Deformation,Fracture And Acoustic Emission Characteristics' Experimental Study Of The Sandstone Of Rock Painting In Helan Mountains

The Rock Painting in Helan Mountains have been exposed to the natural environment for a long time and rock weathering is becoming more and more serious.They are badly damaged and need to be protected immediately.In this study,the acoustic emission test was conducted in addition to the basic physical and mechanical tests on the sandstone of Helan Mountains.Firstly,the correlation between porosity and bulk density of rock samples was tested.On this basis,using ultrasonic to classify the rock samples.Then Brazilian test direct shear test uniaxial test and triaxial test were carried out.The results show that uniaxial and triaxial tests have obvious compaction stage;the strain-softening stage of triaxial rock samples is not obvious,and they all directly reach to the crack growth phase under residual strength.The softening stage of triaxial rock samples is not obvious,and they all directly reach to the crack growth stage;the peak stress of triaxial compression increases with the increase of confining pressure.Furthermore,acoustic emission tests were carried out simultaneously in the uniaxial and triaxial compression processes.The acoustic emission results of rock samples all have the compaction stage,the rising stage and the peak value.At the initial compaction stage and the elastic stage,the AE rate is very low and reaches its maximum at the peak stress.In the crack growth stage,AE events still exist,but the maximum value is far less than the peak value.The curve of ringing counts follows roughly the same trend as that of the energy curve.Finally,on the basis of accumulated acoustic emission energy,damage variable was built based on Weibull distribution and studied the process of damage process of rock samples in uniaxial and triaxial test.In elastic deformation stage,the damage of rock is almost zero.Once reached the nonlinear deformation stage,the damage increases gradually.When the sample reaches the peak strength,the rock damage increases significantly.The damage curve is consistent with the stress-strain curve,indicating that AE parameters of rocks can accurately represent the damage process of rocks.Through a series of experiments and analysis,it provides theoretical and experimental support for the basic research of Rock Painting in Helan mountains.It will promote the protection of rock paintings and provide a guarantee for the protection of stone cultural relics in China.