Cosserat ordinary state-based peridynamic model and numerical simulation of rock fracture

The propagation and coalescence of rock cracks is the direct cause of instability in many geotechnical engi-neering structures. To predict the rock crack propagation trajectory and coalescence mode, an ordinary state-based peridynamic (OS-PD) based on the Cosserat continuum is proposed. Compared with classical OS-PD model considering only pairwise force, the effects of the pairwise moment between two material points is also considered in the proposed Cosserat ordinary state-based peridynamic (COS-PD) model. The rotational stiffness and rotation angle are introduced to characterize the microdeformation and microstructure of rock, and the expression of rotational stiffness coefficient is derived. Three numerical cases are presented to compare the performance of OS-PD model and COS-PD model. The effect of the rotational stiffness on crack growth is investigated. The results show that the rock failure process is accelerated by the introduction of pairwise moment, the crack propagation type and coalescence mode are more inclined to shear failure with the increase of rotation stiffness coefficient. Compared with experimental results, it is found that COS-PD model could extend classical OS-PD model and better capture the evolution process of the rock crack.