Experimental analysis of the water retention behaviour of shales

Ferrari, Alessio; Favero, Valentina; Marschall, Paul; Laloui, Lyesse

doi:10.1016/j.ijrmms.2014.08.011

Cited by 104 publications

(55 citation statements)

References 28 publications

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“…Diese aus-trocknungsbedingten Schrumpfungsspannungen sind größer als die vormaligen Überlagerungsspannungen [8], [10]. Als eine mögliche Erklärung können vielleicht volumenbezogene Veränderungen im Porenraumsystem vermutet werden, die zunächst durch Schrumpfung relativ großer Poren und dann durch anschließendes, teilweises Wiederaufquellen (mit teilweisem Ausgleich des Schrumpfvolumens) zu Veränderungen eines Teils der Porenquerschnitte führen.…”

Section: Methodik Probenahme Und Vorbereitendes Untersuchungsprogrammunclassified

Tonstein als Wirtsgestein: Ein geomechanischer Beitrag über Opalinuston

2016

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Der Opalinuston ist ein prominenter Vertreter der organikhaltigen Tonsteine oder Schiefertone, die in der Schichtenfolge aus Trias und Jura regional ein mehrere Zehnermeter mächtiges, relativ homogenes Schichtpaket bildet. In Abhängigkeit vom Verfestigungsgrad der Pelitgesteine variieren die geomechanischen Parameter Scherfestigkeit, Zugfestigkeit und Durchlässigkeit, die bei einer zu diskutierenden Nutzung als Wirtsgestein für die Lagerung radioaktiver Abfälle auch bautechnische Bedeutung erlangen. Ein Tunnelvortrieb im Opalinuston bot die eher seltene Gelegenheit, Proben aus unverwittert frischen Schiefertonen in größerem Umfang als bei üblichen Bohrungen zu gewinnen. Es werden geomechanische Laborversuche, insbesondere mehrstufige, triaxiale Kompressionsversuche und Hydraulic‐Fracturing‐Versuche an definiert räumlich eingespannten Quaderproben ausgewertet, um Scherfestigkeit, hydraulische Zugfestigkeit sowie Durchlässigkeits‐ bzw. Abdichtungseigenschaften des Opalinustons zu charakterisieren. Einführend wird in diesem Kontext die Bedeutung des Sättigungszustands und dessen Veränderlichkeit diskutiert. Die ermittelten geomechanischen Parameter werden verglichen mit vormals höher und mit ähnlich beanspruchten, äußerlich gleich erscheinenden Pelitgesteinen aus Japan und aus der Schweiz. Clay shale as host rock: a geomechanical contribution about Opalinus clay. The Opalinuston is a prominent rock representing the type of organic clay shales or clay stones within the sequence of Triassic and Jurassic marine sediments in Southern Germany. The rock forms a homogenous unit some ten meters thick. The degree of consolidation of this type of pelitic rock depends mainly on the former load conditions, but is also dependent on the long‐term weathering and even on the present exposition. The geomechanical parameters such as shear strength, tensional strength and permeability vary with the state of consolidation and become important when the use is discussed of such rocks for radioactive waste disposal. A tunneling project at the northern escarpment of the Swabian Alb (Southwest Germany) within the Opalinus clay offered the rare opportunity to obtain fresh unweathered rock samples in greater amounts compared to fresh drilling cores from which geomechanical investigations are usually undertaken. Consequently, the results of geomechanical laboratory testings are presented in order to compare here the results of multistep triaxial compression tests, of hydraulic fracturing laboratory tests and of some other tests for rock characterization with the corresponding results of Opalinus clay sites in Switzerland that were investigated by the Swiss Nagra Company for host rock characterization. After a discussion of the relevant state of fresh Opalinus clay, especially of suction pressure conditions and saturation state, the results of triaxial shear tests are presented. Increasing shear deformation at increasing pressure and unchanged water saturation do not result in a significant strength reduction of the Opalinus clay. The ...

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Section: Methodik Probenahme Und Vorbereitendes Untersuchungsprogrammunclassified

Tonstein als Wirtsgestein: Ein geomechanischer Beitrag über Opalinuston

2016

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“…Opalinus Clay contains 40-80% clay minerals, is a mixture of kaolinite, chlorite, illite and illite/smectite mixed layer phases, and is expected to have significant swelling capacity (swelling pressure perpendicular to stratification is 0.8-1.4 MPa) and suction potential (Ferrari et al 2014). The latter causes the clay to take up water until it is saturated, at which point the suction potential is zero.…”

Section: General Factors Restricting Microbial Activity In Opalinus Claymentioning

confidence: 99%

Fifteen years of microbiological investigation in Opalinus Clay at the Mont Terri rock laboratory (Switzerland)

et al. 2017

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Microbiological studies related to the geological disposal of radioactive waste have been conducted at the Mont Terri rock laboratory in Opalinus Clay, a potential host rock for a deep geologic repository, since 2002. The metabolic potential of microorganisms and their response to excavation-induced effects have been investigated in undisturbed and disturbed claystone cores and in pore-(borehole) water. Results from nearly 15 years of research at the Mont Terri rock laboratory have shown that microorganisms can potentially affect the environment of a repository by influencing redox conditions, metal corrosion and gas production and consumption under favourable conditions. However, the activity of microorganisms in undisturbed Opalinus Clay is limited by the very low porosity, the low water activity, and the largely recalcitrant nature of organic matter in the claystone formation. The presence of microorganisms in numerous experiments at the Mont Terri rock laboratory has suggested that excavation activities and perturbation of the host rock combined with additional contamination during the installation of experiments in boreholes create favourable conditions for microbial activity by providing increased space, water and substrates. Thus effects resulting from microbial activity might be expected in the proximity of a geological repository i.e., in the excavation damaged zone, the engineered barriers, and first containments (the containers).

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“…The results of the geotechnical identification of the cores are reported in Table 1 while Fig.1 depicts the grain size distributions of the considered shales [1]. The pore size density (PSD) function of the tested shale cores is determined through the Mercury Intrusion Porosimetry (MIP); this technique consists in forcing the penetration of mercury into a sample and in measuring the intruded volume of mercury as a function of the applied pressure.…”

Section: Tested Shalesmentioning

confidence: 99%