On the Occurrence of Anhydrite in the Sulphatic Claystones of the Gypsum Keuper

Anagnostou, Georg; Serafeimidis, Konstantinos; Vrakas, Apostolos

doi:10.1007/s00603-014-0568-y

Cited by 12 publications

(8 citation statements)

References 24 publications

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“…Dissolved salts and minerals other than calcium sulfate modify the saturation concentrations of gypsum and anhydrite. Recent contributions on this topic (Serafeimidis & Anagnostou, 2013Anagnostou et al, 2015) report the effect of the solute mineralogical content on gypsum or anhydrite equilibrium concentrations.…”

Section: Rock Damagementioning

confidence: 99%

Hydro-chemo-mechanical modelling of tunnels in sulfated rocks

2017

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Permission is granted by ICE Publishing to print one copy for personal use. Any other use of these PDF files is subject to reprint fees.A modelling procedure to address the tunnel–anhydritic rock interaction is described in this paper. The model incorporates the basic physico-chemical phenomena involved in rock swelling, often observed during excavation and subsequent operation of tunnels. It includes (a) a provision for rock damage during tunnel excavation, (b) the precipitation of gypsum crystals in discontinuities and (c) a stress-dependent relationship between swelling strains and mass of gypsum precipitation. The model includes hydro-mechanical coupling and the transport of sulfate salts dissolved in the massif water. Rock damage is described by the development of a network of fractures that increases permeability and allows gypsum crystal growth. Field information, laboratory data and monitoring records available for Lilla tunnel, located in the province of Tarragona, Spain and excavated in Tertiary anhydritic claystone, were selected as a convenient benchmark case to test model capabilities. Predictions and measurements (swelling records of the unlined tunnel floor and swelling pressures against a structural invert) were found to agree reasonably well.Peer ReviewedPostprint (published version

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Section: Rock Damagementioning

confidence: 99%

Hydro-chemo-mechanical modelling of tunnels in sulfated rocks

2017

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“…As discussed, e.g., by Anagnostou et al (2014), a low activity W a of the pore water can inhibit AGT. The water activity is defined as the ratio between the partial evaporation pressure in the vicinity of the pore (p D ) to the saturated evaporation pressure over dilute water (p S ).…”

Section: Influence Of the Activity And Pore Water Potentialmentioning

confidence: 92%

“…They found the solubility of gypsum to increase in the presence of clays and in the case of small pores. Anagnostou et al (2014) then investigated, why anhydrite rather than gypsum is found at small depths of cover, which is usually the case in tunneling and came to the conclusion that the clay minerals and thus the low water activity are most likely responsible for the anhydrite to be the thermodynamically stable phase, rather than gypsum, thus preventing AGT prior to the excavation of tunnels. They used thermodynamic computations to determine the crystallization pressure of gypsum and found that the pressures are considerably lower in the case of low water activities (Serafeimidis and Anagnostou, 2014a).…”

Section: Modelling Of Anhydritic Swelling Claystones -Theoretical Partmentioning

confidence: 99%

“…The stress and the pore water pressure acting on the rock influence the equilibrium concentrations as well. This too was thoroughly discussed by Anagnostou et al (2014). In Figure 2-5 the equilibrium concentrations for anhydrite and gypsum were computed in dependence of the total stress acting on the rock, for two values of the pore water pressure (i.e., 0 and 20 MPa).…”

Section: Influence Of Stress and Pore Water Pressurementioning

confidence: 99%

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Experimental investigations for the modelling of anhydritic swelling claystones

Wanninger¹

2020

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Anhydritic claystones are highly problematic for underground construction because of their swelling ability: When the rock comes into contact with water, the rock volume expands due to swelling of both clay as well as anhydrite. When the expansion is restricted, e.g., by an invert arch in tunneling, the swelling rocks can exert high pressures on the lining and damage the structure. The swelling behavior of purely argillaceous rock (containing solely swelling clays and no anhydrite) can be attributed mainly to osmotic processes and is well understood for the conceptual design of tunnels, as opposed to the swelling of anhydrite, where considerable knowledge gaps exist. Swelling of anhydrite is caused by chemical processes: The anhydrite dissolves when it comes into contact with water, and from the dissolved ions in the pore water gypsum precipitates. The volume of gypsum is greater than that of anhydrite by 61%. During Anhydrite to Gypsum Transformation (hereafter denoted as AGT) the rock mass expands and the pore volume can also increase, for example due to cracking of the rock induced by the pressure exerted by the growing crystals upon a rigid rock structure ("crystallization pressure"). This PhD thesis seeks to establish a better understanding and quantification of the coupled chemomechanical swelling processes due to AGT and creates a basis for developing chemo-mechanical models of the swelling of anhydritic claystones. The findings from the experiments verified kinetic models and assumptions related to AGT. Moreover, the systematic experimental investigations regarding the swelling behavior of anhydrite give an indication of a stress-strain relationship which can be implemented and used as a fundamental basis for future modelling of swelling due to AGT. This is necessary for practicing engineers in order to design underground structures in anhydritic rock. Furthermore, it was shown that the swelling due to anhydrite and clay can be de-coupled by varying the testing temperatures, which changes the equilibrium concentrations.

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“…Earlier studies focused mainly on the formation of natural mineral deposits and applications in the building industry, that is, for gypsum targeting and mining. More recent work, however, has investigated the reaction kinetics as well as the critical geochemical conditions (Anagnostou et al, ; Serafeimidis & Anagnostou, ), including the effect of regional groundwater flow and hydrological boundary conditions, that impact the swelling of clay‐sulfate rocks (Butscher, Huggenberger et al, ; Butscher, Huggenberger, Einstein et al, ). Furthermore, several numerical models have been proposed, including models that couple hydrological, chemical, and mechanical processes, to simulate the swelling of such rocks.…”

Section: Introductionmentioning

confidence: 99%

Reactive Transport Modeling of Swelling Processes in Clay‐sulfate Rocks

Schweizer

Prommer

Blum

et al. 2018

Water Resources Research

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Swelling of clay‐sulfate rocks often causes large problems in geotechnical applications such as tunneling. The primary mechanism inducing the increase in rock volume is the chemical transformation of anhydrite to gypsum, which is triggered by the ingress of groundwater. In the present study, a novel conceptual and numerical modeling approach is developed that emphasizes the effect of groundwater flow in conjunction with the associated availability of water and changing geochemical conditions on the chemical transformation of anhydrite to gypsum. A reactive transport model was developed and hydraulic, reactive, and solute transport as well as mechanical model parameters were estimated through an inversion process, constrained by geodetic ground heave measurements from a study site in Staufen, Germany. The conceptual model of the swelling process was implemented numerically through a dual‐domain modeling approach, whereby the mobile domain accounts for solute transport along discontinuities, and the immobile reactive domain represents the matrix. A mass transfer process accounts for diffusive and/or capillary water transport into the matrix, where the rate‐limited transformation of anhydrite to gypsum takes place. The model calculates heave at the land surface depending on water inflow, the transformation of anhydrite into gypsum and the local stress conditions exerted by overburden pressure. The results show that the proposed reactive transport modeling approach is suitable to quantify the observed swelling‐induced heave at the study site with a plausible parameterization. The study also highlights that diffusion is a decisive factor for the effective rate of anhydrite dissolution and, therefore, the overall chemical transformation process.

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On the Occurrence of Anhydrite in the Sulphatic Claystones of the Gypsum Keuper

Cited by 12 publications

References 24 publications

Hydro-chemo-mechanical modelling of tunnels in sulfated rocks

Hydro-chemo-mechanical modelling of tunnels in sulfated rocks

Experimental investigations for the modelling of anhydritic swelling claystones

Reactive Transport Modeling of Swelling Processes in Clay‐sulfate Rocks

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