The vast majority of rock masses are often anisotropic due to factors such as layering, unequal in-situ stresses, joint sets, and discontinuities. Meanwhile , given the frequently asymmetric distribution of pores , grain sizes or different mineralogical compounds in different locations, they are often adapt the inhomogeneous and anisotropic conditions of the produced samples. In the first stage of this study, in order to better understand the acidizing, a laboratory test was designed to investigate the effects of various operational parameters such as temperature, injection pressure, type and concentration of acids on the properties such as elastic modulus ( E ), uniaxial compressive strength ( UCS ), variations of porosity and permeability, and rock fracture toughness. The results showed that the use of acid generally causes reduction in E , UCS and toughness and increase in porosity, permeability and deformability. The trend of these variations depends on the acid type and operational parameters and the anisotropy properties will be intensified . Maximum variations due to acidizing indicate 67%, 64% and 55% reduction in E , UCS and fracture toughness, respectively and increase permeability threefold approximately . The results of this study could be applicable to validating constitutive behavior and developing coupling numerical models. In the numerical simulation section, for the first time, it is attempted to predict the SIFs accurately by means of anisotropic crack tip enrichments and development of an interaction integral for inhomogeneous materials with the help of extended finite element method (XFEM). Also, the concept of T -stress was introduced to the formulation of stress crack tip field to develop a new criterion for prediction of crack initiation angle and its trajectory in such materials. To verify the accuracy of the proposed approach, the results are compared with the experimental test results and those reported in the literature. It was found that the ratio of elastic modulus, shear stiffness, and material orientation angle have a significant impact on SIFs. However, the rate of change in material properties was found to have a moderate effect on these factors and a more pronounced effect on the failure force . The results highlight the power of the proposed formulation in the estimation of SIFs and crack propagation path in inhomogeneous anisotropic materials.
