| Zhejiang is a province with frequent geological hazards.Landslide geological hazards occurfrequently,which brings great harm to the economic construction and people's lives and property of the province.Therefore,the monitoring and early warning work of landslide disasters is extremely important.It is a hot topic in the field of geological hazard prevention and control to develop new monitoring and early warning technology for landslide hazards.Acoustic emission technology can reflect the process of rock fracture,and the information captured can be earlier than the macroscopic performance.In order to apply acoustic emission technology to monitoring and early warning of rock landslides,it is urgent to carry out basic research on the relationship between acoustic emission signal characteristic parameters and rock mechanical properties of different lithologic rocks in the process of failure.Based on the requirement of landslide monitoring and early warning in Zhejiang area,the acoustic emission signal characteristics of basalt in Zhejiang basalt platform area and sandstone,limestone and tuff in Northwest Mountainous Area of Zhejiang province were studied.STYE-3000 E pressure testing machine and WAW-3000 B universal material testing machine are used for uniaxial compression test,shear test and structural plane shear test.DS5-16 B full information acoustic emission signal analyzer was used to monitor the acoustic emission information in the whole process of the test.During the uniaxial compression experiment,the CASI-RTY digital network transmitter is used to monitor the infrasound information.At the end of the test,the acoustic emission and infrasound signal will be processed and analyzed.The main conclusions are as follows:(1)Under uniaxial compression loading conditions,the generation and expansion of internal cracks in rock sample under stress until the rock sample breaks will cause the change of acoustic emission characteristic parameters.The curve of acoustic emission cumulative ringing count and the curve of acoustic emissioncumulative energy will rise from flat to fast until the rock sample breaks is in a straight line during the process of crack expansion and formation of new cracks in rock sample under stress until the rock sample breaks through the crack.(2)Under shear loading and structural plane shear loading conditions,the curve of acoustic emission cumulative ringing count and the curve of acoustic emissioncumulative energy first grow from steady and slow growth to rapid growth until reaching the peak moment of displacement.Thecurves gradually flattened again.After reaching the peak stress,the two statistical curves gradually become flat.The characteristics of two acoustic emission characteristic value curves of rock failure and shear slip process can be used in the monitoring and warning of landslide site.Acoustic emission begins to appear after rock samples are subjected to a certain shear stress by controlling the uniform growth of shear displacement.The curve of cumulative ringing count and the curve of cumulative energy showed obvious correlation with the stress curve.As the stress increases,it rises.Before reaching the peak stress,the change of acoustic emission eigenvalue growth rate and stress growth rate is similar,from slow to fast.(3)Under uniaxial compressive loading,shear loading and structural plane shear loading,the overall variation law of acoustic emission cumulative ringing count and cumulative energy statistical curve of basalt is consistent with other rocks,but progressive failure is obvious before peak stress is reached,and the two curves show the characteristics of step-by-step progressive rise,which can provide a certain amount of experimental data support for monitoring and early warning of rock landslides in Zhejiang basalt platform area by acoustic emission technology.(4)Under uniaxial compression loading conditions,the infrasonic background signal waveform collected in the laboratory is stable,and the overall value is not higher than 0.06.The time-frequency diagram of the bottom signal is stable and the signal strength is not higher than 35.In the process of loading,the amplitude of infrasound signal waveform is small,while that of near-rupture is large.The characteristic frequency of rock fracture of the four lithologies in Zhejiang province is concentrated in 1~6Hz,and has no obvious relationship with lithology. |
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