Numerical determination of strength and deformability of fractured rock mass by FEM modeling

The strength and deformability of fractured rock masses are important factors in the design and construction of civil and mining structures built in or on rock masses. The finite element method (FEM) was applied to study the mechanical behavior of fractured rock masses. A damage-softening statistical constitutive model of intact rock was implemented in FEM code in order to model the strain-softening behavior of rock masses. The FEM model was verified against a theoretical solution and resulted in good agreement. The FEM model was then applied to investigate the progressive failure process, scale effect and anisotropic characteristics of uniaxial compressive strength (UCS), and the deformation modulus of fractured rock masses. The numerical results showed that the representative elementary volume (REV) for strength and deformation modulus is 12 m with an acceptable variation of 10%, and the complete stress–strain curves of models greater than REV size were very similar to each other. A linear relationship was also found between the UCS and the deformation modulus. This result seems to support the idea that a rock mass has a critical strain corresponding to the UCS, regardless of the deformation modulus, scale and direction.