Post-peak Rheology Test And Analysis Of White Sandstone

The excavation of deep underground engineering will lead to a certain extent of fracture zone in the surrounding rock.Due to the difference of rock mineral composition,internal structure and cementation,the rheological properties of different fractured rocks should be different.In view of this,in this paper,uniaxial compression test,triaxial compression test and post-peak rheology test of complete white sandstone samples were carried out by using rrmt-150 c and MTS815 electro-hydraulic servo rock mechanics test system to study the basic mechanical properties of complete white sandstone samples and analyze the post-peak rheology properties of white sandstone under different stress states.Combined with the results of post-peak rheological characteristics of red sandstone studied by our research group,the difference of post-peak rheological characteristics of two kinds of sandstone was compared and analyzed.Based on the results of two kinds of post-peak rheological tests,the determination method of long-term strength behind peak is discussed.The main research results of this paper are as follows:(1)The basic mechanical properties of white sandstone under uniaxial and triaxial compression were obtained through the basic mechanical tests of white sandstone under uniaxial and triaxial compression,the stress-strain curve characteristics,strength and deformation characteristics of white sandstone under different confining pressures were analyzed,and the failure modes of white sandstone under uniaxial and triaxial compression were studied.(2)The influence of initial stress level and confining pressure on post-peak creep was studied by triaxial compression stress relaxation test and post-peak creep test of white sandstone,and the influence of initial confining pressure and confining pressure increment on post-peak creep was analyzed.(3)The difference between post-peak stress relaxation and creep characteristics of the two sandstones and the influence of different conditions on the post-peak rheological characteristics of the two sandstones are analyzed.The results show that the post-peak stress relaxation and post-peak creep characteristics of white sandstone are more obvious,and the change of confining pressure and the application of confining pressure increment have greater influence on the post-peak rheological characteristics of red sandstone.The difference between them may be caused by the different post-peak failure modes.(4)A new method for calculating the long-term strength of rock after peak is proposed and verified.The results show that the post-peak long-term strength values obtained by this method are similar to the post-peak creep characteristics of rocks,indicating that this method is feasible to some extent.The improved western original structure model was used to describe the post-peak creep characteristics of white sandstone and the creep model parameters were determined.