Analysis Of Mechanical Properties And Acoustic Emission Characteristics Of Different Prefabricated Fractured Rocks

In order to study the mechanical properties and acoustic emission characteristics of rocks with different fractures,this paper uses a variety of methods such as laboratory tests and theoretical analysis.Through the SAEU3H acoustic emission system and the STAC 600-600rock triaxial rheological test system,different complete sandstone surrounding areas Triaxial acoustic emission test under pressure,uniaxial acoustic emission test of double-fractured sandstone with different spacings,uniaxial test of single-fractured sandstone at different positions,and uniaxial test of triaxial and rock-like specimens with triaxial and different inclination angles.The characteristics of acoustic emission signals are systematically studied.The thesis mainly carried out the following research work:(1)According to the triaxial tests under different confining pressures of the complete sandstone,the stress loading time curve and stress-strain curve of the complete sandstone are obtained,and the uniaxial compressive strength,internal friction angle,cohesion and elastic modulus of the complete sandstone are obtained Magnitude.(2)Through uniaxial tests on sandstones with different fractures,the strength characteristics of the rocks under different fractures are obtained.Horizontal double-fractured sandstones with varying intervals gradually decrease their strength within a certain range as the fracture distance increases.Containing horizontal single-fracture specimens with different distances from the end,the strength increases with the distance from the single fracture to the end.Gradually decreases.(3)Obtain a proper cement mortar mix ratio(m_c:m_s:m_w=1:0.75:0.375)through multiple tests,configure a rock-like material with similar strength to sandstone,and measure the type of rock through tests.The internal friction angle of the material is 48°,and the cohesive force is11.2 MPa.Rock-like test specimens containing single fractures with dip angles of 0°,15°,30°,45°,60°,75°,and 90°were prefabricated using rock-like materials,and uniaxial compression tests were performed to obtain different inclination angles.The characteristics of the strength change of the single crack sample,the strength of the test piece containing cracks with different inclination angles(0-90°)showed a trend of first decrease and then increase with the increase of the inclination angle.Different inclination angles have different degrees of influence on the strength of the test specimen.Under the conditions of the same crack depth and width,the strength change of the specimens containing cracks with different inclination angles from 0°to 45°is relatively small,while the strength changes of specimens with cracks with different inclination angles from 45°to 90°are relatively large.(4)Analysis of complete rock samples and rock samples containing cracks.It was found that prefabricated cracks would affect the failure mode of the rock samples.When the complete rock samples were broken,they appeared shear-shaped.The failure was dominated by a major crack.There are few cracks,and the overall degree of fragmentation is small;rock samples containing different fractures appear split when they are broken,and a large number of cracks appear inside and outside the rock sample during failure.The overall degree of fragmentation is large.The ultimate failure of the sample is affected by many cracks result.(5)By analyzing the acoustic emission signals during the test loading rupture process,the characteristics of the acoustic emission signal parameters at each stage of loading were obtained.The test results show that sandstone will generate acoustic emission signals during the test loading process,and the acoustic emission ringing count and energy count will show significant peaks when the rock samples are destroyed.Using these acoustic emission parameter changes,we can infer the internal development of rock failure.