granite, but its water content greater than granite, influence of water content on acoustic emission characteristics of granite also to be less than the effect on sandstone. Sandstone failure pattern will be increased with the increase of water content and destroy more completely, but its overall failure pattern remains the same; the damage form of granite has very little to do with moisture content.Secondly, conducted with prefabricated crack of different water content of sandstone, granite uniaxial compression experiments of acoustic emission characteristics. Experimental results show that, with prefabricated crack rock's acoustic emission character and integrity of rock acoustic emission characteristics are similar, but with a prefabricated crack rock acoustic emission events growth inflection point first and second stage by comparison, because of its strength is weak in the intact rock specimens, As a result, the number of acoustic emission events is less than the full sample. With prefabricated crack failure pattern is composed of sandstone samples both ends up and down to the prefabricated crack root each have a crack, its water content, the greater the damage more completely, there will be a crushing part damage. Granite failure pattern and sandstone are similar, but the crack is relatively small, almost no crushing destruction.