On the Time-Development of Sulphate Hydration in Anhydritic Swelling Rocks

Abstract

Anhydritic claystones are among the most problematic rocks in tunnelling. Their swelling has caused serious damage and high repair costs in a number of tunnels, especially in Switzerland and southwest Germany. The swelling is usually attributed to the transformation of anhydrite into gypsum. It is a markedly time-dependent process which might take several decades to complete in nature. The present paper focusses on simultaneous anhydrite dissolution and gypsum precipitation in a closed system, i.e. disregarding the transport processes that may also be important for the evolution of the swelling process. The paper begins with a presentation of the governing equations and continues with parametric studies in order to investigate the role of the initial volumetric fractions of the constituents and the specific surface areas of the minerals involved. A simplified model for the hydration of anhydrite is also proposed, which identifies the governing process and the duration of the swelling process. Finally, parametric studies are performed in order to investigate the effect of the anhydrite surface being sealed by the formation of gypsum. The latter slows down the swelling process considerably.

Chemo-mechanics of salt damage in stone

“…While this was recognized long ago in geomorphology 1,2 and conservation science [3][4][5][6][7] , it has only recently emerged in concrete science as the most convincing explanation for sulfate attack [8][9][10] and in geotechnical engineering for the floor heave of anhydrite-containing rock formations 11 . In the latter case, the most dramatic situation was a geothermal drilling through anhydrite-bearing rock formations that opened access for water to convert anhydrite to gypsum.…”

Assessment of Bearing Capacity and Stiffness in New Steel Sets Used for Roadway Support in Coal Mines

“…), when interacted with air and water, become continuously and highly deformable [21]. Roadway support in swelling soft rocks has become one of the challenging mining problems in recent years [22][23][24][25][26][27]. Chagannuoer coal field is a typical swelling soft rock field in Inner Mongolia of China.…”

Deformation mechanisms in a coal mine roadway in extremely swelling soft rock

“…Roadway control in soft rock is a problem in many mines (Bilir 2011; Ghiasi et al 2012; Serafeimidis and Anagnostou 2013; Thomas et al 2013). For roadway control, a variety of support materials and structures have been developed, such as arch sheds, bolting, cables, and shotcrete (Goetze 1984; Okubo et al 1984; Rotkegel 2001; Stalega 1995).…”

“…The problem of roadway support in swelling soft rock has become a challenging problem in recent years (Bilir 2011; Ghiasi et al 2012; Schädlich et al 2013; Serafeimidis and Anagnostou 2013; Thomas et al 2013). In swelling soft rock, support measures include either, the application of a strong, rigid supporting formwork to limit deformation, or allowing floor heave to release swelling pressures, or a combination of both (Christoph et al 2011).…”