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

Abstract

The microstructures of rock gradually evolve with changes in the external environment. This study focused on the microstructure evolution of glauberite and its weakening mechanism under different leaching conditions. The porosity were used as a characteristic index to study the effect of brine temperature and concentration on crack initiation and propagation in glauberite. The research subjects were specimens of ϕ3 × 10 mm cylindrical glauberite core, obtained from a bedded salt deposit buried more than 1000 m underground in the Yunying salt formation, China. The results showed that when the specimens were immersed in solution at low temperature, due to hydration impurities, cracks appeared spontaneously at the centre of the disc and the solution then penetrated the specimens via these cracks and dissolved the minerals around the crack lines. However, with an increase of temperature, the dissolution rate increased greatly, and crack nucleation and dissolved regions appeared simultaneously. When the specimens were immersed in a sodium chloride solution at the same concentration, the porosity s presented gradual upward trends with a rise in temperature, whereas, when the specimens were immersed in the sodium chloride solution at the same temperature, the porosity tended to decrease with the increase of sodium chloride concentration. In the process of leaching, the hydration of illite, montmorillonite, and the residual skeleton of glauberite led to the expansion of the specimen volume, thereby producing the cracks. The diameter expansion rate and the expansion velocity of the specimen increased with temperature increase, whereas, due to the common-ion effect, the porosity of the specimen decreases with the increase of sodium chloride solution concentration.

Influencing Factors for the Instability and Collapse Mode of the Goaf Structure in a Gypsum Mine

“…e goafs of a gypsum mine created by the room pillar method often remain intact for several years or even decades before collapse. Under long-term stress, the stability and lag collapse of a gypsum mine goaf depend to a large extent on the ultimate support capacity of the gypsum ore pillars over time [42][43][44][45][46][47].…”

Experimental study on the effect of thermal-chemical coupling on tension-shear fracture characteristics of cracked Karst limestone

“…In addition, the influence of acid solution on the macro mechanical properties of jointed rock mass is investigated (Chen et al2019;Feng et al2001;Yu et al 2020) and the relationship between micro deterioration and macro mechanical properties of rocks in different acidic environment have been also studied by way of different experimental test for soaking granite, sandstone, limestone and other rock samples in acid solution Huang et al 2021;Li et al 2018;Liu et al 2022;Miao et al 2016;Mo et al 2022;Wu et al2022). The microstructure evolution of intact rock samples under the coupled thermal-hydro-chemical environment has gradually attracted the attention of researchers (Chen et al 2018;Meng et al 2021;Wei et al 2022). For example, a mechanical apparatus is designed for testing the evolution law and fluctuation mechanism of permeability and pore structure of hot dry rocks (HDR) with the coupling of high temperatures and high triaxial stress (Meng et al 2021;Wei et al 2022).…”