Mixed mode I/II brittle fracture evaluation of marble using SCB specimen

Abstract

The failure of cracked rock masses is mainly due to the influence of both opening (mode I) and sliding (mode II) of deformation. In this paper, mixed mode I/II fracture toughness of an Iranian white marble (Harsin marble) was investigated both experimentally and theoretically. Several mixed mode fracture tests were conducted on Harsin marble using cracked semi circular bend (SCB) specimens to obtain the mixed mode fracture resistance envelope in the complete range from pure mode I to pure mode II. However, the experimental results were not consistent with the classical mixed mode brittle fracture criteria. It was demonstrated that the low fracture resistance of the tested rock was mainly due to the influence of large positive T-stresses that exist in the SCB specimen when the specimen is subjected to mixed mode loading. It was also shown that the GMTS criterion which uses three fracture parameters i.e. KI, KII and T can provide significantly better estimates for mixed mode fracture in the Harsin marble when tested by the SCB specimens.