Constitutive Relationships for Elastic Deformation of Clay Rock: Data Analysis

• Published in: Rock mechanics and rock engineering Vol. 44; no. 4; pp. 463 - 468
• Main Authors: Liu, H. H., Rutqvist, J., Birkholzer, J. T.
• Format: Journal Article
• Language: English
• Published: Vienna Springer Vienna 01.07.2011; Springer; Springer Nature B.V
• Subjects: Applied sciences; ARGILLITE; Buildings. Public works; Civil Engineering; Clay; Clay (material); CLAYS; CONFINEMENT; Constitutive relationships; DATA ANALYSIS; DEFORMATION; Earth and Environmental Science; Earth Sciences; Elastic deformation; ENVIRONMENTAL SCIENCES; EVALUATION; Exact sciences and technology; FRACTURES; Geophysics/Geodesy; GEOSCIENCES; Geotechnics; Heterogeneity; MANAGEMENT OF RADIOACTIVE WASTES, AND NON-RADIOACTIVE WASTES FROM NUCLEAR FACILITIES; Mechanical properties; OPALINUS CLAY; Original Paper; RADIOACTIVE WASTES; RADIOISOTOPES; Repositories; Rock; Rock deformation; Rocks; SIMULATION; Soil investigations. Testing; Strain; STRAINS; Strength of materials (elasticity, plasticity, buckling, etc.); Stress analysis; Structural analysis. Stresses; SWELLING; TRANSPORT; WATER; Coupled processes; Constitutive model; Clay rock; Constitutive equation; Clay; Data analysis; Argillaceous rocks; Site analysis; Stress strain relation; Elastic deformation; Modeling; Water permeability; Microcracking; Comparative study
• ISSN: 0723-2632; 1434-453X
• DOI: 10.1007/s00603-010-0131-4

Geological repositories have been considered a feasible option worldwide for storing high-level nuclear waste. Clay rock is one of the rock types under consideration for such purposes, because of its favorable features to prevent radionuclide transport from the repository. Coupled hydromechanical processes have an important impact on the performance of a clay repository, and establishing constitutive relationships for modeling such processes are essential. In this study, we propose several constitutive relationships for elastic deformation in indurated clay rocks based on three recently developed concepts. First, when applying Hooke’s law in clay rocks, true strain (rock volume change divided by the current rock volume), rather than engineering strain (rock volume change divided by unstressed rock volume), should be used, except when the degree of deformation is very small. In the latter case, the two strains will be practically identical. Second, because of its inherent heterogeneity, clay rock can be divided into two parts, a hard part and a soft part, with the hard part subject to a relatively small degree of deformation compared with the soft part. Third, for swelling rock like clay, effective stress needs to be generalized to include an additional term resulting from the swelling process. To evaluate our theoretical development, we analyze uniaxial test data for core samples of Opalinus clay and laboratory measurements of single fractures within macro-cracked Callovo-Oxfordian argillite samples subject to both confinement and water reduced swelling. The results from this evaluation indicate that our constitutive relationships can adequately represent the data and explain the related observations.