Quantitative assessment of the effect of in-situ stresses on blast-induced damage to rock.

• Investigate the effects of hydrostatic pressure and anisotropic in-situ stress fields on blast-induced damage to rock. • The image processing technique is employed to quantitatively assess blast-induced damage to rock under different in-situ stress fields. • The mathematical relationship between the damage variable and in-situ stress fields is established. In-situ stress significantly affects rock blast damage but there is a paucity of quantitative assessments of damage evolution in rocks affected by confining pressure. The present paper analyses the effect of envelope pressure on blast-induced rock damage through theoretical analysis and numerical simulations. Damage clouds obtained from numerical simulations are processed using image processing techniques. The concept of the damage variable (η) is proposed to facilitate the presentation of the image processing results. The damage variable is found to be negatively correlated with the hydrostatic pressure (P x) at the same moment, in equiaxial in-situ stress fields. In contrast, in anisotropic in-situ stress fields, η is not negatively correlated with P x due to the presence of hoop tensile stresses in the rock. The mathematical relationship between η and P x in equiaxial and anisotropic stress fields are established. An anisotropic damage variable (η k) is introduced to describe the effect of the anisotropy ratio (K) on rock damage, which is found to increase with increasing values of K. The sharp increase in K equal to 4 and 5 is explained in terms of the state of the rock stress distribution under static loading. This study provides insights into the effect of in situ stress on rock blast damage and presents new approaches for analyzing and presenting the data. [ABSTRACT FROM AUTHOR]