Study On Shear Failure And Acoustic Emission Characteristics Of Sandstone Structural Plane Under Different Water-bearing States

The structural plane plays a leading and controlling role in the process of rock instability and fracture.Acoustic emission technology has a great advantage in judging the internal damage of the rock,identifying the failure stage and the precursor information of the damage.Indoor shear tests and acoustic emission tests on rock structural plane can provide a more comprehensive theoretical basis for on-site monitoring of rock stability.In this paper,the research method combining indoor tests and numerical simulation is used to discuss the shear mechanical behavior and acoustic emission characteristics of intact sandstone and sandstone structure plane under different water-bearing stages.The main research contents and achievements are:(1)The direct shear test results show that the existence of the structural plane will weaken the rock shear strength.The larger the first-order undulation angle and normal force,the higher the peak shear strength and residual strength.The direct shear test results show that the existence of the structural plane will weaken the rock shear strength.The greater the first-order undulation angle and normal force,the higher the peak shear strength and residual strength.The peak shear strength decreases with increasing water content.The sample with less water content has larger stress drop and more brittle failure characteristics.Climbing along the first-order undulating body is the internal cause of the dilatation and expansion of the structural plane.(2)Based on the typical failure modes of intact sandstone and sandstone structural plane,the effect of cycle number on peak shear strength and deformation characteristics was researched.Research shows that the change of peak shear strength with the number of cycles is the result of the evolution of"contact effect"and"damage effect".The deformation characteristics during the cycle reflect the volume change of the specimen and the damage accumulation process.The higher the water content,the lower the number of cycles corresponding to strength deterioration and volume compression.(3)By analyzing the changes of the acoustic emission parameters with time during the shearing process,and the relationship between the acoustic emission signal and the shear failure of the sandstone structural plane is discussed.Tests show that the impact count can reflect the acoustic emission activity of the specimen during shearing,while the ring count and energy are more sensitive to damage.Cumulative count curve can characterize the damage accumulation process of sandstone structural plane during shearing process.As the water content increases,the overall level of the acoustic emission signal decreases,the peak value of the acoustic emission parameter is lower,and the cumulative count is less.(4)The law of acoustic emission characteristics during pre-cyclic shearing shows that the load history is an important factor affecting the acoustic emission activity of rocks.Whether it is a intact sandstone or sandstone structural plane,there is an obvious Kaiser effect.As the number of cycles increases,the Felicity effect begins to appear.The sample with high water content has fewer Felicity effects corresponding to fewer cycles.The Felicity ratio can be used to evaluate rock Internal damage.When the Felicity effect occurs during the cycle,the peak impact rate in the direct shear process will increase after the cycle,but the peak ring count rate and energy rate decrease,and the Kaiser effect is the opposite when it is obvious.(5)RFPA^2D can well restore the deformation and failure process of rock slopes with structural plane under load,the simulation results are in good agreement with indoor tests.The number of acoustic emission events is similar to the impact count,and the energy is still more sensitive to damage.The homogeneity has a significant impact on the acoustic emission characteristics,he greater the homogeneity,the greater the number of acoustic emission events and energy peaks,and the more obvious the brittle failure characteristics.