Investigations on the macro‐meso mechanical properties and energy dissipation mechanism of granite shear fracture under dynamic disturbance

Abstract

To explore the mechanical characteristics and failure mechanisms of rock shear fracture under dynamic disturbance, the laboratory shear test and numerical simulation based on particle flow code (PFC) were carried out, and the mesoscopic degradation characteristics and energy dissipation mechanisms of rock shear fracture were analyzed. The results show that: (1) The crack initiation stress of rock under the disturbance condition is relatively reduced by 20%–29%, and there is a “shear fracture weakening effect.” The frequent alternating effect of stress concentration and release at the post‐peak failure stage is more obvious. (2) The number of cracks in rock under shear action shows the evolution of “calm → low speed growth → rapid increase → decrease of amplification → stabilization” with the increase of shear displacement. Compared with the conventional shear test, more cracks, and wider debris zones are formed. The number of cracks increases by 53%–106%, and the number of debris increases by 31%–138%. (3) The energy change trend of disturbance shear fracture test is basically consistent with that of conventional shear test. With the increase of normal stress, the input energy, elastic strain energy and dissipation energy of rock failure point show a certain linear growth feature. Compared with the conventional shear test, the input energy and stored strain energy of the failure point in the disturbance shear test are smaller, with relative reduction of 16.5% and 22.1%. Namely, the normal frequent disturbance reduces the energy storage capacity and failure resistance of rock.

Rock crack initiation triggered by energy digestion

“…Further, the damage evolution can be characterized by elastic bulk modulus and plastic strain energy release rate 19 – 21 . A large number of laboratory experiments and theoretical analyses have confirmed the intrinsic relationship between strain energy dissipation and release in the process of rock deformation and failure 20 , 22 – 25 . Based on the above findings, the stress–strain curve of hysteresis loops obtained by uniaxial compression has been used to characterize the strain energy.…”

Rock Crack Initiation Triggered by Energy Digestion

“…Further, the damage evolution can be characterized by elastic bulk modulus and plastic strain energy release rate [19][20][21]. A large number of laboratory experiments and theoretical analyses have con rmed the intrinsic relationship between strain energy dissipation and release in the process of rock deformation and failure [20,[22][23][24][25]. Based on the above ndings, the stress-strain curve of hysteresis loops obtained by uniaxial compression has been used to characterize the strain energy.…”

Fracture evolution characteristics of strainburst under different gradient stress

“…When rockburst occurs, the elastic strain energy stored in the rock mass is suddenly released, resulting in bursting, loosening, debris ejection and even rock block throwing, which poses a serious threat to the safety of equipment and construction personnel 3 . Therefore, the research on the mechanism of rockburst and its prediction is of great theoretical significance and civil value 4 …”