Damage And Deformation Characteristics Of Rock Under Impact Load

Under the frequent disturbance of loads,inner structure of rock materials will generate fragile damage,which is accumulated along the way the material have irreversible damage every time.Therefore,it is of vital necessity to study the dynamic characteristics and cumulative evolution of damage of the rocks under cyclical i MPact loading.In actual work,drilling blast method are often used to excavate and tunnel the rock mass,which not only crack the rocks near the blast area,but also cause frequent disturbance to the rock body around the blast area.In such a condition,to discuss the mechanical characteristics under the situation of the rock being initially damaged is helpful to explore mechanical properties of trends of rocks when disturbed frequently.Firstly,to prepare the gneiss test sample with its size being 50×70mm and the test sample in shape of cylinder with the size being 50×100mm.Then,to test the uniaxial compressive strength of rocks by using RMT-150 B tester.Next,to have a dynamic test with the help of the Hopkinson Bar(SHPB)test device under dynamic and static combination of the sample is performed.Based on the one-dimensional stress wave theory and law of conservation of quantity,the dynamic stress-strain curve of the sample and the relationship between average strain rate and energy absorption efficiency can be obtained through analysis and analysis of the test data.Based on ultrasonic testing,damage law has studied the cumulative change law of gneiss damage during cyclic i MPact.Finally,mechanical characteristics under initial damage after the turbulence of SHPB test device are discussed.Conclusions can be made through study in this paper:(1)Energy absorption efficiency of gneiss test sample lies between20%~40%,and when the efficiency is higher the earlier the peak strain will come,then the earlier the instability and failure will occur.(2)It has a positive correlation between the damage degree of test sample and the absorption energy in cyclical iMPact of test sample.Besides,when the test sample is damaged by the last cyclical i MPact,the absorption energy per unit and the absorption energy efficiency will rocket in number co MPared with former one.(3)Damage variable of test sample will increase slowly influenced by the increase effect time of cyclical i MPact when the iMPact energy is low;when the iMPact energy grows to a certain extent per time,damage variable will increase sharply as the effect time increase.(4)Uniaxial compressive strength of gneiss test sample will be lowed as the increase of damage variable;while as the constantly increase of the initial damage variable,the uniaxial compressive strength of gneiss test sample will not continue to reduce.