Effect of cyclic wetting and drying on the pure mode II fracture toughness of sandstone

•The effects of wetting and drying cycles on rock fracture toughness and crack propagation were investigated using centrally cracked Brazilian disk specimens.•The degree of degradation of KIIC is always larger than that of KIC.•The ratio of KIIC to KIC decreases with increasing number of wetting–drying cycles. The effect of cyclic wetting and drying on the fracture toughness and crack propagation of rock has been studied using centrally cracked Brazilian disk specimens. The results show that the failure characteristics of sandstone change from brittle to ductile at higher wetting–drying cycles. With increase in the wetting–drying cycles both KIIC and KIC decrease, furthermore, the degradation degree of KIIC is always larger than that of KIC. The ratio of KIIC to KIC decreases with increase in the number of wetting–drying cycles. The experimental results and theoretical values of the fracture criterion agree very well with each other.