Problems of Evolving Porous Media and Dissolved Glauberite Micro-scopic Analysis by Micro-Computed Tomography: Evolving Porous Media (1)

Abstract

In this study, the evolution phenomena and mechanism of porous media were analyzed according to the driving factors, i.e., external force, heat, seepage, coupled chemical reaction and seepage, coupled chemical reaction and heat flow, and live porous media. According to the evolution mechanism, the evolution can be categorized as natural evolution, artificial evolution, and natural-artificial evolution. Taking the dissolution of glauberite ore as the example, the detailed evolution characteristics and behavior were investigated. The evolution characteristics of pores and the residual porous skeleton were investigated using micro-computed tomography. The results indicate that (1) The variation of the dissolution thickness of glauberite with time follows a power function. (2) The total void ratio of the residual porous media remains almost the same and is typically in a range of 20-22 %. The diffusion coefficient of the residual porous skeleton is 0.013 cm 2 /h. (3) In the process of glauberite dissolution, three zones are formed from the interface to the outside: a crystallization completion zone, a crystalline transition zone, and a development zone of dissolution and crystallization. The crystallization completion zone is formed after 15 h dissolution. The thickness of the crystallization transition zone and development zone of dissolution and crystallization is approximately 0.5-1.0 mm.

Experimental Study of the Microstructural Evolution of Glauberite and Its Weakening Mechanism under the Effect of Thermal-Hydrological-Chemical Coupling

“…Eventually, the sodium sulphate would be completely dissolved and removed, whereas the calcium sulphate would completely become the residual skeleton. Dissolution of a small salt-gypsum specimen by pure water after different immersion times [19]. Images were made using MCT (250×).…”

“…Images were made using MCT (250×). Dissolution of a small salt-gypsum specimen by pure water after different immersion times [19]. Images were made using MCT (250×).…”

“…They concluded that pressure solution in gypsum is controlled by the precipitation reaction, and diffusion is unlikely to be the rate-controlling mechanism of pressure solution. Zhao et al [19] investigated evolution characteristics of pores and the residual porous skeleton of glauberite, and concluded that three Several researchers previously concentrated on the effect of external environment on rock microstructures under the THC coupling effect. Meer et al [18] have discussed the microstructure evolution of gypsum in the present of saline pore fluid and NaCl-free pore fluid.…”

“…They concluded that pressure solution in gypsum is controlled by the precipitation reaction, and diffusion is unlikely to be the rate-controlling mechanism of pressure solution. Zhao et al [19] investigated evolution characteristics of pores and the residual porous skeleton of glauberite, and concluded that three zones are present from dissolution interface to the outside in the process of glauberite dissolution. Zhang et al [14] studied the cementation state and the grain arrangement mode of the halite and salt interlayers with scanning electron microscope analyses.…”

Multi-scale characteristics of coal structure by x-ray computed tomography (x-ray CT), scanning electron microscope (SEM) and mercury intrusion porosimetry (MIP)

“…By using X-ray CT scanning, coal skeleton deformation and pores/fractures evolving in rock materials under different testing conditions were extensively obtained. [16][17][18][19] Besides, on the basis of threshold segmentation and 3-D reconstructions, the qualitative visualization and pore structure quantitative characterization can be performed, too. 20,21 As for scanning electron microscopy (SEM), it works in larger magnification and can accurately shows more detailed material composition and structural characterization information, thus it is widely used in the morphology study of rock and soil materials.…”