Fig 1.
Four fracture phases and load-displacement curve of granite under 3-p-b tests.
Fig 2.
(a) The specimen size of granite with different notched lengths and (b) stress distribution in the crack tips under 3-p-b test.
Table 1.
Different notched lengths for 3-p-b test.
Fig 3.
(a) Test loading system of granite under 3-p-b test and (b) Peak loads of three kinds of grain sizes under 3-p-b test.
Fig 4.
Different fracture phases of granite under 3-p-b test.
(a) Formation of fictitious crack (b) Instable growth of micro-cracks (c) Macro-crack growth and coalescence.
Fig 5.
Granite acoustic emission of 3-p-b test with different grain sizes.
(a) Fine grain (b) Medium grain (c) Coarse grain.
Fig 6.
Comparison of 3-p-b fracture types in granite with three kinds of grain sizes.
Fig 7.
The strength and fracture toughness asymptotic limits under quasi-static load of 3-p-b test.
Fig 8.
Fractal dimension characterization of granite specimen with three kinds of grain sizes.
(a) Grain size = 3mm (b) Grain size = 2.12mm (c) Grain size = 1.01mm.
Table 2.
Average nominal strength σn for different fictitious crack growth Δafic.
Fig 9.
Linear regression results for determination for tensile strength ft and fracture toughness KIC.
Table 3.
Tensile strength and fracture toughness for different fictitious lengths at peak load.
Fig 10.
(a) Digital image of coarse grain and (b) Simulation model based on digital image of specimen.
Fig 11.
Threshold value (I) change in the scanning line.
Fig 12.
The results contrast between numerical simulation and physical experiments under 3-p-b tests.
Fig 13.
Granites with three kinds of grain sizes processed by digital image.
(a) grain size = 1.01mm (b) grain size = 2.12mm (c) grain size = 3mm.
Fig 14.
The 3-p-b numerical model of three kinds of granite with notched length.
Fig 15.
The grain size distribution of three kinds of granite samples.
Table 4.
Micro-mechanical parameters in RFPA [41].
Fig 16.
Failure process of 3-p-b test (notch length = 1mm) of granite disc with numerical simulation.
(a) 200th load step (b) 348th load step (c) 380th load step (d) 500th load step.
Fig 17.
The relation curve of applied load and loading step under 3-p-b numerical test.
Fig 18.
The values of fictitious crack growth Δafic at the peak load under 3-p-b test.
(a) Fine grain size = 1.01mm (b) Medium grain size = 2.12mm (c) Coarse grain size = 3mm.
Fig 19.
The contrast of the nominal strength σn between numerical tests and model prediction.
Fig 20.
Contrast of the peak load between model prediction and numerical experiments under 3-p-b test.