Abstract
Many numerical methods are carried out to study the nonlinear failure behaviors of the rock; however, the numerical simulation methods for the failed rock are still in the research stage. This paper establishes the damage constitutive equation by combining the bilinear strain softening constitutive model with energy dissipation principles, as well as the energy failure criterion of mesoscopic elements based on the strain energy density theory. When the strain energy stored by an element exceeds a fixed value, the element enters the damage state and the damage degree increases with increasing energy dissipation. Simultaneously, the material properties of the damaged element change until it becomes an element with certain residual strength. As the load increases, the damage degree of an element increases. When the strain energy stored by an element exceeds the established value of the energy criterion, the element is defined to be failed. As the number of failed elements constantly increases, failed elements interconnect and form macrocracks. The rock fracture calculation program on the basis of the preceding algorithm is successfully applied to the fracture simulation process in Brazilian splitting and intermediate crack tensile tests.
Highlights
A s a product of geological movements, the rock is a heterogeneous material with complex mechanical properties
Material failures are mainly caused by irreversible internal energy dissipation; the energy criterion is generally significant for determining the rock failure
The bilinear strain softening constitutive model is adopted by referring to document [13], and the energy criteria for the damage and failure of mesoscopic rock elements according to the strain energy density theory and energy dissipation principle
Summary
A s a product of geological movements, the rock is a heterogeneous material with complex mechanical properties. The application of strain energy density theory [11] can comprehensively consider the preceding problems and take the strain energy density that is the sum of the volume deformation energy density and shape change energy density as the criterion of material failure. The advantage of this theory is that it can be well applied to complex geometry, loading conditions, and development situations of mixed cracks [12]. According to Mohr stress circle theory of space state, the stress components on each surface are substituted into formula (4), in the case of linear elasticity, the general expression of strain energy density equation is as follows:. The damage mode of the material can be evaluated based on the energy change process of the material from one element to another
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