Experimental Study On Creep Characteristics And Variation Law Of Parameters Of Sandstone In Haitangshan Tunnel

As with the increasing depth of underground and tunnel engineering,the rheological problems of rock mass are increasingly serious under the condition of complex geologic environment,which has been bringing unprecedented problems and challenges to the long-term stability and security of rock engineering.Therefore,it is of great theoretical significance and engineering value to make research on rock rheological property and analysis the weakening process of physical and mechanical properties.By adopting the method combined with experimental study and theoretical analysis,creep property of the surrounding rock in Fuxin Haitangshan tunnel was researched by MTS815.02 rock mechanics test system,the strength and deformation characteristics of sandstone under different stress levels were discussed in next,then the change rule of creep parameters with time and stress state was studied,finally the variable parameters creep equation was established.The major research works are as follows:(1)Based on the results of conventional triaxial compression test,the basic mechanics and deformation parameters of sandstone were obtained,then the mechanical characteristics and deformation law under the condition of different confining pressure were analyzed,which can provide scientific evidence for the creep tests in future.(2)By the creep experiment of sandstone in the process of fixing confining-grading increasing axial pressure and fixing axial-grading unloading confining pressure,the creep characteristics of axial,radial and volume and the change of Poisson's ratio were comparatively analyzed,and the long-term strength of sandstone was obtained by analyzing the creep rate and isochronous relationship of stress-strain,then the relationships between instantanuous deformation,creep deformation and stress level were analyzed,through which,the creep properties of sandstone were mastered.(3)Based on the improved Nishihara creep model,the variable parameters creep equation was established which can describe the decay and steady creep stage,and analyzed the variation law of creep parameters in different stress state.The variation of creep parameters could better reflect the deterioration process of decay and steady creep stage of the rock structure.