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Inducing tensile failure of claystone through thermal pressurization in a novel triaxial device
Geophysics · Submitted 18 Mar 2022
abstract compiled · 2026-09-23 · no language-model review
The authors' main claim The failure happened at average axial effective tensile stresses around 3.0 MPa.
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The paper's own sentences, arranged. Each label is drawn from a closed vocabulary; the number beside it is the probability the classifier gave that label. Numbers in the tables are the authors', checked by code. No sentence in this record was written by a model.
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The abstract, sentence by sentence
Complex coupled thermo-hydromechanical (THM) loading paths are expected to occur in clay rocks which serve as host formations for geological radioactive waste repositories. Exothermic waste packages heat the rock, causing thermal strains and temperature induced pore pressure build-up. The drifts are designed in such a way as to limit these effects. One has to anticipate failure and fracturing of the material, should pore pressures exceed the tensile resistance of the rock. To characterise the behaviour of the Callovo-Oxfordian claystone (COx) under effective tension and to quantify the tensile failure criterion, a laboratory program is carried out in this work. THM loading paths which correspond to the expected in situ conditions are recreated in the laboratory. To this end, a special triaxial system was developed, which allows the independent control of radial and axial stresses, as well as of pore pressure and temperature of rock specimens. More importantly, the device allows one to maintain axial effective tension on a specimen. Saturated cylindrical claystone specimens were tested in undrained conditions under constrained lateral deformation and under nearly constant axial stress. The specimens were heated until the induced pore pressures created effective tensile stresses and ultimately fractured the material. The failure happened at average axial effective tensile stresses around 3.0 MPa. Fracturing under different lateral total stresses allows one to describe the failure with a Hoek-Brown or Fairhurst's generalized Griffith criterion. Measured axial extension strains are analysed based on a transversely isotropic thermo-poroelastic constitutive model, which is able to satisfactorily reproduce the observed behaviour.
background contribution method result interpretation main claim
| # | sentence | role | the authors' own work | states the main conclusion | strength |
|---|---|---|---|---|---|
| s0 | Complex coupled thermo-hydromechanical (THM) loading paths are expected to occur in clay rocks which serve as host formations for geological radioactive waste repositories. | background 1.00 | 0.05 | 0.02 | hedged possibility 0.88 |
| s1 | Exothermic waste packages heat the rock, causing thermal strains and temperature induced pore pressure build-up. | background 1.00 | 0.06 | 0.02 | asserted 1.00 |
| s2 | The drifts are designed in such a way as to limit these effects. | background 1.00 | 0.06 | 0.02 | asserted 0.99 |
| s3 | One has to anticipate failure and fracturing of the material, should pore pressures exceed the tensile resistance of the rock. | background 0.95 | 0.05 | 0.06 | hedged possibility 0.77 |
| s4 | To characterise the behaviour of the Callovo-Oxfordian claystone (COx) under effective tension and to quantify the tensile failure criterion, a laboratory program is carried out in this work. | contribution 1.00 | 0.93 | 0.04 | asserted 0.96 |
| s5 | THM loading paths which correspond to the expected in situ conditions are recreated in the laboratory. | method 0.83 | 0.82 | 0.03 | asserted 0.98 |
| s6 | To this end, a special triaxial system was developed, which allows the independent control of radial and axial stresses, as well as of pore pressure and temperature of rock specimens. | method 0.97 | 0.91 | 0.03 | asserted 1.00 |
| s7 | More importantly, the device allows one to maintain axial effective tension on a specimen. | method 0.81 | 0.74 | 0.04 | asserted 1.00 |
| s8 | Saturated cylindrical claystone specimens were tested in undrained conditions under constrained lateral deformation and under nearly constant axial stress. | method 1.00 | 0.95 | 0.03 | asserted 1.00 |
| s9 | The specimens were heated until the induced pore pressures created effective tensile stresses and ultimately fractured the material. | method 0.95 | 0.95 | 0.14 | asserted 1.00 |
| s10 | The failure happened at average axial effective tensile stresses around 3.0 MPa. | result 1.00 | 0.96 | 0.43 | asserted 1.00 |
| s11 | Fracturing under different lateral total stresses allows one to describe the failure with a Hoek-Brown or Fairhurst's generalized Griffith criterion. | interpretation 0.57 | 0.85 | 0.25 | asserted 0.81 |
| s12 | Measured axial extension strains are analysed based on a transversely isotropic thermo-poroelastic constitutive model, which is able to satisfactorily reproduce the observed behaviour. | method 0.54 | 0.91 | 0.13 | asserted 0.98 |
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Original abstract
Complex coupled thermo-hydromechanical (THM) loading paths are expected to occur in clay rocks which serve as host formations for geological radioactive waste repositories. Exothermic waste packages heat the rock, causing thermal strains and temperature induced pore pressure build-up. The drifts are designed in such a way as to limit these effects. One has to anticipate failure and fracturing of the material, should pore pressures exceed the tensile resistance of the rock. To characterise the behaviour of the Callovo-Oxfordian claystone (COx) under effective tension and to quantify the tensile failure criterion, a laboratory program is carried out in this work. THM loading paths which correspond to the expected in situ conditions are recreated in the laboratory. To this end, a special triaxial system was developed, which allows the independent control of radial and axial stresses, as well as of pore pressure and temperature of rock specimens. More importantly, the device allows one to maintain axial effective tension on a specimen. Saturated cylindrical claystone specimens were tested in undrained conditions under constrained lateral deformation and under nearly constant axial stress. The specimens were heated until the induced pore pressures created effective tensile stresses and ultimately fractured the material. The failure happened at average axial effective tensile stresses around 3.0 MPa. Fracturing under different lateral total stresses allows one to describe the failure with a Hoek-Brown or Fairhurst's generalized Griffith criterion. Measured axial extension strains are analysed based on a transversely isotropic thermo-poroelastic constitutive model, which is able to satisfactorily reproduce the observed behaviour.
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