Study On Dynamic Mechanical Properties Of High Geostress Hard Rock Impact

The course of underground mining is a process from top to the bottom,and the mining face has been falling off gradually with the decreasing of mineral resources which increased the mining depth when the depth reached a certain level the pit would got into deep mining.Before excavating the deep rock mass has been in high stress field,high ground stress could easily deform the deep mine roadway disturb the pillar and cause rock burst.And the rock would be changed in high stress,it is very different from the shallow rock.Blasting plays a vital role in the hard rock mining course,during the mining course the explosive explosion would cause strain rate,which range from 10-s-1 to 103s-1,to the surrounding rock,therefore,it is important to study the dynamic mechanical properties of rock under the high strain rate and high stress.The Sizishan Copper Mine of Yuxi Mining Co.Ltd has expanded to eighteenth mid piece that means it has reached the deep mining areas,this paper focused on the subject of "The Experimental Study On The Dynamic Mechanical Properties of Deep Ores and Rocks" which is a sub-subject of "The Research and Application of Deep Mining Technology of Sizishan Mine",After reading a large number of documents,we analyzed it theoretically,took samples in the field,tested it in the laboratory and finally we systematically studied the dynamic mechanical properties of the deep rock in the Sizishan Copper mine.The main contents and conclusions are as follows:(1)The rock in the SHPB test showed a strong brittleness,the range of strain,strain rate and average strain rate of test-piece was relatively small,while they showed a high dynamic strength and dynamic elastic modulus.Though they were given a high live load,we still was not obtained a high strain rate.The test results showed that the strain of most test-piece was less than 0.008,the average strain rate was less than 70s-1,while the maximum dynamic elastic modulus was more than 140GPa.(2)The heterogeneity of sampled dolomite was very poor,but there was a strong positive correlation between the dynamic strength and the average strain rate;At the test of one-dimensional and three-dimensional static and dynamical combination(12MPa confining pressure),the dynamic strength of the test-piece(under the same or similar strain rate)increased with the increases of axial pressure first,and then it appeared a decreased trend and near the point of 24MPa axial dynamic strength it reached the maximum value.The mechanical properties of test-piece were affected by confining pressure,at the test when we fixed the axle pressure at 24MPa,the confining pressure at 4MPa,it was same with the state of no confining pressure,but when the confining pressure was at 8MPa and 12MPa the dynamic strength enhanced greatly.(3)The axial pressure and confining pressure in a certain range make the test-pieces store strain energy and enhance its impact resistance,it is not conducive to the test-pieces to absorb the impact energy.Although the test-pieces were damaged,the whole may release the energy,and the released large energy could be dissipated in other forms.However,with the increase of impact load,the impact energy of the broken specimen would be gradually larger than the energy released by itself.