Unravelling Champlain Clay Subsidence: Integrating Persistent Scatterer InSAR and Finite-Element Modeling

Excessive decline in pore pressure in fine-grained soils can lead to substantial land subsidence, a phenomenon increasingly observed worldwide amid the water crisis linked to climate change. The presence of soft and sensitive Champlain clays in the Saint Lawrence River Valley in Southeastern Canada makes this region prone to soil deformation. This article investigates vertical ground movements at a designated test site through the integration of numerical modeling and the persistent scatterer InSAR (PSI) technique. A model was developed using the finite-element method (FEM) and Biot's theory of poroelasticity. This model predicts soil settlement and heave by analyzing pore pressure data from the bedrock and fractured clay layers as well as temperature measurements from a study site in Sainte-Marthe, Quebec. The model is tailored to capture deformations in distinct layers, distinguishing between a more actively hydraulically influenced superficial top layer and a deeper, intact clay layer. Subsequently, vertical displacements were computed at the location of the study site and on a broader scale using the PSI technique, employing SARPROZ software with linear and nonlinear approaches. Results showcased a satisfactory correlation between FEM simulations and PSI estimates, revealing a seasonal trend of displacement with a maximum range of 15 mm. Over a 30 month span, the FEM model and nonlinear PSI approach estimated subsidence reaching up to 55 mm. Notably, the nonlinear PSI method demonstrated superior efficacy in identifying nonlinear soil displacements, displaying a displacement velocity of -9 mm=year compared with the -8 mm=year estimated by the FEM approach.