Coupled thermo-hydraulic pulse tests on two reference Belgian clay formations

Lima, Ana Carolina Oliveira; Romero, E.; Solé, Antonio Gens; Vaunat, Jean; Li, X.L.

doi:10.1201/b15004-53

Cited by 3 publications

(5 citation statements)

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“…However, to highlight these new fully undrained results, it should be emphasised that they were obtained under a very small range of temperature change (a temperature change of 9ºC at the heater), compared to previous results [18] that were obtained at a larger temperature range of the heater (39ºC) and under controlled backpressure at the bottom boundary (1.20 MPa). In addition, it is important to indicate that these values are higher than those reported for Boom Clay on heating [10,18] and those presented in Table 2 for stiffer argillaceous formations (Opalinus claystone and Callovo-Oxfordian Clay).…”

Section: Results and Interpretationmentioning

confidence: 83%

“…There is a large variability of the thermal pressurisation coefficient depending upon the nature of the material −associated with the stress-state dependency and induced damage affecting its drained compressibility − as well as on the range of the temperature change − the fluid thermal expansion is temperature-dependent. For example, values of the thermal pressurisation coefficient on heating between 0.06 and 0.192 MPa/ºC have been reported for Boom Clay by [9] and [10], respectively. Table 1 summarises different theoretical and experimental values of the thermal pressurisation coefficients Ʌ (MPa/ºC) for different geomaterials.…”

Section: Introductionmentioning

confidence: 99%

“…Table 1 summarises different theoretical and experimental values of the thermal pressurisation coefficients Ʌ (MPa/ºC) for different geomaterials. The evaluation of the coefficient is usually performed by back-analysis of in situ or laboratory tests [11][12][13][14][15] or directly determined by laboratory experiments [8,10,16,17].…”

Section: Introductionmentioning

confidence: 99%

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Coupled thermo-hydro-mechanical behaviour of a deep clay

Romero

Baelen

2019

E3S Web Conf.

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An experimental study on Ypresian clays –one of the potential deep formations in Belgium for the geological disposal of heat-emitting radioactive waste– was undertaken to systematically study its thermal properties and coupled hydro-mechanical response during fast heating pulse tests. An accurate characterisation of the thermal properties is required for assessing the near-field perturbations around disposal galleries that the sedimentary host rock formation will undergo. A new experimental cell adapted to apply the high in situ stresses and with thermal flux sensors was used to directly measure the thermal conductivity at different sample orientations (heat flux orthogonal and parallel to bedding planes). A clear influence of the degree of saturation – despite being close to saturation – and anisotropic features on thermal conductivity have been detected. The study was complemented by performing fast heating pulse tests under constant volume on a new and fully-instrumented axisymmetric cell. The cell allowed recording the pore pressure build-up and dissipation along a heating pulse and under water-undrained conditions.

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Section: Results and Interpretationmentioning

confidence: 83%

Section: Introductionmentioning

confidence: 99%

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Coupled thermo-hydro-mechanical behaviour of a deep clay

Romero

Baelen

2019

E3S Web Conf.

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“…The parameter h is somewhat lower compared to the value reported for Boom Clay in [13][14][15] (h = 24 Wm -2 K -1 ), due to the fact that the setup with Boom Clay involved a more conductive still water bath to control the temperature at the boundaries of the heating cell.…”

Section: Numerical Simulations Boundary Conditions and Back-analysismentioning

confidence: 69%

Studying the thermal conductivity of a deep Eocene clay formation: Direct measurements vs back-analysis results

Romero

Lima

et al. 2016

Geomechanics for Energy and the Environment

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“…Two well-preserved Ycs core samples retrieved at different depths at Kallo (Belgium) and belonging to distinct lithological units were tested (see Table 1). Both slightly overconsolidated samples (Yield Stress Ratios of Ycs between 1.2 and 1.8, [1,2,3]) presented high initial matric suctions induced on deep water-undrained sampling. Consequently, the first stage of the well-planned test protocol consisted of loading at constant water content to bring the samples to the large in situ stresses and diminish the induced matric suction.…”

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confidence: 95%

Thermo-hydro-mechanical behaviour of a deep plastic clay formation

Sau,

Romero,

Van Baelen

2023

SEG

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Several applications which are framed in the energy geotechnics field, particularly the design of energy geo-structures, energy geo-storage, enhanced geothermal energy systems and radioactive waste disposal, require a thorough thermo-hydro-mechanical (THM) characterisation of their host soil/rock formation. The present study comes up from the need to investigate the THM behaviour of deep Ypresian clays (Ycs, 300 to 400 m below ground) since they are one of Belgium’s potential host rock formations for deep geological disposal of heat-emitting and long-lived radioactive waste. The impact of temperature on the hydro-mechanical response of deep clays has been extensively tackled for the last four decades. Nevertheless, to the authors’ knowledge, the study of the evolution of radial stresses during drained thermal paths under oedometer conditions has never been addressed. Such information would allow for drawing a better-defined stress state while accurately measuring volume changes. To this aim, the present study used a newly designed and fully instrumented temperature-controlled oedometer cell [3] combined with well-planned test protocols. The local instrumentation consisted of a pore pressure transducer embedded in the soil 3 mm from the bottom boundary, thermocouples at various positions and radial displacement transducers with a localised thin-wall system to estimate radial stress. Two well-preserved Ycs core samples retrieved at different depths at Kallo (Belgium) and belonging to distinct lithological units were tested (see Table 1). Both slightly overconsolidated samples (Yield Stress Ratios of Ycs between 1.2 and 1.8, [1, 2, 3]) presented high initial matric suctions induced on deep water-undrained sampling. Consequently, the first stage of the well-planned test protocol consisted of loading at constant water content to bring the samples to the large in situ stresses and diminish the induced matric suction. The remaining matric suction was then reduced by soaking with synthetic water equivalent to in situ. Afterwards, drained loading and unloading paths were followed to attain different vertical effective stresses at varying overconsolidation ratios (OCRs) before performing the main research goal of drained thermal paths. The heating-cooling (H-C) cycles consisted of slowly stepwise increase/decrease in temperature (steps of 10ºC) with intermediate stabilising periods of around 15 hours controlled by the embedded pore pressure transducer. Figure 1 depicts the vertical deformation in terms of the mean effective stress (p’) beyond in situ stress. Changes in radial stresses ruled the variations in p’ during heating-cooling cycles since the vertical effective stress was kept constant during non-isothermal paths. At a slightly overconsolidated (OC) state (Core-48), the drained ‘1st H-C’ cycle showed a quasi-reversible response in volume changes and radial stresses. At OC state (OCR=2) on Core-103 (‘2nd H-C’), the response was reversible. However, the induced volume change in normally consolidated (NC) states was not reversible with a contractive response dependent on the stress level. Therefore, the nature of the thermal-induced volume changes aligned with the behaviour observed on other plastic clays. Nevertheless, the stress dependence of the contractive response at NC state differed from the observations made by [4] on NC Boom Clay -the other poorly indurated clay considered as potential host rock in Belgium. As observed in ‘2nd H-C’ (NC conditions) on Core-48, a reduction of the radial effective stress was only recorded at temperatures higher than 70°C. In contrast, the radial effective stress systematically increased on heating at values < 70°C, tending the sample to lower deviatoric stress. This phenomenon might be associated with some change in the soil structure on heating that tends to a more isotropic stress state despite the oedometer condition. A clear transition between the elastic and elastoplastic domains was detected during the subsequent loading after each H-C cycle at NC states. Finally, the study included a thermo-mechanical elastoplastic interpretation: thermal expansion coefficients dependent on temperature and mean effective stress in the elastic domain and thermal softening function on post-yield drained heating.

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Coupled thermo-hydraulic pulse tests on two reference Belgian clay formations

Cited by 3 publications

References 1 publication

Coupled thermo-hydro-mechanical behaviour of a deep clay

Coupled thermo-hydro-mechanical behaviour of a deep clay

Studying the thermal conductivity of a deep Eocene clay formation: Direct measurements vs back-analysis results

Thermo-hydro-mechanical behaviour of a deep plastic clay formation

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