Development of a viscoelastoplastic model for a bedded argillaceous rock from laboratory triaxial tests

Abstract

Argillaceous rocks are candidate host and (or) cap formations for the geological disposal of nuclear wastes in many countries, including Canada, France, and Switzerland. The understanding of the long-term mechanical behaviour of such rocks is an essential requirement for the assessment of their performance as a barrier against radionuclide migration. The French Institute for Radiological Protection and Nuclear Safety (IRSN) operates an Underground Research Laboratory (URL) in Tournemire, France, in a rock formation known as the Tournemire shale. Many types of experiments are conducted at the Tournemire URL to better understand the physical and chemical behaviour of this shale and its interaction with seal materials intended to be used in the geological disposal of radioactive wastes. The Canadian Nuclear Safety Commission (CNSC) collaborates with the IRSN and CanmetMINING laboratories to perform experimental and theoretical research on the mechanical behaviour of the Tournemire shale. Using data from creep tests, and monotonic and cyclic triaxial tests performed at CanmetMINING Laboratories, we developed constitutive relationships for the mechanical behaviour of the Tournemire shale. The model is based on the theory of plasticity, and takes into consideration the inherent anisotropy due to the existence of bedding planes, hardening behaviour before the peak strength, and viscosity.Key words: shale, viscoelastoplasticity, anisotropy, triaxial test, geological disposal.Résumé : Dans de nombreux pays comme le Canada, la France ou la Suisse, les roches argileuses sont des formations candidates pour le stockage géologique des déchets nucléaires. La compréhension du comportement mécanique à long terme de ces roches est une condition essentielle pour l'évaluation de leur performance comme une barrière contre la migration des radionucléides. Mots-clés : schiste, viscoelastoplasticité, anisotropie, essai triaxial, stockage géologique.

Impacts of Disk Rock Sample Geometric Dimensions on Shear Fracture Behavior in a Punch Shear Test

“…The PST is applicable for high strength solids, minimizes the bending stress on the samples, and facilitates sample preparation [17,18]. Thus, other testing methods, such as the punch through shear test which uses a rock disk sample with two circular notches, was proposed based on the PST to determine shear mechanical parameters [19][20][21]. [22] Rock sample dimensions in laboratory tests significantly impact the test result.…”

Long‐Term Settlement of High Concrete‐Face Rockfill Dam by Field Monitoring and Numerical Simulation

“…eoretical models mainly use elastic elements (linear springs), viscous elements (Newton's stick pots), and plastic elements (friction parts) to form series and parallel connections to describe time-dependent stress-strain relationship of rockfill materials. Based on the combination and expansion of the above three elements, a variety of theoretical models for evaluating creep behavior of rockfill materials have been proposed [45,46], such as Merchant model, viscoelastic model, elastic-viscoplastic model, elastoplastic model, and Hardening Soil Creep (HSC) model [40,[47][48][49][50][51][52]. eoretical models are supported by rigorous mathematical theory, which is very important for investigating the mechanical characteristics of rockfill materials.…”

A Creep Damage Constitutive Model for a Rock Mass with Nonpersistent Joints under Uniaxial Compression

“…As is known to all, these two different scale flaws both affect the jointed rock mass strength and deformability. Now because of its complexity, the existing studies on the creep mechanical behavior mainly focused on the rock element involving theoretical, experimental, and numerical methods [5][6][7]. Especially, the study on the creep constitutive model for the rock element is one of the most fundamental and important issues in the rock mass rheological mechanics which attracts much attention [8][9][10].…”

“…rough the laboratory experiment on the sandstone samples with nonpersistent joints subjected to shear creep, Wu et al [22] developed a new creep model considering the effect of joint length on the rock time-dependent behavior. Li et al [6] developed a damage rheology model for jointed rock masses in which the damage caused by the joints to the rock mass is described with a second-order tensor.…”