Numerical modelling and InSAR monitoring of settlement in \nChamplain clays
Bibliographic record
Abstract
The presence of Champlain clay deposits in vast areas of eastern Canada brings a higher probability of geotechnical hazards in this region. Soil settlement is one of the geotechnical hazards that is believed to be strongly correlated to the presence of Champlain clays. High compressibility and significant soil moisture changes are two key elements involved in settlement of Champlain clays. Land subsidence in fine-grained soil is often caused by an excessive pore pressure decline. Numerical modelling of the pore pressure within clay aquitards can thus provide valuable information on the causes and progress of settlement. \n \nThe pore pressure fluctuations measured in deep aquitards are also correlated to moisture loading above it. Analyzing the pore pressure record corrected for barometric and Earth tide effects allows this correlation to be quantified. This relationship is more complex in shallow aquitards due to their stronger interactions with the surrounding environment. Seasonal fluctuations of the water table are an example of these interactions. These fluctuations induce pore pressure changes through transient flow. In the first part of this thesis, a finite-element model (FEM) was developed with COMSOL Multiphysics. The model simulates the pore pressure changes within a saturated Champlain clay aquitard using a coupled flow-deformation model. A MATLAB script was also prepared for the MATLAB LiveLink interface in COMSOL based on a series of hydrological equations. The MATLAB script iterates step-bystep on a total stress boundary conditions to replicate the pore pressure time series obtained in the field. These data were obtained from the Sainte-Marthe test site near Montreal, Canada. \n \nThe second part of this thesis is dedicated to InSAR monitoring and numerical modelling of settlement. It investigates the vertical ground movements between May 2017 and December 2019 on the test site using numerical modelling and the Persistent Scatterer InSAR (PSI) technique. In this regard, a model based on the finite element method (FEM) and Biot's poroelasticity theory was developed. The model estimates soil settlement and expansion using pore pressure measurements in the bedrock and fractured clay layer, and temperature obtained from a study site in Sainte-Marthe, Quebec. The model is capable of addressing the deformation separately in a hydraulically more active superficial top layer and deeper intact clay layer. To monitor the settlement at the study site, vertical displacements were calculated at a larger scale in the Vaudreuil-Soulanges region with the PSI technique using SARPROZ with linear and non-linear approaches. \n \nThe last part of this thesis deals with the monitoring of settlement on Montreal Island between April 2016 and April 2022. The displacement velocity was monitored using the PSI method and a linear technique all over the Montreal Island. The aim of this monitoring was to detect the main areas with large settlements on Montreal Island. The results in this thesis can be grouped in three parts. The results for the first part of this thesis dealt with numerical modelling of the pore pressure changes. These results showed that the model can reproduce the historical pore pressure time series reasonably well. Implementation of the MATLAB script could significantly improve the optimization results. Concerning the numerical modelling of settlement in the second part of the thesis, the results show a reasonable agreement between the FEM simulations and PSI estimates. A seasonal trend of displacement with a maximum range of 15 mm was estimated. Subsidence as large as 55 mm was estimated by the FEM model and non-linear PSI approach over a period of 30 months. Non-linear PSI could detect the non-linear displacement of the soil more effectively. The displacement velocity was -9 mm/year for the non-linear method compared to -8 mm/year for the FEM estimation. The long-term monitoring of the settlement on Montreal Island revealed that serious settlements up to -10 mm/year are in progress in certain areas of the Montreal Island. The continuous progress of settlement in this region might be induced by a decrease in the soil water moisture associated with the effect of climate change.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 0.001 |
| Meta-epidemiology (narrow) | 0.001 | 0.001 |
| Meta-epidemiology (broad) | 0.002 | 0.000 |
| Bibliometrics | 0.000 | 0.002 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.002 | 0.002 |
| Research integrity | 0.003 | 0.003 |
| Insufficient payload (model declined to judge) | 0.002 | 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; both teacher heads agree on what is shown here.
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".