Boundary element analysis for standard specimen configurations in the ISRM suggested methods for determining fracture toughness of rock

In order to provide an analytical basis for the current “Suggested Methods for Determining the Fracture Toughness of Rock” [1] (referred to hereafter as Suggested Methods) proposed by ISRM, a 3-D boundary element analysis was carried out for standard configurations of two specimen types: chevron bend and short rod. From the results, it is shown that the non-dimensional stress intensity factor described in the Suggested Methods for the chevron bend specimens is approx. 10% greater than that determined in this work. This new calibration constant gives a more realistic fracture toughness for Ogino tuff. Good agreement was obtained with the Suggested Methods for the short rod specimen.