Abstract

A revised model of the hydraulic fracture (HF) formulation [1] that accounts for the hydraulically induced shear stress at the crack faces is discussed. It is shown that, due to the order of the tip singularity of the hydraulic shear stress, this component of the load cannot be omitted in the analysis. The amended crack propagation criterion based on the critical value of the energy release rate is derived. A new parameter, the fluid shear stress intensity factor, is introduced and has proved to play an important role in the HF process. It is also shown that the shear stress induced by viscous fluid at the crack faces influences the crack propagation direction in the mixed mode fracture [2]. Numerical simulations have highlighted advantages of the revised HF model. In particular, the small toughness regime is no longer presents a significant computational challenge. The modified formulation opens new ways not only to analyse the physical phenomenon of HF, but for improving the reliability and efficiency of its numerical simulation as well. [1] Wrobel, M., Mishuris, G., Piccolroaz, A. 2017. Energy release rate in hydraulic fracture: Can we neglect an impact of the hydraulically induced shear stress? International Journal of Engineering Science. 111 pp. 28-51. [2] Perkowska, M., Piccolroaz, A., Wrobel, M., Mishuris, G. 2017. Redirection of a crack driven by viscous fluid. International Journal of Engineering Science 121 pp. 182-193.