Fractal Dimension of Fracture Surface in Rock Material after High Temperature

Zhang, Z. Z.

doi:10.1155/2015/468370

Cited by 14 publications

(10 citation statements)

References 4 publications

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“…The failure mode changes from brittle to quasi-brittle [95]. More noticeably, another change at around 800 • C is a significant increase in peak strain and shear-slip strain (Figures 13 and 15), indicating that the rock has undergone a certain brittle-plastic transition, which can be verified by the SEM tests [93]. Figure 19 shows the SEM images of fracture surfaces of granite specimens under different heating temperatures.…”

Section: Discussionmentioning

confidence: 57%

Mineral Composition, Pore Structure, and Mechanical Characteristics of Pyroxene Granite Exposed to Heat Treatments

et al. 2019

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In deep geoengineering, including geothermal development, deep mining, and nuclear waste geological disposal, high temperature significantly affects the mineral properties of rocks, thereby changing their porous and mechanical characteristics. This paper experimentally studied the changes in mineral composition, pore structure, and mechanical characteristics of pyroxene granite heated to high temperature (from 25 °C to 1200 °C). The results concluded that (1) the high-temperature effect can be roughly identified as three stages: 25–500 °C, 500–800 °C, 800–1200 °C. (2) Below 500 °C, the maximum diffracted intensities of the essential minerals are comparatively stable and the porous and mechanical characteristics of granite samples change slightly, mainly due to mineral dehydration and uncoordinated thermal expansion; additionally, the failure mechanism of granite is brittle. (3) In 500–800 °C, the diffraction angles of the minerals become wider, pyroxene and quartz undergo phase transitions, and the difference in thermal expansion among minerals reaches a peak; the rock porosity increases rapidly by 1.95 times, and the newly created pores caused by high heat treatment are mainly medium ones with radii between 1 μm and 10 μm; the P-wave velocity and the elastic modulus decrease by 62.5% and 34.6%, respectively, and the peak strain increases greatly by 105.7%, indicating the failure mode changes from brittle to quasi-brittle. (4) In 800–1200 °C, illite and quartz react chemically to produce mullite and the crystal state of the minerals deteriorate dramatically; the porous and mechanical parameters of granite samples all change significantly and the P-wave, the uniaxial compressive strength (UCS), and the elastic modulus decrease by 81.30%, 81.20%, and 92.52%, while the rock porosity and the shear-slip strain increase by 4.10 times and 11.37 times, respectively; the failure mechanism of granite samples transforms from quasi-brittle to plastic, which also was confirmed with scanning electron microscopy (SEM).

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Section: Discussionmentioning

confidence: 57%

Mineral Composition, Pore Structure, and Mechanical Characteristics of Pyroxene Granite Exposed to Heat Treatments

et al. 2019

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“…Mandelbrot et al [42] have shown that fractured surfaces are fractal. Zhang [44] reported a quadratic polynomial relationship between the rock burst tendency and fractal dimension of fracture surface. A fractal dimension threshold ofd f was found, and there was a positive correlativity between the rock burst tendency index and the fractal dimension when d f ≤d f , an inverse correlativity when d f ≤d f .…”

Section: Fractal Structurementioning

confidence: 99%

Fractal Geometry and Porosity

Agboola¹,

Onyango²,

Popoola³

et al. 2017

Fractal Analysis - Applications in Physics, Engineering and Technology

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A fractal is an object or a structure that is self-similar in all length scales. Fractal geometry is an excellent mathematical tool used in the study of irregular geometric objects. The concept of the fractal dimension, D, as a measure of complexity is defined. The concept of fractal geometry is closely linked to scale invariance, and it provides a framework for the analysis of natural phenomena in various scientific and engineering domains. The relevance of the power law scaling relationships is discussed. Fractal characteristics of porous media and the characteristic method of the porous media are also discussed. Different methods of analysis on the permeability of porous media are discussed in this chapter.

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“…Zhang et al [18] conducted statistical analysis of rock fragments under uniaxial compression of various temperature effect; it showed that FD of limestone decreased with temperature, which was a proper characteristic statistic that reflected the degree of fragmentation of limestone after high temperature. Zhang et al [19,20] calculated the correlation fractal dimensions (CFDs) of AE counts series at different stress level using Grassberger-Procaccia algorithm; as the heat temperature rises, the maximum CFD value and the corresponding stress level both increase from 25 ∘ C to 200 ∘ C and decrease from 200 ∘ C to 800 ∘ C and then increase again from 800 ∘ C to 1200 ∘ C; the CFD value at the failure point shows polynomial decline with rising heat temperature.…”

Section: Advances In Materials Science and Engineeringmentioning

confidence: 99%

Fractal Characteristics of Rock Fracture Surface under Triaxial Compression after High Temperature

Zhang

2016

Advances in Materials Science and Engineering

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Scanning Electron Microscopy (SEM) test on 30 pieces of fractured granite has been researched by using S250MK III SEM under triaxial compression of different temperature (25~1000°C) and confining pressure (0~40 MPa). Research results show that (1) the change of fractal dimension (FD) of rock fracture with temperature is closely related to confining pressure, which can be divided into two categories. In the first category, when confining pressure is in 0~30 MPa, FD fits cubic polynomial fitting curve with temperature, reaching the maximum at 600°C. In the second category, when confining pressure is in 30~40 MPa, FD has volatility with temperature. (2) The FD of rock fracture varies with confining pressure and is also closely related to the temperature, which can be divided into three categories. In the first category, FD has volatility with confining pressure at 25°C, 400°C, and 800°C. In the second category, it increases exponentially at 200°C and 1000°C. In the third category, it decreases exponentially at 600°C. (3) It is found that 600°C is the critical temperature and 30 MPa is the critical confining pressure of granite. The rock transfers from brittle to plastic phase transition when temperature exceeds 600°C and confining pressure exceeds 30 MPa.

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Fractal Dimension of Fracture Surface in Rock Material after High Temperature

Cited by 14 publications

References 4 publications

Mineral Composition, Pore Structure, and Mechanical Characteristics of Pyroxene Granite Exposed to Heat Treatments

Mineral Composition, Pore Structure, and Mechanical Characteristics of Pyroxene Granite Exposed to Heat Treatments

Fractal Geometry and Porosity

Fractal Characteristics of Rock Fracture Surface under Triaxial Compression after High Temperature

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