Precipitation triggered rock dynamics: the missing mesoscopic link

ongoing

Climate change leads to increasing weathering cycles on landscapes and the built environment. Promotion of alternative energy sources such as geothermal energy intensifies cyclic perturbations of the underground environment. Both lead to precipitation-dissolution cycles of salts, natural constituents of brines present inside porous rock. When precipitation occurs inside the pores, stresses build up which eventually crack the material. This might be a positive outcome, e.g., increasing the production rate of a geothermal reservoir, or on the contrary, be the cause of severe deterioration of natural building stones and coastal erosion. What is the actual trigger for the dynamic response of a rock when precipitation occurs, and can we ultimately control this trigger? The answer lies at the meso-scale, i.e. the scale of the pore network, where precipitation-dissolution reactions, geometry changes and flow and transport properties changes meet. These reactions and changes are strongly coupled, but their respective importance for the resulting rock dynamics is unclear. A combined experimental-modelling approach will be developed, comprising: (1) 4D X-ray micro-tomographic experiments providing new insights in the correlations between transport-precipitation-deformation processes inside rock; (2) a virtual simulator for precipitation-triggered rock dynamics based on a unified phase-field description; (3) a model-based image analysis approach, combining the simulator and the experimental dataset through a Bayesian framework for properties and constitutive model identification and hierarchization. This hierarchization will pinpoint the governing trigger(s). By acting on the trigger, controlled precipitation-induced cracking and crack healing will be demonstrated on core-scale rocks. The new experimental-modelling toolset will open new ways for improving building stones’ durability, cultural heritage and coastal protection, and geoengineering of the subsurface.