Study On Creep Damage Law Of Mudstone Under Cyclic Disturbance And Static Load

When underground engineering excavation,blasting,etc,the rock will be subjected to different forms of disturbance load while being at a stable stress level for a long time.At this time,the small disturbance may produce the physical and mechanical properties of the rock under the long-term static load great impact.Therefore,it is of great significance to study the creep mechanical properties of rocks under static and cyclic disturbance loads.Based on this,this paper uses a combination of experimental research,theoretical analysis and numerical simulation to adopt a self-made rock triaxial compression perturbation creep test bench to carry out axially different disturbance amplitudes and triaxial compression at different disturbance frequencies for Pingdingshan mudstone.Creep test analyzes the influence of different factors on the creep mechanical properties of mudstone from the perspective of creep deformation and failure characteristics.The main work content and research results are as follows:(1)The triaxial compression test of mudstone under different confining pressures is carried out,and the basic mechanical parameters such as peak strength,elastic modulus,poisson's ratio,cohesive force and internal friction angle of mudstone triaxial compression are obtained;The triaxial grading loading creep test of rock under different disturbance amplitudes and different frequencies.By analyzed the creep curves and creep failure morphology,the instantaneous deformation,steady creep rate and accelerated creep of the disturbance amplitude to mudstone creep are found.The influence of holding time is more significant.The disturbance frequency is more sensitive to the change of the creep decay time and the acceleration creep stage to the disturbance frequency.The creep deformation mode of the mudstone under the disturbance action is more complicated,and the tensile damage increases with the disturbance amplitude.The characteristics are more and more obvious.As the disturbance frequency increases,the overall failure mode is tensile-shear composite,but the number of macro-cracks increases.(2)By analyzing the results of the triaxial compression disturbance creep test of mudstone,the damage variables which can represent the changes with time,stress,disturbance amplitude and disturbance frequency are proposed and introduced into the Burgers model and the nonlinear viscoelastic plastic series.In the combined model,the mudstone disturbance creep damage model which can respond to the whole process of creep is constructed.The model selection and model parameter calculation based on improved model least squares method are selected,and the creep parameters under various stress levels are obtained.The influence of axial pressure,time,disturbance amplitude and disturbance frequency on damage variables was analyzed by control variable method.(3)Using the FPC~2DD numerical simulation software,the biaxial compression experiment and the biaxial compression creep test are used to debug the mesoscopic parameters,and the mudstone disturbance creep model is established;the three-axis compression creep under different disturbance amplitudes and different disturbance frequencies is performed.In the variable test,the creep deformation and failure characteristics of mudstone are analyzed from three aspects:indoor test and numerical simulation creep curve comparison,creep failure microcrack expansion mode and microcrack number.The paper has 53 figures,12 tables and 108 references.