Experimental Study On The Relationship Between Microstructal Characteristic And Fragment Size Of Rock Under Dynamic Loading

Under the background of mine production blasting,the understanding of the original injury by the blasting designer is limited because of the equipment and production efficiency.So in the blasting design,designers usually estimation the damage of rock through their experience.As a kind of complicated geological product,there are many original cracks(injure)and secondary cracks on the rock.Under blasting load these original load and secondary crack extension development is an important factor which causes rock breaking..A more quantitative and convenient way is needed desperately to described the rock damage because of the designers’ indifference of original damage in rock blasting.The studying on the surface of the rock damage and the researching of the relationship between the broken blocks of rock provides the theory for approximation the rock damage by observing rock surface damage.Through the stem diameter of 50 mm split hopkinson experiment device,from the east anshan iron ore of Granite,Phyllite,Quartzite Red Iron and Magnetite Quartzite rock specimen for impact test.With the aid of Scanning Electron Microscope scanning analysis was carried out on the surface of the specimen,obtained the fractal dimension by the method of box-counting dimension of rock specimen’s crack surface in front of impact.The fractal dimension as a characterization of rock surface damage index,and trying to put forward a rock surface’s damage density index as an analogy with the method to describe the damage of existing.Through the hopkinson impact test data analysis,the action of the mechanical properties of the rock and the characteristics of energy dissipation were obtained.In the process of dynamic load under the same warhead,incident energy and energy absorb of unit volume(比能吸收)increases with the increase of impact velocity,the compressive strength of dynamic enhancement factor has a increase trend with the increase of strain rate.Through the screening experiment data analysis,the characteristic distribution size,uniformity coefficient,and the fractal dimension of fragmentation distribution were obtained.Fragmentation distribution fractal dimension could better characterize the degree of rock fragments.The impact velocity could result an increase in incident energy and dissipated energy,and causing the increase in degree of rock breakage blocks of fractal dimension.Contrast fragmentation distribution fractal dimension and surface damage of the rock fractal dimension,it was found that the both had arelationship of approximate into inverse proportion.And puting forward a factor representing the degree of damage and broken blocks of fractal dimension had a similar correlation.