Investigating the Deformation Characteristics of Dry Mohr-Coulomb Material during Radial Fluid Injection

Understanding of the deformation behaviour of porous geomaterials during fluid injection has direct relevance in several field applications. Studies exploring the resulting deformation field and instability growth within porous media during fluid injection remains limited. Prior research has focused on utilising steady-state/asymptotic cavity expansion models to study the deformation characteristics, with only a few transient models predicting the time-dependent cavity growth. Increased fluid pressure relative to porous material stiffness enhances fluid-solid coupling, inducing plastic deformations beyond linear poroelasticity. Hence, in this study, a transient cavity expansion model proposed by Kumar et al. (2024a) for dry porous media is used to investigate the poroelastic-plastic deformation characteristics during fluid injection. By introducing a new time dependent parameter known as the permeation coefficient, the model adeptly captures the fluid-induced transient behavior of dry porous media. It employs Mohr-Coulomb theory to represent the constitutive behavior under assumptions of small deformation and zero-far field stress. Further, the sensitivity of solid parameters such as porosity and yield strength are investigated for better understanding. During small deformation conditions, crucial dimensionless model parameters such as n and Y exerted significant control over interface growth. It's noteworthy that the expansion of the cavity radius and the elastic-plastic boundary were governed by the dimensionless constant Y.