Study On Variation Mechanism Of Wave Velocity And Intensity Of Red Sandstone With Different Water Content

Red sandstone is a kind of common rock,whose property in water strength loss is large,which will lead to poor engineering characteristics,and then will seriously affect the project construction,and even threaten the personal safety of construction personnel.Red sandstone is distributed all over the world,but different geographical environments will lead to different properties of red sandstone in different regions.In order to study variation mechanism of strength and wave velocity of red sandstone under different water content as well as the strength calculation theory,this paper takes the red sandstone in Lanzhou area as the study object,adopts the means of laboratory test and theoretical analysis to deeply study the uniaxial strength characteristics of red sandstone under different water content states and establishes the theoretical model of wave velocity calculation intensity.First,wave velocity test and water absorption test are conducted on the original standard red sandstone samples.It is found that with the gradual increase of water content,wave velocity of red sandstone samples decreases rapidly first and then slowly.Moreover,the different water absorption laws of red sandstone samples with different initial wave velocities are compared horizontally.Then,samples were taken from the same red sandstone rock block to prepare standard red sandstone cylindrical samples,and samples with different water contents were designed by using steam to improve the water content.Uniaxial compression test was conducted,and it was found that the strength characteristics and elastic modulus of the samples decreased exponentially with the water content.After the laboratory test,on the basis of equivalent medium theory and elastic theory,the concept of stress wave is introduced,the rock model under uniaxial condition is established,and the theoretical formula of wave velocity prediction strength is derived,and the influence mechanism of wave velocity and water content on strength is discussed from the macro level.The theoretical results are compared and verified with the laboratory test results,and it is found that the two results are basically consistent.And the theoretical value is smaller than the measured value.Under uniaxial condition,scanning electron microscope test was carried out on the test sample and the SEM image and its porosity were analyzed.It was found that with the increase of water content,the porosity of the red sandstone sample gradually increased and its growth rate first increased and then decreased,and its fractal trend was similar to the porosity trend.At the same time,the influence mechanism of wave velocity and water content on the strength is analyzed at the microstructure level.As a result,the wave velocity and intensity variation law of red sandstone with different water content studied in this thesis,and the calculation formula for calculating the intensity of red sandstone wave velocity under uniaxial condition is derived,which has some reference value for analyzing the nature of red sandstone encountering water and provides an idea for the study of rock intensity calculation.