Effect of loading rate on transgranular-intergranular fracture in charcoal gray granite

Willard, R. J.; McWilliams, J.R.

doi:10.1016/0148-9062(69)90042-4

Cited by 8 publications

(3 citation statements)

References 3 publications

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“…ε 2 in Figure 17), which agreed with the findings that were presented in other studies [60][61][62]. Furthermore, considering the evolution of the cracks and the increase in the strength and Young's modulus, the conclusion that the transgranular cracks sustained more energy than the intergranular cracks [54,63] was verified in this study.…”

Section: Comparison Of Stress-strain Curvessupporting

confidence: 91%

“…Figure 16 shows that the energy was be released across the grains in the axial direction of the samples under the dynamic loading rate [54]. When the point of a grain touched another weaker grain, the weaker grain was punctured by the stress at the point of contact, which resulted in transgranular cracks.…”

Section: Crack Evolution Under Different Directions and Strain Ratesmentioning

confidence: 99%

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Microcrack Evolution and Associated Deformation and Strength Properties of Sandstone Samples Subjected to Various Strain Rates

Chen

2018

Minerals

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The evolution of micro-cracks in rocks under different strain rates is of great importance for a better understanding of the mechanical properties of rocks under complex stress states. In the present study, a series of tests were carried out under various strain rates, ranging from creep tests to intermediate strain rate tests, so as to observe the evolution of micro-cracks in rock and to investigate the influence of the strain rate on the deformation and strength properties of rocks. Thin sections from rock samples at pre-and post-failure were compared and analyzed at the microscale using an optical microscope. The results demonstrate that the main crack propagation in the rock is intergranular at a creep strain rate and transgranular at a higher strain rate. However, intergranular cracks appear mainly around the quartz and most of the punctured grains are quartz. Furthermore, the intergranular and transgranular cracks exhibit large differences in the different loading directions. In addition, uniaxial compressive tests were conducted on the unbroken rock samples in the creep tests. A comparison of the stress-strain curves of the creep tests and the intermediate strain rate tests indicate that Young's modulus and the peak strength increase with the strain rate. In addition, more deformation energy is released by the generation of the transgranular cracks than the generation of the intergranular cracks. This study illustrates that the conspicuous crack evolution under different strain rates helps to understand the crack development on a microscale, and explains the relationship between the micro-and macro-behaviors of rock before the collapse under different strain rates.

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Section: Comparison Of Stress-strain Curvessupporting

confidence: 91%

Section: Crack Evolution Under Different Directions and Strain Ratesmentioning

confidence: 99%

Microcrack Evolution and Associated Deformation and Strength Properties of Sandstone Samples Subjected to Various Strain Rates

Chen

2018

Minerals

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“…A detailed discussion of these results is not presented here, but the microscopic fracture morphology is heavily dependent on the sample configuration. An unexpected result was that the fractures were for the most part intragranular, i.e., 60% to 70% of the fracture length broke mineral grains, the remainder of the propagation path being along preexisting grain boundaries [Willard and McWilliams, 1969]. The microscopic fracture morphology could be further classified into either (1) a single, clean fracture surface as observed for the unjacketed and normally pressurized jacketed tests or (2) a separated surface distinguished by numerous small splaying fractures as observed in the rapidly pressurized dry jacketed samples.…”

Section: Fracture Morphologymentioning

confidence: 99%

Diminished pore pressure in low‐porosity crystalline rock under tensional failure: Apparent strengthening by dilatancy

Schmitt¹,

Zoback²

1992

J. Geophys. Res.

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Rupture tests on internally pressurized, thin‐walled hollow cylinders of Westerly granite with impermeable inner membranes suggest that the conventional, or Terzaghi, effective stress law does not describe tensile failure at high internal pressurization rates near 6 MPa/s. Unjacketed and saturated samples, with an initial pore pressure and for which the inner cavity pressure was increased rapidly with respect to the diffusivity, display substantially increased apparent tensile strengths and deformational moduli much higher than similarly configured but more slowly pressurized tests. Alternatively, the properties of completely dry test pieces with no pore pressure show little, if any, dependence on pressurization rate. Further, the behavior of the rapid unjacketed tests was similar to that for completely dry samples. These observations cannot be explained by the predicted undrained response, but they provide indirect evidence for diminished pore pressure effects reminiscent of dilatant hardening observed in compressive failure experiments. Calculated pore pressure diffusion rates support this suggestion as pore pressure perturbations cannot be damped out on the time scale of the rapidly pressurized tests. It is not clear if these effects are produced by elastic microcrack dilatancy, of which the nonlinear stress‐strain curve of granites is symptomatic, or the irreversible production of new porosity as in compressive shear failure tests.

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Experimental investigation of the strain rate effect on crack initiation and crack damage thresholds of hard rock under quasi-static compression

Zhang

et al. 2022

Acta Geotech.

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Effect of loading rate on transgranular-intergranular fracture in charcoal gray granite

Cited by 8 publications

References 3 publications

Microcrack Evolution and Associated Deformation and Strength Properties of Sandstone Samples Subjected to Various Strain Rates

Microcrack Evolution and Associated Deformation and Strength Properties of Sandstone Samples Subjected to Various Strain Rates

Diminished pore pressure in low‐porosity crystalline rock under tensional failure: Apparent strengthening by dilatancy

Experimental investigation of the strain rate effect on crack initiation and crack damage thresholds of hard rock under quasi-static compression

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