Study On Damage Law Of Weathering Layer Granite In The Ion-Type Rare Earth Subjected To Impact Loading

Damage evolution of the ion type rare earth weathering layer under impact loading is mainly researched in this paper,the subject comes from National Natural Science Youth Fund Project.Laboratory tests and theoretical analysis are mainly adopt in this thesis.The research works with the nuclear magnetic resonance technology and SHPB experimental device system as in following:(1)The tests of uniaxial compression strength、ultrasonic velocity and NMR pore on the sample is introduced.The analysis of the relationships between the rock velocity and natural pore、the feature of stress-strain curve under the static load and the relationships between the uniaxial compression strength and velocity is also presented.(2)Based on the nuclear magnetic resonance,the measure of weathering layer granite pore structure in the ion-type rare earth mine is given.As a result,the nuclear magnetic resonance T2 distribution of the original rock sample 、 the distribution character of spectrum area 、 porosity and the information of nuclear magnetic resonance imaging are achieved,Which shows the distribution character of the pore structure inside the rock.The results showed that the distribution of natural rock mainly consists of 5 peaks,it is mainly small size pores distribution of the internal pore structure(3)The impact failure test on rock with different original porosity is finished.Compared with the static load,the stress and strain curve under dynamic load is not existence the lower concave part of the compaction process.There is occurrence of multiple damage modes when the rock subjected to impact loading,Such as compressive shear damage,tensile stress damage,etc.The fragmentation degrees is not determined by the sample’s absolute energy absorbed,but is related to the ratio of the absorbed energy to the critical failure energy.(4)Combined with the nuclear magnetic resonance technology and SHPB experimental device system,The study works of damage evolution of weathering layer granite in the ion-type rare earth mine under the stress wave is introduced.The T2 spectrum before and after the impact、porosity、T2 spectrum area、the variation characteristic of nuclear magnetic resonance imaging and the variation of pore structure distribution inside the rock all be achieved.Above-mentioned study indicatethe damage evolution law of the rock under the dynamic loads and provide a new kind of research method to the dynamic damage mechanics of the rock.The results show that the increase of porosity of rock under dynamic loading is mainly derived from the expansion and coalescence of original pores and the Nascent pore,the distribution of each type of pore size under cyclic impact would tend to be more uniform,which indicates that the damage of rock is regular.(5)Based on the nuclear magnetic resonance imaging technology,the analysis of the same rock after the SHPB impact is given.As a result,the rock pore structure distribution picture before and after the impact is obtainted,which directly shows the variation characteristic inside the rock before and after the impact and make the damage evolution law of the rock microstructure under the impact load become visualization.