An extended fracture mechanics-based model to simulate underground injection into multilayered rock strata.

• An extended fracture mechanics-based model is proposed to simulate underground injection into multilayered rock strata. • Exact analytical solutions of SIFs and ground deformation for the crack problem are obtained. • Stiffness and stiffness variation pattern of the caprock layers have significant effect on the SIFs and ground deformation. Underground injection of liquid materials is a critical practice in geological engineering with various applications, such as geologic sequestration of carbon dioxide, deep geologic disposal of hazardous waste, and hydraulic fracturing for oil and gas extraction. However, these practices can induce ground heave and alter the stress field in the surrounding geo-medium. Understanding the mechanical behaviour of rock system during the injection is thus important for mitigating underground injection-induced adverse effects. In this paper, we propose a fracture mechanics-based model to simulate the underground injection process in multilayered rock strata. In this model, the injection region is idealized as a penny-shaped crack and injection process is simulated as pressurization of the crack. The crack problem is solved analytically by the General Kelvin's Solution (GKS)-based method for multilayered elasticity and Fredholm integral equation technique. Solutions are given for the key geophysical parameters including mode I/II stress intensity factors (SIFs) and ground displacements. Numerical studies are conducted to explore the role of material inhomogeneity of the multilayered rock strata on the induced ground heave and the SIFs at the crack tip. Our results demonstrate that the shear modulus and position of the hard caprock layer significantly influence ground movements SIFs, offering valuable insights for controlling injection rates and selecting appropriate injection sites. [ABSTRACT FROM AUTHOR]