Wave And Resistivity Characteristics Experimantal Research And Damage Evolution Analysis Of Periodic Saturated Sandstone

In the construction of inland river ports,because the water level in the area where the project is located is easily affected by seasonal changes and similar waters,the foundation of the hydraulic structure of the port area is in a dynamic water environment for a long time or intermittently,and the water level of the bedrock is affected by the water level.The cyclical changes affect the bearing rock mass to be in a state of full waterwater loss.Therefore,considering the occurrence environment of engineering rock mass and carrying out the research on the damage evolution law of rock structure under cyclic saturated water has important theoretical significance and engineering practical value.In view of this,this paper relies on the National Natural Science Foundation of China,through the uniaxial compression test,mesostructure scanning electron microscopy test,sonic test and resistivity test of 8 different periodic saturated sandstone specimens,based on the characteristics of wave electrical properties.A method for characterizing the evolution of periodic saturated sandstone damage.The main research contents and results are as follows:(1)After the sandstone was subjected to the dry and saturated water cycle test,the saturated bulk density,saturated water content,void fraction and mass loss rate were all logarithmically increasing with the number of cycles.The first three physical quantities showed a low cycle period(less than 5 cycles).The growth rate is fast and the increase is large.The high cycle period(above 5 cycles)has a slow growth rate and a small increase.The quality loss rate is characterized by small increase in the previous period and slow change,and the increase in the later period is large and the change is fast.(2)The uniaxial compression test of the periodic saturated water sandstone obtained the strength and the average elastic modulus decreased with the logarithm of the number of cycles,which showed a significant decrease in the early stage and a slow decline in the later stage.The electron microscopic scanning test of the sandstone was found.With the increase of the number of cycles,the rupture section of the 200-fold image changes from smooth to rough and fuzzy to the cracks,and the cracks are gradually deepened by the compactly connected mineral particles,less cracks and primary voids under the 500-fold image.Many cracks are accompanied by new cracks and a large number of new void structures.(3)The acoustic wave and resistivity tests were carried out on the sandstone under periodic saturated water.The results show that the wave velocity and attenuation coefficient of the saturated and dry sandstone are exponential and power function respectively,and the velocity is decreasing at low cycle.The amplitude and the amplitude are large,and the speed and the amplitude of the wave velocity decrease are small.The nonlinear coefficient of the saturated state increases logarithmically with the number of cycles,while in the dry state,it exhibits a quadratic function change that increases first and then decreases.The sandstone resistivity in the saturated and dry state increases first and then decreases with the number of cycles,and a sudden change occurs after 13 cycles of the cycle.(4)The correlation between acoustic and resistivity parameters and physical and mechanical parameters of sandstone under periodic saturated water is analyzed.Damage variables based on wave velocity,attenuation coefficient,nonlinear coefficient and resistivity are established,and periodicity is analyzed by using different damage variables.The damage evolution process of sandstone under the action of saturated water shows that the damage sensitivity of different damage variables to sandstone under periodic saturated water is different,which is characterized by nonlinear coefficient > wave velocity > resistivity > attenuation coefficient.