Real-time SEM observation of mesoscale failures under thermal-mechanical coupling sequences ingranite

 Xue Dongjie●Zhou Hongwei●Zhao Yongwei●Zhang Liao●Deng Linsheng●Wang Xiangyu 

Abstract

The thermal-mechanical (TM) coupling sequences on failure can provide a bridge for theoretical understanding and numerical modeling, not only dependent on the thermal expansion coefficient Based on the designed three sequences of TM coupling on the meso-scale, uniaxial tension experiments combined with Scanning Electron Microscopy (SEM) are performed for granite. The real-lime observation of crack generation, propagation and connection indicates the complexity under three coupling sequences. The results show that the TM description effectively should be consideration on the meso parameters, i.e. crack number with the fractal dimension, crack length and spacing. There is a critical temperature of 175 degrees C for mesoscale granite. The temperature shows an exponential increasing on the meso parameters below the critical temperature, and a linear decreasing above the critical value. There is also an observation of brittle-ductile transition under the TM coupling based on the stress-strain curve and the fractured patents. There are two different cracking forms of the transgranular crack caused by the stress loading, and the intergranular crack caused by the thermal loading. Considering the thermal effect on the meso parameters, there is an exponential relationship between the tension strength and the meso parameters. It provides a bridge for understanding the relationship between temperature and the tension strength via mesoscale parameters. Finally, the experimental results are verified by the numerical simulation on the grain scale. The numerical modeling of TM coupling sequences shows that the effect description ofstress-strain relationship needs a consideration of the meso parameters based on the grain scale structure of mineral particle.

引用格式：

Xue DJ, Zhou HW, Zhao YW, Zhang L, Deng LS, Wang XY . Study of Drainage and Percolation of Nitrogen–Water Flooding in Tight Coal by NMR Imaging[J]. Rock Mechanics and Rock Engineering, 2018: 1-17. 

SCI:WOS- 000452314500005     DOI:10.1016/j.ijrmms.2018.10.020

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