Coupled Solid-Deformation/Fluid-Flow Simulation of Failure Initiation in Variably Saturated Slopes

当土料在沿着剪切带破裂后迅速向下移动时，就会发生滑坡。 泥石流与滑坡的区别在于流动物质的普遍的、流体状的变形。 滑坡和泥石流威胁着全世界的生命和财产。 尽管在过去的二十年里，相对于理解水文驱动的边坡失稳，已经取得了很好的进展，重要的研究还没有进行在三维物理为基础的流体流动和水文驱动的边坡失稳在饱和土壤。该奖项资助跨学科研究，重点是在集水区规模的陡坡耦合水文响应/边坡稳定性过程的物理表征。 该模型将耦合固体变形与非饱和土壤中的流体流动过程，以及量化地下和表面连续体之间的水交换。 这使我们能够更好地了解地表径流，蒸散，渗流的饱和度，有效应力和变形模式的空间和时间变化的影响，在非饱和边坡。 耦合模型将测试全面和详尽的数据从库斯湾实验集水区（CB 1），以及最近进行的模拟在同一集水区使用综合水文模型（InHM）的数值结果。 本研究也将利用最近开发的稳定的低阶有限元近似方案，采用相等的固体位移和孔隙压力场的插值阶数。 1996年11月，经过高度仪器化的CB 1斜坡发生大型泥石流，从而提供了大量数据来比较模型预测。研究团队将结合联合收割机在岩土工程、计算地质力学和定量水文地貌学方面的专业知识，在斯坦福大学开发和测试基于物理学的斜坡破坏启动模型。 据PI所知，目前文献中没有以定量方式解决可变饱和度影响的边坡破坏启动模型。 我们相信，有限元方法已经达到了这样一个先进的阶段，它现在不仅可以处理复杂的几何形状，但也可变饱和度的影响。 这项研究的另一个智力价值在于，利用现有数据集测试和验证所提出的数学方法的巨大机会。CB 1数据集允许在具有复杂地形和可变饱和度的大规模斜坡上进行模型测试和验证。 CB 1的高质量水文和岩土工程数据的可用性将有助于限制问题的参数，因此，提供了巨大的机会，以获得更好地了解控制边坡不稳定的重要过程。这项研究是一个及时的贡献，以提高对控制边坡不稳定的过程，在一个系统驱动的严格表征的近-地表水文和土壤结构特性。 模拟工作将有效地证明基于物理的边坡稳定性模型的实用性和/或局限性，该模型不如针对类似于CB 1的现场条件开发的模型全面。 拟议的研究还将利用计算流体动力学的进展应用于岩土工程和地球科学问题。 两个PI都认真致力于确保本科生和代表性不足的学生充分参与这个项目。 这一点可以从他们在斯坦福大学指导、建议、监督和毕业本科生和代表性不足的学生的良好记录中得到证明。

Landslides occur when earth material moves rapidly downhill after failing along a shear zone. Debris flows are differentiated from landslides by the pervasive, fluid-like deformation of the mobilized material. Landslides and debris flows threaten lives and property worldwide. Despite the fact that good progress has been made within the last two decades relative to understanding hydrologically-driven slope failure, important research has yet to be conducted in 3D physics-based fluid flow and hydrologically-driven slope instability in variably saturated soils. This award funds interdisciplinary research focused on a physics-based characterization of coupled hydrologic response/slope stability processes for steep hillslopes at the catchment scale. The model will couple solid deformation with fluid flow processes in variably saturated soils, as well as quantify the exchange of water between the subsurface and surface continua. This allows us to better understand the effects of surface runoff, evapotranspiration, and percolation on the spatial and temporal variations of degree of saturation, effective stress, and deformation pattern within the variably saturated slope. The coupled model will be tested with comprehensive and exhaustive data from the Coos Bay experimental catchment (CB1), as well as with the numerical results of recently conducted simulations on the same catchment using an Integrated Hydrology Model (InHM). This research will also utilize a recently developed stabilized low-order finite element approximation scheme employing equal orders of interpolation for the solid displacement and pore pressure fields. The highly instrumented CB1 slope failed as a large debris flow in November 1996, thus providing large volumes of data with which to compare the model predictions.The research team will combine expertise in geotechnical engineering, computational geomechanics, and quantitative hydrogeomorphology available at Stanford University to develop and test a physics-based model of slope failure initiation. To the knowledge of the PIs, no slope failure initiation model currently exists in the literature that addresses the effect of variable saturation in a quantitative way. We believe that the FE method has reached such an advanced stage that it can now handle not only complex geometry but also the effect of variable saturation. A further intellectual merit of this research lies in the tremendous opportunity for testing and validation of the proposed mathematical approaches with the available data set. The CB1 data set allows model testing and validation on a large-scale slope with complex topography and variable saturation. The availability of high-quality hydrological and geotechnical data for CB1 will help constrain the parameters of the problem, thus providing tremendous opportunity to gain a better understanding of the important processes controlling slope instability.The study is a timely contribution towards an improved understanding of the processes that control slope instability in a system driven by a rigorous characterization of the near-surface hydrology and soil constitutive properties. The simulation effort will effectively demonstrate the utility and/or limits of physics-based slope stability models less comprehensive than the one to be developed here for field conditions similar to CB1. The proposed research will also utilize the advances in computational fluid dynamics for application to geotechnical and geosciences problems. Both PIs are seriously committed to ensuring full involvement of undergraduate and underrepresented students in this project. This can be gleaned from their proven track record of mentoring, advising, supervising, and graduating undergraduate and underrepresented students at Stanford.