A weight combination anisotropic strength criterion considering the effect of joint orientation

In natural geological bodies, many sedimentary or metamorphic rocks exhibit significant bedding or cleavage characteristics. Such rocks show remarkable anisotropy and nonlinearity in mechanical behavior. Therefore, the strength theory of isotropic homogeneous bodies is difficult to meet the design requirements of this type of rock mass engineering. In particular, there are few reports on the research of anisotropic strength criteria under multiaxial stress, which seriously affects the safety of underground rock mass engineering construction and design. The spatial relationship between weak planes and principal stresses is the key to the anisotropy of the mechanical properties of jointed rock masses. In view of this, this paper deduces the strength criterion of layered rock masses under multiaxial stress by analyzing the normal stress and shear stress on the weak planes of joints and combining it with the Mohr–Coulomb strength theory. However, this criterion cannot describe the failure of intact rock matrix materials. To address this limitation, this paper normalizes the influence of joint orientation on strength and constructs a weight combination anisotropic multiaxial strength criterion considering the influence of joint direction. Then, taking the influence of joint direction as a weight parameter and multiplying it by the strength criterion of intact rock, the relationship between the failure strength of layered jointed rocks and joint direction is established. The model was verified by 507 sets of experimental data from nine types of rocks, confirming its good applicability and reliability in describing the influence of joint orientation on rock strength.