Swelling laws for clay-sulfate rocks revisited

Butscher, Christoph; Breuer, Simon; Blum, Philipp

doi:10.1007/s10064-016-0986-z

Cited by 13 publications

(6 citation statements)

References 21 publications

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“…Anhydrite turns into gypsum when it comes into contact with water. The transformation process is accompanied by a volume increase of up to 61% (Butscher et al 2016a). The swelling process occurred relatively slowly due to its kinetics and medium-tolow hydraulic permeability in this zone (Sass and Burbaum 2010;Butscher et al 2016b).…”

Section: Methodsmentioning

confidence: 99%

Damage event analysis of vertical ground source heat pump systems in Germany

Fleuchaus

Blum

2017

Geotherm Energy

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Section: Methodsmentioning

confidence: 99%

Damage event analysis of vertical ground source heat pump systems in Germany

Fleuchaus

Blum

2017

Geotherm Energy

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“…The clay-sulfate rock collected in Gansu is a typical redbed semi-rocks that belongs to both clay-bearing rock and sulfate-bearing rock. The sulfate in the rocks is partly hydrated and the cementation of the mineral is weak, which is different from the clay-sulfate rocks with high content of anhydrite in Germany and Switzerland (Steiner, 1993;Pimentel, et al 2013;Butscher, et al 2018). Meanwhile, its hydraulic properties are more complex, because the content of carbonate minerals is high.…”

Section: Introductionmentioning

confidence: 94%

Experimental investigation on the expansive characteristics of Gansu clay-sulfate rocks in China subjected to confined compression and cyclic drying-wetting

Cheng

Zeng

Yang

et al. 2022

Preprint

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Gansu clay-sulfate rock is a special red-bed rock that formed in an evaporation environment with strong oxidation. Due to the high content of hydrophilic minerals (including clay mineral, sulfate, and carbonate), tunnel in clay-sulfate rock stratum has a potential risk of large expansive deformation after the erosion of groundwater. In this study, a loadable cyclic drying-wetting instrument was designed to simulate the occurrence of the surrounding rock mass of a tunnel experiencing a periodic change in groundwater level. Firstly, a series of drying-wetting cycle tests with different normal pressure were carried on to obtain the expansion regulation of clay-sulfate rock. Then, computed tomography (CT) and scanning electron microscope (SEM) tests were carried on to explain the corresponding mechanism in mesoscopic. The test results show that large expansive deformation was generated in the first water immersion and only part of the deformation can be recovered during the later drying process. During the 2–5 cycles, expansion-shrink deformation is much less than in the first cycle, and the volume of the sample tends to be constant. Meanwhile, the degeneration of the clay-sulfate rock was observed in the first cycle by the CT and SEM test. Then the mesostructure of the sample is stable during the 2–5 cycle. It indicates the clay rock, in large part, degenerated to clay soil during the first drying-wetting cycle. Structural degradation and hydration of anhydrite is the main source of irreversible expansive deformation. Moreover, normal stress and confined restraint can reduce or even eliminate the expansive deformation, however, cannot avoid the degeneration of mesostructure. The shear strength of Gansu clay-sulfate rock also decreased after the first drying-wetting cycle, which manifested as the attenuation in both cohesion and internal friction angle.

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“…Note that the material properties of the overburden layer have remained unchanged. Ranges of parameter values considered in the sensitivity analysis listed in (Table 2) are not limited to the Staufen site, and were obtained from previous studies (Alonso et al 2013;Butscher et al 2011Butscher et al , 2018Schädlich et al 2013;Wittke 2003). We applied the one-ata-time (OAT) method (Morris 1991) to analyze the influence of changing the values of each chosen parameter separately.…”

Section: Sensitivity Analysismentioning

confidence: 99%

“…Several finite element models have already been developed to address the swelling in various settings in Austria, Germany, Spain, and Switzerland (e.g., Anagnostou 1993;Ramon et al 2017;Schädlich et al 2013;Wittke 2014). Although these models successfully simulated the swelling deformations, their generalization capability remains limited because of the existing gaps in the overall understanding of the swelling process (Butscher et al 2016(Butscher et al , 2018. A lack of knowledge still exists with respect to coupling between hydraulic, mechanical, and chemical processes due to a lack of long-term experiments that would deliver a database for the development of a coupled model (Wanninger 2020).…”

Section: Introductionmentioning

confidence: 99%

Coupled Hydro-Mechanical Modeling of Swelling Processes in Clay–Sulfate Rocks

et al. 2022

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Swelling of clay–sulfate rocks is a serious and devastating geo-hazard, often causing damage to geotechnical structures. Therefore, understanding underlying swelling processes is crucial for the safe design, construction, and maintenance of infrastructure. Planning appropriate countermeasures to the swelling problem requires a thorough understanding of the processes involved. We developed a coupled hydro-mechanical (HM) model to reproduce the observed heave in the historic city of Staufen in south-west Germany, which was caused by water inflow into the clay–sulfate bearing Triassic Grabfeld Formation (formerly Gipskeuper = “Gypsum Keuper”) after geothermal drilling. Richards’ equation coupled to a deformation process with linear kinematics was used to describe the hydro-mechanical behavior of clay–sulfate rocks. The mathematical model is implemented into the scientific open-source framework OpenGeoSys. We compared the model calculations with the measured long-term heave records at the study site. We then designed a sensitivity analysis to achieve a deeper insight into the swelling phenomena. The synthetic database obtained from the sensitivity analysis was used to develop a machine learning (ML) model, namely least-squares boosting ensemble (LSBoost) model coupled with a Bayesian optimization algorithm to rank the importance of parameters controlling the swelling. The HM model reproduced the heave observed at Staufen with sufficient accuracy, from a practical point of view. The ML model showed that the maximum swelling pressure is the most important parameter controlling the swelling. The other influential parameters rank as Young’s modulus, Poisson’s ratio, overburden thickness, and the initial volumetric water content of the swelling layer.

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Swelling laws for clay-sulfate rocks revisited

Cited by 13 publications

References 21 publications

Damage event analysis of vertical ground source heat pump systems in Germany

Damage event analysis of vertical ground source heat pump systems in Germany

Experimental investigation on the expansive characteristics of Gansu clay-sulfate rocks in China subjected to confined compression and cyclic drying-wetting

Coupled Hydro-Mechanical Modeling of Swelling Processes in Clay–Sulfate Rocks

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