Study On Rock Mechanics Characteristics And Law Of Cumulative Damage Under Step Impact Loading

This paper is based on the National Natural Science Foundation of China "Study on the cumulative damage evolution and vibration effect of rock mass under the action of frequent blasting loading(E51464015)",aimed at producing blasting damage of this issue to study on the surrounding rock,mainly by the experiment system of SHPB and RSM-SY5 wave tester,RMT-150 C test system,the acoustic test before and after cyclic impact test and uniaxial compressive test,impact loading of rock under impact loading the rock made analysis in mechanical properties under static load and dynamic load,and to define the damage parameters describing the wave velocity method cumulative damage rule of step loading under impact loading,the main research contents and results are as follows:(1)According to the Huygens principle and analysis of the acoustic wave velocity changes to describe the change of micro crack cycle before and after the impact of rock is feasible on the basis of previous studies,the physical and mechanical properties of rock test,briefly introduces the detection technology of nuclear magnetic resonance and sound waves,and the acoustic wave velocity decreases with the increase in porosity.(2)Using the RMT-150 C experimental system of rock uniaxial static compression test,the test results based on the compressive strength and elastic modulus of rocks are accompanied by the increase of porosity decreases with increasing velocity.(3)The use of SHPB experimental system to the conventional rock impact test,the test results based on specimen peak stress with the average strain rate increases with the increase of impact times increased,showing a trend of first increase and then decrease with the increase of impact times;the peak strain has two trends: the first decrease continued to increase.All the specimens increases again,the last time the impact of the dynamic peak strain in the specimen initial impact has increased;the elastic modulus increases with the number of the impact will also have two trends: gradually decreases,the first increases and then decreases;the critical impulse is in the bullet impact velocity 10.5m/s(80J,incident)a critical failure mode of tensile failure,bullet impact velocity(incident energy is larger,namely)the higher strain rate,the rock fragmentation process will absorb more energy,so broken The split surface is more abundant,and the fragmentation of the block is smaller.(4)Cyclic impact test two different loading mode,the specimen can withstand the impact of the number of incident impulse decreases with the level of increase in impulse test is large,about the elastic modulus,peak stress were associated with the increase of impact times decreased significantly;the specimen group loading cycle impact in the experiment,with the increase of impact load,the peak stress of the specimen,the peak strain increases,the elastic modulus increased first and then decreased;the specimen specific energy absorption value increased with cumulative impact times increased.(5)The damage variable is defined by the wave velocity method.It is found that rock is not affected by low impulse load.It will cause damage only when reaching the threshold value.With the increase of impulse and impact times,the rock damage presents an irreversible nonlinear accumulation.