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

该奖项全部或部分由《2021年美国救援计划法案》（公法117-2）资助。近年来，美国西部野火后的山体滑坡和泥石流变得更加频繁，造成了大量人员死亡和巨大的经济损失。山火后环境中滑坡易感性的增加与土壤水分的增加、覆盖植被的减少和根系锚定效应有关。野火后的边坡稳定与恢复方法在很大程度上依赖于野火后土壤的工程行为和环境因素（如加热-冷却和干湿循环）的影响。然而，从增加的土壤运动到灾难性滑坡的过渡机制，以及野火燃烧土壤的工程特性，仍未被探索。目前还没有现成的方法或框架来评估野火烧毁的边坡稳定性或土壤性质。该项目旨在通过开发多物理场和多尺度数值框架来分析野火期间和之后极端条件下野火烧伤土壤的工程特性，从而为我们的边坡稳定和修复策略提供信息，从而为国家利益服务。预期的项目成果，如基于物理的模型、多物理场耦合算法和支持决策的数值数据，将促进对多相颗粒流的基本理解，并革新野火边坡稳定技术。该项目还将通过基于项目的挑战性活动提供一个多学科学习平台，以提高工科学生对数值建模在解决与可持续和能源可行社会相关的工程挑战方面的有效性的认识。该项目的主要目标是量化野火后环境中控制机械和水文土壤行为以及边坡稳定性的基本物理。实现这一倡议的方法将结合分析和数值模拟。为此，研究团队将(1)实证识别野火对土壤侵蚀的影响，包括减少根系锚定效应和地下渗流；(2)分析评价了山火发生时和发生后的基本物理特性，包括剧烈的温度梯度和干湿循环对土壤结构的影响；(3)对不同微观参数和环境条件组合下的宏观尺度边坡稳定性进行数值模拟。野火烧毁斜坡的稳定性将首次通过基于物理的相关性进行评估，这种相关性由数值模型的颗粒尺度测量提供信息。该项目提出了一个创新的跨学科多物理场研究，将促进我们对多相野火泥石流的基本认识，并促进对微观尺度物理化学力与宏观尺度野火土壤力学行为之间相关性的认识。经验，分析和数值分析的结合为理解物理-热-机械-水文耦合过程对土壤工程性质的影响提供了强大的跨学科工具。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

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.