Fig 1.
Sandstone and true triaxial apparatus: (a) grain structure and (b) mineral composition of sandstone, (c) sizes and structure of specimen, (d) rigid loading type rock true triaxial apparatus and (e) its loading structure, (f) rigid platen and strain measurement, (g) loading path.
Table 1.
Specimen type and stress state setting in each condition (Unit: MPa).
Fig 2.
Technical route of this research.
Fig 3.
Fig 4.
Failure modes of intact rock.
Fig 5.
Failure modes of pre-flawed rock.
Table 2.
Statistic of crack quantity of rock in each condition.
Fig 6.
Comparison of crack quantity between intact and pre-flawed rock.
Fig 7.
Macroscopic pattern and fracture characteristic of splitting crack.
Fig 8.
Mesoscopic fracture characteristics of splitting crack.
Fig 9.
Microscopic characteristics of splitting fracture surface.
Fig 10.
Macroscopic pattern and fracture characteristic of oblique crack.
Fig 11.
Mesoscopic fracture characteristics of oblique crack.
Fig 12.
Microscopic fracture characteristics of oblique crack.
Table 3.
Fracture mechanism and classification.
Fig 13.
Variation trends of quantities of different crack types and proportions of tensile-dominated cracks with σ3 increasing.
Fig 14.
Variation trends of quantities of different crack types and proportion of tensile-dominated cracks with σ2 increasing.
Fig 15.
Comparison of percentage of tensile-dominated cracks between intact and pre-flawed rocks under same stress state.
Fig 16.
Macroscopic and mesoscopic fracture characteristics of the small specimen: (a) macroscopic fracture characteristics, (b) mesoscopic fracture characteristics.
Fig 17.
Spalling fracture of surrounding rock in CJPL-II.