Size effects on parameters of cohesive zone model in mode I fracture of limestone

A method was proposed to determine the cohesive zone model parameters by taking the size effects into account. It has been shown in the past that among the cohesive zone model parameters, the fracture energy in rocks can be considerably dependent on the specimen size. To incorporate the size effects in the fracture energy of rocks, the Bazant's size effect law was modified based on the concept of the fracture process zone. For this purpose, the fracture process zone length was considered as a function of the specimen size. The proposed approach was employed for determining the cohesive zone model parameters of limestone. Then, the load-displacement curves predicted by the proposed model were compared with the experimental results reported for limestone. It was found that the proposed approach was able to predict the variation of the fracture energy with respect to the specimen size successfully.