Effect of Thermal Treatment on Fractals in Acoustic Emission of Rock Material

Tunnel fire is a part of applied thermal problems. With increase of transient temperature of the tunnel fire on the structure surface (i. e. tunnel lining), the heat transfer from the surface is possibly varying transient temperature distribution within the structure. The transient temperature distribution is also possibly damaging the composition of structure (micro-crack) because of critical damage temperature. Therefore, the transient temperature distribution has a significantly important role on defining mechanical and physical properties of structure and determining thermal-induced damaged region. The damage at pre-period stage of tunnel fire is perhaps more significant than that at the other period stages because of thermal gradient. Consequently, a theoretical model was developed for simplifying complicated thermal engineering during pre-period stage of tunnel fire. A hollow solid model in a combination of dimensional analysis and heat transfer theory with Bessel's function and Duhamel's theorem were employed to verify a theoretical equation for dimensionless transient temperature distribution under linear transient thermal loading. Experimental and numerical methods were also adopted to approve the results from this theoretical equation. The heating rate is a primary variable for discussing dimensionless transient temperature distribution on three means. The heating rate of 10191.10 and 240 °C/min were applied to experimental and numerical studies. The experimental and numerical results are consistent with the theoretical solution, successfully verifying that the theoretical solution can predict the dimensionless transient temperature distribution well in field. This equation can be used for thermal/tunnel engineers to evaluate the damaged region and to obtain the parameters related to dimensionless transient temperature distribution.

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“…According to the Duhamel's theorem [18,22,23,27] for LTTL, the dimensional approaching solution of DTTD obtained by imposing eqs. (6) and (16):…”

Section: Dimensionless Temperature Distribution Of a Hollow Solid Undmentioning

confidence: 99%

“…1. Those issues are directly related to heat transfer and temperature distribution in solids [9,[11][12][13][14][15][16][17]. Understanding the heat transfer process can predict and prevent the damage in solids during structure service period, which is significant for the structure safety.…”

Section: Introductionmentioning

confidence: 99%

Heat transfer on simplified pre-period stage of tunnel fire

Liu

Yao

2019

THERM SCI

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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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“…In recent years, AE detection technology has been used in rock mechanics by many scholars [20][21][22][23][24][25][26][27]. For example, Ganne et al [20] studied the brittleness of rock before peak stress by the AE technique, and four stages of accumulated AE energy were given.…”

Section: Introductionmentioning

confidence: 99%

“…Zhang et al [25] studied AE properties of halite, glauberite, and gypsum during compression test with different loading styles and saturation conditions. Zhang et al [26] calculated the correlation fractal dimensions of AE counts at different stress levels, and the value at the failure point showed a polynomial decline with the increase of temperature. Guo et al [27] carried out comprehensive studies on rockdetected AE characteristics, failure mode, crack initiation stress, damage evolution law, and stress-strain constitutive model after thermal damage.…”

Section: Introductionmentioning

confidence: 99%

Acoustic Emission and Damage Characteristics of Granite Subjected to High Temperature

Zhang

2018

Advances in Materials Science and Engineering

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Acoustic emission (AE) signals can be detected from rocks under the effect of temperature and loading, which can be used to reflect rock damage evolution process and predict rock fracture. In this paper, uniaxial compression tests of granite at high temperatures from 25°C to 1000°C were carried out, and AE signals were monitored simultaneously. e results indicated that AE ring count rate shows the law of "interval burst" and "relatively calm," which can be explained from the energy point of view. From 25°C to 1000°C, the rock failure mode changes from single splitting failure to multisplitting failure, and then to incomplete shear failure, ideal shear failure, and double shear failure, until complete integral failure. ermal damage (D T ) defined by the elastic modulus shows logistic increase with the rise of temperature. Mechanical damage (D M ) derived by the AE ring count rate can be divided into initial stage, stable stage, accelerated stage, and destructive stage. Total damage (D) increases with the rise of strain, which is corresponding to the stress-strain curve at various temperatures. Using AE data, we can further analyze the mechanism of deformation and fracture of rock, which helps to gather useful data for predicting rock stability at high temperatures.

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Effect of Thermal Treatment on Fractals in Acoustic Emission of Rock Material

Cited by 13 publications

References 18 publications

Heat transfer on simplified pre-period stage of tunnel fire

Heat transfer on simplified pre-period stage of tunnel fire

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

Acoustic Emission and Damage Characteristics of Granite Subjected to High Temperature

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