Study On Time Dependent Failure Characteristics Of Granite Rock Burst Under True Triaxial Loading

The construction of tunnel in southwest China has faced many difficulties.The geological conditions in this region are special,and the rock burst phenomenon occurred frequently in the construction process and the safety risk is extremely high.According to rock burst damage time and construction of the relationship between time and space,can be in the same hole punctuated occurred many times in the rock burst phenomenon known as "intermittent" type rock burst,such than the effect of excavation unloading rock burst occurred in the process of instant type single rock burst,the failure process on the time dimension is obvious "lag" phenomenon,This time-dependent damage effect is called "time effect" of rockburst in engineering rock mass.Based on the engineering rock mass type intermittent time effect of rock burst Angle,with the specific design of stress path,based on a true triaxial testing machine,high speed camera and acoustic emission system of all kinds of parameter information,damage to different timeliness and granite under different stress loading rate on mechanical,energy,and macro damage,acoustic characteristics analysis,The time-dependent failure characteristics of intermittent rockburst are preliminarily revealed.The main research contents and results are as follows:(1)The true triaxial testing machine is used to carry out the loading and compression test on granite,and the test results show that granite exhibits different lengths of "time effect" during compression failure.The granite samples are divided into "no obvious time effect","weak time effect" and "strong time effect" by the test results.(2)Based on the parameter information obtained from the true triaxial test system,it is found that under the same stress loading rate,the overall variation trend of strain energy of rock samples with different timeliness is obviously different,and the causes of ejection failure are different.Under different stress loading rates,the failure strength of granite samples with the same time-dependent failure increases with the increase of loading rate,but the overall characteristics of the stress-strain curve and strain energy do not change greatly.(3)based on high-speed camera to capture the airport surface granite stone macro process,the study found that under the same stress loading rate,different aging damage sample airport surface macroscopic ejection failure characteristics,the "strong time effect" sample ejection failure process in a certain time span of vacuum/secondary phenomenon of quiet period,This phenomenon does not appear in the ejection failure process of rock samples with "weak time effect" and "no obvious time effect".(4)Based on the data collected by the acoustic emission system,it is found that,under the same stress loading rate,the internal fracture development of the rock sample with strong time-dependent failure experienced a short stop and recovery process during the load stabilization stage.Under different stress loading rates,AE parameters do not show significant characteristic differences,and in the loading stage,both tensile and shear failure coexist and are dominated by tensile failure.Figure [41] Table [10] Reference [74]...