Development and application of new constitutive models to simulate the hydraulic-mechanical behaviour of unsaturated swelling clay
Bibliographic record
Abstract
Unsaturated swelling clays are used in engineered barriers for waste disposal facilities due to their self-sealing ability and low hydraulic conductivity. The characterization of unsaturated clay behaviour is required for design of these barriers. In recent years, several small-scale laboratory and full-scale field tests have been conducted to characterize the mechanical and hydraulic behaviour of the unsaturated swelling clay. This focus of the present study is towards the development of constitutive models to simulate hydraulic and mechanical behaviour of precompacted unsaturated swelling clay, called the bentonite-sand buffer (BSB) material. Development, calibration, implementation, and application of the proposed constitutive models form the scope of the study. The results of laboratory triaxial tests with controlled suction and suction measurements are used to calibrate the constitutive models presented. An algorithm, called the PEM (Parameter Evaluation Method), which is useful to estimate constitutive model parameters and evaluate the performance of constitutive models is proposed. This algorithm has been used to estimate the parameters of two elasto-plastic constitutive models (i.e., the BBM (Alonso et al. 1990) and the BGM (Blatz and Graham 2003)) based on the laboratory tests results on the BSB material. New 3-dimensional porosity-dependent permeability model (kwn) and water retention surface (WRS) are developed in this study. The mathematical formulations of these models using parameters calibrated with laboratory tests conducted on the BSB material are provided. Implementation algorithms of the BBM, the BGM, the kwn, and the WRS in 2-phase flow hydraulic-mechanical (H-M) analysis using a 2D-finite difference method are also provided . Three combinations of hydraulic and mechanical constitutive models (linear elastic model, BGM, vanGenuchten (1980) and kwn models) are used to simulate small-scale infiltration processes in the BSB material. Two types of tests, constant volume (CV) and constant mean stress (CMS) tests are simulated using 2D-finite difference H-M analysis. The full-scale isothermal test (ITT) of AECL is modelled using 3 combinations of H-M constitutive models. The ITT experiment comprises of buffer, rock, and concrete materials. The selected combinations of H-M constitutive models are used in three types of analyses: buffer-only (BO); buffer-rock with 20x30m domain (BR); and time-dependent boundary conditions (BCt). The results of the study show that the applications of the elasto-plastic mechanical constitutive models and porosity-dependent permeability (kwn) model are improvements over existing constitutive models to model this class of problem. The rock properties and applied boundary conditions are significant in modelling the ITT experiment. The application of the time-dependent boundary condition can reduce the uncertainty of the rock properties and boundary conditions within the rock, so that it improves the model ability to simulate the hydraulic-mechanical behaviour of unsaturated swelling clay.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 0.001 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.001 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".