Experimental study on rock's mechanical capabilities under impact loading with confining pressure

In order to investigate rock's dynamic compression capabilities,amphibolites were subjected to impact with different confining pressures(0 ~ 6MPa) and strain rates(50~170s-1) by using the split Hopkinson pressure bar(SHPB) of 100 mm diameter with a confining pressure device and a thin red copper circular plate as pulse shaper.The validity of SHPB experiment was analyzed.Experimental results show that the dynamic compressive strength and specific energy absorption of amphibolites are strain-rate dependent;the strain-rate effect can be expressed with linear approximation;the failure strain of rock increases with the increase of strain-rate,and the dynamic strength increasing factor is approximately linearly related with the logarithm of strain-rate.The strengthening effect and toughening effect become more prominent with the increase of confining pressure in the same range of strain rate.Under confining pressure and dynamic loads,rock takes compression-shearing damage as the principal failure mode.In SHPB experiments,the amphibolites were tested,with the loading time proportion about 69.5% at nearly constant strain rate,which can fulfill the requests of stress equilibrium and the nearly constant strain rate loading.It is demonstrated that the SHPB tests are effective and the results for amphibolites are reliable.