Experimental research on effect of loading rate for dynamic fracture toughness of rock

In order to obtain dynamic fracture toughness of rock under high loading rates and to analyze the rate effect,an experimental procedure using edge-notched disc specimen was presented.Split Hopkinson Pressure Bar(SHPB) with a wedge and its holder appended to the end of the incident bar was used to exert dynamic split force at the edge notch of the specimen.The strain gauges were attached near the tip of the notch in order to detect the time of crack initiation;the splitting force history and the time of crack initiation were put into the finite element model to obtain the dynamic fracture toughness at crack initiation.The experimental results indicated that up to loading rate of 18.85×104 MPa.m1/2s-1,the dynamic fracture toughness of marble increased remarkably with the raise of its loading rate,but the increasing trend gradually reduced.There was obvious scattering for the test results of dynamic fracture toughness under high loading rates.