Graded Loading And Unloading Constitutive And Energy Evolution Of Rock

The mechanical response of rock in tunnel or roadway surrounding rock is often changed by periodic load in the process of excavation,so the study of rock constitutive model under cyclic loading and unloading plays an important role in the stability of tunnel or roadway surrounding rock.The statistical damage constitution of rock under cyclic load plays a key role in predicting the deformation of surrounding rock,and it can also play a guiding role in the support of surrounding rock.In practical engineering,the stress peak value of periodic load is constantly changing,so the graded loading and unloading constitutive model is more suitable for engineering practice.For the establishment of statistical damage constitution of rock,because the number of cracks in rock obeys Weibull distribution,Griffith criterion holds that the failure of rock is caused by crack propagation.Therefore,based on Griffith criterion and Weibull distribution,a constitutive model which can describe graded loading and unloading rock is established in this paper.Although the graded loading and unloading constitution can describe the mechanical response of rock failure,it is not ideal to reflect the failure nature of rock.By comparing the evolution of uniaxial graded loading and unloading stress-strain curve and uniaxial compression stress-strain curve,it is found that the uniaxial compression stress-strain curve is the outer envelope of uniaxial graded loading and unloading stress-strain curve.At present,the research on energy is all about the elastic performance,plastic performance and hysteretic loop evolution in the process of cyclic loading and unloading,but less on the energy evolution in each stage of uniaxial compression failure.The energy analysis of uniaxial compression process is helpful to explore the proportion and evolution of energy among the compaction stage,elastic stage and plastic stage of rock,as well as the energy storage of rock.In this experiment,the uniaxial graded loading and unloading test and uniaxial compression test are used to analyze the energy evolution law in the process of uniaxial compression.Based on the evolution of elastic properties,plastic energy ratio and stress during uniaxial compression failure,the formulas for calculating the energy storage and elastic energy index of rock burst index are modified.Figure 33 table 5 reference 50...