Dynamic experimental study on rock meso-cracks growth by digital image processing technique

Abstract

A new meso-mechanical testing scheme based on SEM was developed to carry out the experiment of microfracturing process of rocks. The microfracturing process of the pre-crack marble sample on surrounding rock in the immerged Long-big tunnel in Jinping Cascade II Hydropower Station under uniaxial compression was recorded by using the testing scheme. According to the stereology theory, the propagation and coalescent of cracks at meso-scale were quantitatively investigated with digital technology. Therefore, the basic geometric information of rock microcracks such as area, angle, length, width, perimeter, was obtained from binary images after segmentation. The failure mechanism of specimen under uniaxial compression with the quantitative information was studied from macro and microscopic point of view. The results show that the image of microfracturing process of the specimen can be observed and recorded digitally. During the damage of the specimen, the distribution of microcracks in the specimen is still subjected to exponential distribution with some microcracks concentrated in certain regions. Finally, the change law of the fractal dimension of the local element in marble sample under different external load conditions is obtained by means of the statistical calculation of the fractal dimension.

Keywords

marble / rock failure process / digital image processing / growth of meso-crack / dynamic observation / experimental study

References

[1] MichaelE. K., SiaN. N., SuoZ. G.. New directions in mechanics [J]. Mechanics of Materials, 2005, 37: 231-259

[2] YossefH. H., AlonZ., YaakovM.. Microstructure effects on microcracking and brittle failure of dolomites [J]. Tectonophysics, 1997, 281: 141-161

[3] WuX. Y., BaudP. W.. Micromechanics of compressive failure and spatial evolution of anisotropic damage in Darley Dale sandstone Teng-fong [J]. International Journal of Rock Mechanics and Mining Sciences, 2000, 37(1): 143-160

[4] PASCAL D, MICHEL B. Micromechanical application of digital speckle correlation techniques [M]. Springer-Verlag, 2000: 67–74.

[5] DwivediR. D., GoelR. K., PrasadV. V. R., Amalendu SinhaA. S.. Thermo-mechanical properties of Indian and other granites [J]. International Journal of Rock Mechanics and Mining Sciences, 2008, 45(3): 303-315

[6] ZhaoY.-h., HuangJ.-f., WangR.. Real time observation of microfracturing process in rock during compression test [J]. Chinese Journal of Rock Mechanics and Engineering, 1992, 11(3): 284-294

[7] ZhaoY.-h., HuangJ.-f., WangR.. SEM study of fracture development in compressed marble specimen and implications for earthquake precursors [J]. Chinese Journal of Geophysics, 1993, 6(4): 453-462

[8] ZhaoY.-h., HuangJ.-f., HouJ.-jun.. Experimental study of meso-fractures in rock and its implication for understating seismic activities [J]. Chinese Journal of Geophysics, 1995, 38(5): 627-635

[9] LiL., TsuiY., LeeP. K. K.. Progressive cracking of granite plate under uniaxial compression [J]. Chinese Journal of Rock Mechanics and Engineering, 2001, 21(7): 940-947

[10] WangZ.-y., LiuL., LiuB.-xian.. Characteristics of damage evolution of micropore and microcrack in rock [J]. Chinese Journal of Rock Mechanics and Engineering, 2004, 23(10): 1599-1603

[11] ZhaoP., XieW.-h., WangX.-s., CaoF.. The real time experimental research on rock’s SEM under high temperature [J]. Mechanics in Engineering, 2006, 28(3): 64-67

[12] XieW.-h., GaoF., LiS.-c., GuanX.-hui.. Study on mechanism of thermal damage fracture for limestone [J]. Rock and Soil Mechanics, 2007, 28(5): 1021-1025

[13] ZhuZ.-d., QuW.-p., JiangZ.-jian.. Quantitative test study on mesostructure of rock [J]. Chinese Journal of Rock Mechanics and Engineering, 2007, 26(7): 1313-1324

[14] QuW.-ping.Quantitative mesostructure investigation of rock based on digital image processing technique [D], 2006, Nanjing, Hohai University

[15] LiD.-wei.Mesomechanics experimental research on surrounding rock in immerged long-big tunnel [D], 2008, Nanjing, Hohai University: 121-125