Damage Evolution in an Underground Gallery Induced by Drying

作者：Pichler Bernhard; Cariou Sophie; Dormieux Luc^*

来源：International Journal for Multiscale Computational Engineering, 2009, 7(2): 65-89.

DOI：10.1615/intjmultcompeng.v7.i2.20

• micromechanics
• poromechanics
• microporomechanics
• homogenization
• linear poroelasticity
• fluid transport
• drying shrinkage
• crack propagation
• atomic waste
• argillite
• tunnel

We study the structural behavior of a rock mass made of argillite, from which a cylindrical underground opening was excavated. Prescribing that the relative humidity of the air within the gallery is < 100% causes the surrounding clay-containing, sedimentary rock to desaturate and to dry progressively. Because near-surface layers dry faster than the domains behind, shrinkage deformations are hindered, which promotes the cracking risk of the material. This phenomenon is studied by means of a multiscale approach which involves four separated scales of observation, including consideration of two types of rock mass porosity: (i) mesocracks inform of oblate spheroids and (ii) spherical micropores. Assuming macroscopic radial symmetry, the drying-related fluid transport problem is solved first, which results in computed fields of capillary pressure and gas pressure, covering the first 50 years after gallery excavation. These data allow for deriving the pressure fields within mesocracks and within micropores, on lower scales of observation. Homogenization based on a microporomechanics approach delivers the related macroscopic prestresses, which enter the structural analysis of the deformation behavior of the rock mass. Accompanying the structural drying analysis, the mesocrack propagation risk is continuously monitored by means of a thermodynamics-based crack propagation law. Once onset of mesocrack propagation is observed, damage evolution is modeled. This engineering combination Of a microporomechanical material model with a computational tool for macroscopic structural analysis allows for studying the expansion of a drying-related damage front that propagates-at rather small speed-into the rock mass. This effect should be dealt with carefully when planning to use such an underground gallery as a disposal site for atomic waste.

• 出版日期2009