Creep Characteristics And Accelerated Failure Process Of Sandstone Under The Action Of Water Content And Loading Stress Level

The microstructure of sandstone itself makes it absorb more water inside it due to rain and running water.The creep characteristics and creep damage of water-bearing sandstone is a core issue for understanding this type of landslide problem and for early warning and prevention.There are many research results on the creep failure of sandstone,but the influence of water content and stress level on its creep performance and failure process is not very clear.Based on this,this paper will conduct detailed experimental research on the water absorption characteristics of sandstone and its creep characteristics under different water content conditions and different loading stress levels,and analyze and describe the critical evolution characteristics of sandstone leading to the failure process.Through the uniaxial compression test of sandstone,the peak strength,deformation failure characteristics and stress-strain curve type of sandstone were tested and analyzed.Based on this,the loading stress level of sandstone creep failure was determined.At the same time,a water immersion test was carried out on sandstone,which showed that the water content of sandstone increased rapidly with the water immersion time at the beginning,and then tended to be flat,and the water content and water immersion time were approximately in a negative exponential relationship.When the water content is low,the peak strength of sandstone decreases faster with the increase of the water content of sandstone.When the water content is high,the peak strength changes slowly.Through the graded loading test of varying graded increments,detailed experimental observations of the sandstone creep failure process under different graded increments have been carried out.The experimental results show that the instantaneous strain and stress level corresponding to each stress loading level of sandstone increase linearly,and the graded increments The larger the value,the smaller the slope of the linear relationship,that is,the slower the instantaneous strain increases with the load stress level.All levels of instantaneous strain,creep strain and steady creep strain rate increase with the increase of stress level.The creep characteristics under different water content and loading stress levels are analyzed,and it is shown that the greater the water content,the greater the slope of the linear relationship between the instantaneous strain and the stress level,that is,the increase of the water content makes the instantaneous strain increase with the loading stress level.Faster.The stable creep strain rate of sandstone with different water content increases exponentially with the loading stress level.At the same time,the creep strain and creep strain rate corresponding to each loading stress level increase monotonously with the increase of water content of sandstone,and the creep failure stress level decreases with the increase of water content.The creep failure of sandstones with different water content shows the three-stage evolution characteristics of deceleration,stability and acceleration.At the same time,the accelerated damage of adjacent damage can be described as the power-law singularity relation of the distance to the damage time,and the critical power-law singularity index is close to-1.By analyzing the three stages of the whole process of creep development,in order to be able to describe the whole process of simulated creep development,stress switches and nonlinear viscoplastic bodies are introduced,and they are combined with basic components to form a nonlinear creep model and give The mathematical expressions are compared with the test results to verify the model.