Strength Of Rock-like Materials Research Articles

Elastic Modulus and Strength of Rock-Like Material with Locked-In Stress

Locked-in stress is a special stress objectively existing in the rock which has an important influence on the mechanical properties. However, there were few studies on the locked-in stress in rocks. The locked-in stress was simplified into spherical inclusions of stress. Based on the Eshelby inclusion theory, the influence equation of the locked-in stress on the elastic modulus of the rock is derived. Through experiment, the expression of elastic modulus of rock-like material with locked-in stress based on M-T method is determined. Based on Mohr-Coulomb criterion and effective stress principle, the equations for the influence of locked-in stress on strength of rock-like material under uniaxial and conventional triaxial conditions were deduced. Through experimental verification, an empirical formula for the strength of rock-like material containing locked-in stress is obtained. This article provided a method for further studying of the locked-in stress in rock-like material and has certain reference value.

Crack propagation and coalescence due to dual non-penetrating surface flaws and their effect on the strength of rock-like material

Crack propagation and coalescence due to dual non-penetrating surface flaws and their effect on the strength of rock-like material

Investigation into size and strain rate effects on the strength of rock-like materials

Based on a relaxation model, the relationship between spatial and temporal properties of deformation and fracture of rock-like materials is established, the essence of which lies in the finiteness of crack propagation speed and the complex internal structural hierarchy. There exists one-to-one correlation between characteristic length scale and characteristic strain rate, i.e., in order to fracture a sample of size L or activate structural elements of size L, definite strain rate ε̇L must be applied, below which a sample of size L would not fracture or structural elements of size L would not be activated. From the viewpoint of structural hierarchy, the size effect may be considered as the realization of the structural surface strength of smaller scale structural elements with the decrease of the sample size. The essence of strain rate effect is that because of the finiteness of crack propagation speed, the increase of strain rate activates the deformation and fracture process of smaller scale elements before the complete fracture of the sample. The dynamic strength of material is the realization of size effect on strength at the activated smaller scale level of solid. Based on one-to-one correlation between characteristic scale level and characteristic strain rate, size effect equation is transformed into strain rate effect equation. This investigation examines the size and strain rate effects on strength of rock-like materials, which would give better understanding of dynamic phenomena of deformation and fracture of rock mass, including the Earth's crust.

Strength of rock-like materials

This paper deals with the strength of rock-like materials under triaxial stress conditions. The most common theories of brittle fracture are reviewed. Some methods of triaxial strength determination are described and the results compared. The strength dependence of lateral pressure, pore pressure and size of the test sample is described. Some standard tests are suggested. A method for determining the shear strength at high normal pressure has been used as a measure of the strength of a number of Swedish rocks and ores.