During the construction and operation of gas storage reservoirs, changes in the principal stress direction can induce fracture propagation under conditions of lower differential stress, potentially leading to failure in the surrounding rock. However, the weakening of strength due to pure stress rotation has not yet been investigated. Based on fracture mechanics, an enhanced Mohr-Coulomb strength criterion considering stress rotation is proposed and verified with experimental and numerical simulations. The micro-damage state and the evolution of the rock under the pure stress-rotation condition are analyzed. The findings indicate that differential stress exceeding the crack initiation stress is a prerequisite for stress rotation to promote the development of rock damage. As the differential stress increases, stress rotation is more likely to induce rock damage, leading to a transition from brittle to plastic failure, characterized by wider fractures and a more complex fracture network. Overall, a negative exponential relationship exists between the stress rotation angle required for rock failure and the differential stress. The feasibility of applying the enhanced criterion to practical engineering is discussed using monitoring data obtained from a mine-by tunnel. This study introduces new concepts for understanding the damage evolution of the surrounding rock under complex stress paths and offers a new theoretical basis for predicting the damage of gas storage reservoirs. (c) 2024 Institute of Rock and Soil Mechanics, Chinese Academy of Sciences. Production and hosting by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/ by/4.0/).

The matrix has a great influence on the mechanical and failure characteristics of the miscellaneous fill. Based on the laboratory medium-sized triaxial test, the confining pressure tests of 100, 200, and 400 kPa were carried out on the miscellaneous fill under three kinds of matrix with block stone content of 30 %, and the influence of the matrix on the mechanical properties of miscellaneous fill was analyzed. A biaxial test with a confining pressure of 200 kPa was carried out on three kinds of matrix miscellaneous fill samples using the particle flow method, and the influence of miscellaneous fill on the failure characteristics was studied. The test results show that the relation curve of the miscellaneous fill (61-63)similar to epsilon a can be considered as a hyperbola. The miscellaneous fill whose matrix is clay and silty soil always shows shear shrinkage. When the confining pressure is 100 kPa, the miscellaneous fill in the sandy soil matrix shows the property of shrinkage first and then dilatancy. When the confining pressure is 200 kPa and 400 kPa, it shows shear shrinkage. Through numerical simulation, it is found that when the matrix is clay, the shear zone is obvious and the shear failure surface is stable. When the matrix is silty soil, the contact cracks become thinner and the shear bands increase. When the matrix is sandy soil, compared with clay matrix, the overall crack is finer and the shear fracture surface is irregularly distributed.