CRII: III: RUI: Multiphysics Modeling of Slope Stability in Post-Wildfire Environment

This award is funded in whole or in part under the American Rescue Plan Act of 2021 (Public Law 117-2).

Post-wildfire landslides and debris flows in recent years in the Western U.S. have become more frequent and led to numerous fatalities and large economic costs. The increase in landslide susceptibility in post-wildfire environment has been attributed to the increases in soil moisture and reduction of covering vegetation and root anchoring effect. The post-wildfire hillslope stabilization and rehabilitation methods are strongly relying on the knowledge of the engineering behaviors of the wildfire-burnt soil and the effect of post-wildfire environmental factors (e.g., heating-cooling and wetting-drying cycles).

However, the transitioning mechanisms from increasing soil movement to catastrophic landslide, along with the engineering characteristics of wildfire-burnt soil, remain unexplored. There is currently no readily available approach or framework to evaluate the wildfire-burnt slope stability or soil properties. This project seeks to serve the national interest by developing a multiphysics and multiscale numerical framework to analyze the engineering properties of wildfire-burnt soil under extreme conditions during and after a wildfire, thus informing our strategies for slope stabilization and remediation.

Expected project’s outcomes, such as the physics-based models, multiphysics coupling algorithms, and decision-supporting numerical data, will promote the fundamental understanding of the multiphase granular flow and renovate the technology in wildfire-burnt slope stabilization. This project will also provide a multidisciplinary learning platform through project-based challenging activities to leverage a greater awareness amongst the engineering students about the effectiveness of numerical modeling in addressing engineering challenges related to sustainable and energy viable society.

The main objective of this project is to quantify the fundamental physics that govern the mechanical and hydrologic soil behaviors and therefore slope stability in post-wildfire environments. The approach to achieve the initiative will combine analysis and numerical simulations. Towards this end, the research team will (1) empirically identify the wildfire impacts on soil erosion, including reduction of root anchoring effect and subsurface seepage flow; (2) analytically evaluate the fundamental physics during and after the wildfire, including the effect of severe temperature gradient and wetting-drying cycles on the soil fabric; and (3) numerically model the macro-scale slope stability under various combinations of micro-parameters and environmental conditions.

The stability of wildfire-burnt slopes will, for the first time, be evaluated through physics-based correlations that are informed by the particle-scale measurements from the numerical models. The project puts forward an innovative cross-disciplinary multiphysics research that will advance our fundamental understanding of multi-phase wildfire-burnt debris flow and promote insights into the correlations between micro-scale physicochemical forces and macro-scale mechanical wildfire-burnt soil behaviors.

The combination of empirical, analytical, and numerical analyses provides a powerful range of interdisciplinary tools for understanding the effect of coupled physical-thermal-mechanical-hydrologic process on the soil engineering properties.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.