Orthotropic Elastic Model and Its Parameters in Anchored Layered Rock Mass under Varying Incident Angles: Development and Validation

Abstract

Rock bolting is one of the most effective and economical methods for jointed rock mass reinforcement. Therefore, the elastic constitutive relationship in an anchored rock mass, which could well reflect the rules of strength and deformation, should be studied. An orthotropic elastic model, which considered varying anchorage angles (α) and the corresponding mechanical parameters, was investigated based on the theory of mechanics of composite materials. To verify the suitability of the model and the mechanical parameters, a WAW-3,000 kN servo universal hydraulic testing machine was used to undertake a series of uniaxial compression tests on the anchored layered rock specimens. The mechanical parameters of composite specimens, such as elastic modulus (E), Poisson’s ratio (ν), peak strength, and its variation with α were obtained. The results showed that the anchored effect of a bolt on the layered rock mass was very significant and anisotropic, for instance, increments in the elastic parameters in three orthogonal directions were quite different with the increase in α from 0° to 90°, which mainly depended on the relative volume content of the component materials in a certain direction. Comparing the calculated E with the experimental values, the variation rules for the mechanical parameters maintained good consistency, and this proved that the calculated equations in this work were reasonable and had acceptable precision. The spillway slope of a reservoir was simplified and simulated and the optimal α was obtained, which further demonstrated the reasonability and applicability of the proposed model from the viewpoint of engineering practice.