Study On Creep Constitutive Model Of Red Sandstone Under Dry And Saturated States

It’s very important theoretical significance and practical value that study rheological mechanical behavior and constitutive model of red sandstone under dry and saturated states,for prediction and effective control of the safety and long-term stability of rock engineering.In this paper,the red sandstone is taken as the research object,then according to experimental phenomenon,combined numerical simulation with fractional theory,it’s established that the creep constitutive model which can characterize the creep characteristics of red sandstone under dry and saturated conditions.Simultaneously the method which combines the particle swarm optimization and the least square method is used to identify and analyze the parameters of the creep constitutive model.Afterwards,the creep constitutive model that is created is added to FLAC^3Dto realization of the secondary of the established model.The research contents and results of this paper are as follows:（1）Carry out a series of tests on red sandstone under dry and saturated states,such as uniaxial compression test,uniaxial creep test.Next,the strength and deformation characteristics of red sandstone is analyzed.It was found that,in the uniaxial compression test,the softening coefficient and basic strength index of samples can quantitatively describe the strength deterioration of samples caused by water.Simultaneously the influence of water on the transverse deformation of samples is more obvious than axial strain,which provides a new perspective for research and analysis of the deformation characteristics of water on red sandstone.In the creep test,it is analyzed that the creep axial deformation produced by samples,the starting time of the third stage of creep and long-term strength.Which all demonstrates that the deterioration performance of water on samples is seriousness.（2）According to the change pattern of creep curve of sample,combined with fractional theory,it is constructed that the creep constitutive model which can characterize the creep whole process of samples under dry and saturated conditions.At the same time,according to the creep test results of samples,the PSO-least squares method is used to identify the relevant parameters of the creep constitutive model established in this paper,and the above process is compiled in the matlab program,thereby forming a specific program for relevant parameters inversion of the creep model created in this paper.It finds that the goodness of fit of creep inversion results at all levels is higher than 0.9,and the fitting effect is better,which also shows the effectiveness of matlab program.Afterwards,the created creep constitutive model is examined by the local and global sensitivity analysis,the results indicate that the sensitivity index of elastic element is the hugest why is that it can directly affect the creep axial strain,while the parameters of Abel element and Kelvin mainly take a part in the shape of creep curve.the parameters of Abel element is dominant parameters among them.（3）The difference scheme of stress increment is obtained by deducing the three-dimensional difference scheme of the newly created creep constitutive model of samples.The FLAC3D600VS2010Addin.msi plug-in in FLAC^3D is used to realize the development of the creep constitutive model in Visual Studio 2010.Subsequently,apply the developed model and the burgers model in FLAC^3D to unit test.the validity of the established creep constitutive model is verified by test results.