Analysis Of Multiple Anchoring Schemes For Fractured Rock Mass Based On The Cosserat Theory

Rock mass in geological movement formed a large number of joints, which greatly weakened the mechanical properties of rock mass, leave a hidden risk to engineering construction. Anchor reinforcement is a kind of safe, reliable and economic anchoring technology with small disturbance on original rock. Besides, anchor bolt can improve the integrity of rock mass. The strengthening measure can not only improve the integrity of the rock mass, but also play its self-supporting role. which is the most effective and economical means of supporting excavations in rock. The design theory of bolting is determined by engineering experience. This paper introduced couple stress theory to analysis. The theory on the basis of traditional elasticity theory increased a micro rotation and consequent bending effect of medium deformation characteristics, which explain the phenomena of bending deformation and failure near the crack tip. Using the maximum circumferential tensile stress fracture criterion to analyze, and mechanical parameters can be obtained near the crack tip. The following research work carried out on the basis of previous studies in this paper.(1) Deducing the Cosserat governing equations by the Cosserat theory. Writing Cosserat finite element analysis program theory by Fortran software. The cantilever beam bending problem and stress concentration at a hole are researched to validate the finite element method.(2) The maximum circumferential tensile stress criterion is selected as crack propagation criterion to analyze, get the result of the initial crack propagation condition and direction, the length of crack propagation step. Based on the model, a variety of anchoring methods are analyzed, and got the anchoring effect of different reinforcement position.The results shows that if the material constant L is close to the characteristic size, the scale effect is clearly, and couple-stress must be considered. It is found that couple-stress reduces the initial cracking angle in center 45°-inclined crack. In addition, the effect of multiply anchoring schemes on crack propagation is analyzed. The different anchoring methods on the mechanical parameters of the materials increase was obtained, providing a certain reference value for further study.