Fatigue effects on fracturing resistance of rock

A series of laboratory diametrical compression tests, referred to as indirect tension tests, were performed on Brisbane tuff disc specimens to investigate their mode I fracture toughness response to static and cyclic loading as a function of the applied load. Both the static and cyclic loading tests were carried out on Cracked Chevron Notched Brazilian Disc (CCNBD) rock specimens. In the tests described herein, the reduction in fracture toughness under dynamic cyclic loading was found to be up to 52% of static fracture toughness. The experimental results showed continuous irreversible damage accumulation at the tip of the chevron notched crack in the dynamic cyclic tests, strongly influenced by the loading amplitude. Contrary to the static tests, the cyclic tests produced much more crushed material in front of the tip of the chevron notched crack. It was concluded that cyclic loading causes many micro-cracks, resulting in an extensive Fracture Process Zone (FPZ) in front of pre-existing cracks in rocks