Title: A Gaussian process regression model to determine solubility of calcium sulfate in aqueous fluids

Ali Sadighi, Reza Taherdangkoo, Christoph Butscher

TU Bergakademie Freiberg, Institute of Geotechnics, Gustav-Zeuner-Str. 1, 09599 Freiberg, Germany

Event: GeoKarlsruhe 2021

Date: 2021

DOI: 10.48380/dggv-q937-na63

The swelling of clay-sulfate rocks is a well-known phenomenon often causing threats to the success of different projects, for instance, geothermal drillings triggered swelling and ground heave with dramatic damages in Staufen, Germany. The origin of clay-sulfate swelling is usually explained by physical swelling due to clay expansion combined with chemical swelling associated with the transformation of anhydrite (CaSO4) into gypsum (CaSO4.2H2O). The swelling leads to about 60% of the volume increase of the rock mass. Numerical models simulating rock swelling must consider hydraulic, mechanical, and chemical processes. The simulation of the chemical processes is performed by solving thermodynamic equations usually contributing a significant portion of the overall simulation time. This contribution presents a Gaussian process regression (GPR) model as an alternative approach to determine the solubility of mineral phases, i.e., anhydrite and gypsum, in pore water. The GPR model is developed using the experimental data collected from the literature. The GPR predicts the solubility of the sulfate minerals with a degree of accuracy needed for typical subsurface engineering applications.

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