Experimental and numerical analyses of double flawed sandstone with a circular cavity under static-dynamic loads

Abstract

To study the damage deformation and crack evolution of sandstone with combined fractures under static-dynamic loads, in this paper, the rock roadway of a mine of Henan Pingdingshan Tian'an Coal Industry Co., Ltd. was selected. Cyan sandstones specimens from the field were processed into a double flawed cube with a circular cavity (100 mm × 100 mm × 100 mm) specimens. The static-dynamic loads mechanical test system independently developed by Chongqing University was used to conduct the physical tests. The discrete element method (PFC2D) was used for the numerical simulations of static-dynamic loads with intermediate strain rates. The results indicated that with the increase of dip angle, the average strain rate and damage degree of the specimens first increased, then decreased, and finally slightly increased under the same dynamic frequency. They reached the maximum at β = 45 °. Additionally, the degree of damage deformation was reduced, as well as the degree of crack development under the same dip angle, with the increase of dynamic frequency. The specimens finally produced tensile failure and shear failure, mainly tensile failure, and the wing crack was the initial macro-cracks. After we compared the experimental and simulated results between the initiation stress, the peak strain and the crack patterns, it can be stated that the physical tests and the numerical simulations were in good agreement which also proved the effectiveness of the simulation method. Moreover, the damage evolution, the crack initiation angle, the failure forms and other flaw forms (length, width, position) of the specimens were discussed.