16-05-2022 | Original Paper
In-situ Shear Modulus Determination by Pressuremeter Tests in Opalinus Clay and Reconciliation with Laboratory Tests
Published in: Rock Mechanics and Rock Engineering | Issue 8/2022
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Abstract
Highlights
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High-quality pressuremeter tests are performed in Opalinus Clay to assess its in-situ static elastic stiffness using the unloading steps at multiple expansion pressure levels.
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Assuming axisymmetric borehole deformation, the shear modulus determined in the borehole oriented parallel to bedding is significantly lower than that determined in the borehole oriented perpendicular to bedding.
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The measured shear modulus can also be affected by the rock mass disturbance and the local fractures at the test interval.
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The interpreted secant shear modulus is nonlinearly dependent on the small strain increment during unloading, which can be characterized by a power-law stress-strain relationship.
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An agreement on the measured shear moduli (parallel to bedding) can be established between the pressuremeter and laboratory triaxial tests on intact Opalinus Clay when the strain dependency of the modulus is considered for both tests.
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This study presents a framework for bridging the elastic stiffness measurements of weak argillaceous rocks using high-quality laboratory and in-situ tests.