Acousctic Emission Characteristics Study Of Rockburst On Grantic After High Temperarature

To date,as the underground engineering expands continuously into the deeper,the rockburst caused by high temperature is increasing.Rockburst is a dynamic failure phenomenon caused by the excavation in the rock mass at high geo-stress area,which is a serious threat to engineers and construction equipment.Therefore,reasonable prediction to rockburst is a significant for the deep underground rock mass engineering.At present,the acoustic emission signal analysis has become one of the most important way to forecast the rockburst.Therefore,acoustic emission characteristics study of rockburst on granite after high temperature has good engineering significance and academic value for the reasonable prediction of rockburst in deep underground rock mass engineering.In this paper,the acoustic emission system is used to monitor the whole process of rockburst in true-triaxial simulation test on granites treated with different high temperatures of 25?,200?,300?,400?,500?,600?,700? different high temperatures.Through the acoustic emission signal analysis,the difference of acoustic emission signals characteristics of three typical failure including small particle ejection,split into pieces and block ejection during rockburst process are studied.Then,the characteristic evolution law of acoustic emission signal of the rockburst process on granite treated with different high temperatures and the precursor information of rockburst are discussed.Finally,using the acoustic emission characteristics index,the rockburst intensity after different high temperatures is evaluated and its regularity is analyzed.The main research work and conclusions are as follows:(1)Based on Short Time Energy(STE)index,this paper presents a new indicators--Short Time Energy Summation(STES)to evaluate quantitatively the rock brittle failure intensity based on the acoustic emission signal.The study shows that the index is feasible.It can reflect AE total energy in certain duration released during rock brittle failure process,and overcomes the short of Short Time Energy(STE)that can only reflect AE energy in a certain moment.Compared with the traditional absolute energy,the STES is more suitable for the quantitative evaluation of rockburst intensity.(2)The curves of Acoustic emission absolute energy index and TELS index in the process of rockburst along with the temperature show that,the rockburst intensity increases first and then decrease with the increase of temperature.the rockburst intensity is the strongest when the temperature is 300? This conclusion is helpful to prevent and control the rockburst disasters in deep underground engineering under the condition of the high ground temperature and high stress.(3)Three typical failure phenomena,i.e.,small particle ejection,split into pieces and block ejection occur in turn in the rockburst process on granite after different high temperatures.The acoustic emission characteristics of three typical failure phenomena are different.Acoustic emission signal during small particles ejection has a lowest amplitude and a highest major frequency,the voiceprint figure presents obvious rung form,the STE attenuates rapidly,the Short Time Energy Summation(STES)is low;The acoustic emission signal during splitting into pieces has a relatively higher amplitude and major frequency,the voiceprint figure presents vertical lines form,the STE attenuates rapidly,the STES is slightly higher;The acoustic emission signal during block ejection phenomenon has the highest amplitude and lowest major frequency,the voiceprint figure presents disorderly grain morphology,the STE is down with shocks,the TELS is much higher than the former two.These differences can provide a scientific basis for the identification of status in the rockburst inoculation,which is conducive to the effectively forecast rockburst.(4)Overall,the evolution law of AE hits,AE hits' time fractal and absolute energy in the rockburst process of the tested specimen treated with different high temperatures is similar with the normal temperature conditions.However,on the eve of rockburst,the duration of AE hits"quiet period" increases first and then reduce with the increase of temperature.It is noteworthy that there are a "high energy zone" in the AE signal absolute energy logarithmic before the rockburst,which can be seen as precursory information of rockburst.The duration of "high energy zone" increases first and then reduce with the increase of temperature.