Study On Mechanical Properties And Constitutive Relationship Of Artificially Frozen Sandstone

The mechanical properties of artificially frozen sand rock is an important research topic.In this paper,the combination of experimental and theoretical derivation is used to systematically study the undisturbed sandstone of a mine,which provides a theoretical basis for the design and implementation of construction technology.The uniaxial compressive strength test at-8?,-12? and-15? was carried out using a frozen soil testing machine.The stress-strain curves at different freezing temperatures were obtained and the test results were analyzed.The variation of axial compressive strength increases with decreasing temperature,but the stress-strain curves and uniaxial compressive strength of frozen sandstone under different low temperature conditions have different trends.The trend of increasing ultimate compressive strength of frozen sandstone with temperature decrease is mainly between-8? and-12?,and the effect of temperature on strength between-12? and-15?is second,and the overall modulus of elasticity decreases with temperature.However,it increases continuously,but does not increase linearly.Due to the discreteness of the rock sample,the temperature decreases by the same magnitude,and the elastic modulus increases by different degrees.However,lowering the temperature has a limited increase in the elastic modulus of the rock.A complex exponential nonlinear constitutive model is introduced,and the curve fitting is performed based on the composite exponential nonlinear theory.The parametric equations of the model under different freezing temperatures are obtained.Considering the influence of temperature factors,the composite power exponential nonlinear model is improved,and a new composite exponential stress-strain model related to freezing temperature is proposed.The theoretical curve is compared with the experimental results.It is found that the fitting condition is good and the model is built.Rationality.The creep test of the original frozen sample at-8?,-12?,-15?,the loading coefficient of the test process are respectively,and,among them,the uniaxial compressive strength of the frozen sandstone,under low-level loading conditions The test time is about 8 hours.The test of high-level loading conditions ends with the destruction of the sample,and the time strain curve is drawn after the end of the test.The creep curve is analyzed to obtain the isochronous stress-strain curve,which indicates that the creep under different loading conditions is nonlinear.Based on the Xiyuan constitutive theory of fractional derivative,the computer simulation software is used to calculate and fit the creep curve,and the model parameter solution is obtained.The fitting effect is better,and the correlation coefficient is above 0.9,indicating the fractional derivative Xiyuan model.The creep curve of frozen sandstone can be well described.Figure[86]table[13]reference[80]...