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

当地球物质沿着剪切带崩塌后迅速下坡时，就会发生山体滑坡。泥石流与滑坡的不同之处在于被动员的物质普遍存在的流体状变形。山体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，关于水文驱动的斜坡破坏的研究已经取得了很大的进展，但在基于物理的三维流体流动和变饱和土壤中的水文驱动的斜坡失稳方面还没有进行重要的研究。该奖项资助跨学科研究，重点是在集水范围内对陡峭山坡的水文响应/斜坡稳定过程进行基于物理的表征。该模型将在可变饱和土壤中将固体变形与流体流动过程相结合，并量化地下和地表连续体之间的水交换。这使我们能够更好地了解地表径流、蒸散和渗透对变饱和坡面内饱和度、有效应力和变形模式的时空变化的影响。耦合模型将用库斯湾实验流域(CB1)的全面和详尽的数据以及最近使用综合水文模型(INHM)对同一流域进行的模拟的数值结果进行检验。这项研究还将利用最近开发的稳定的低阶有限元近似格式，对固体位移场和孔隙压力场采用等阶内插。1996年11月，高度仪器化的CB1斜坡以大型泥石流的形式失败，从而提供了大量数据来比较模型预测。研究小组将结合斯坦福大学提供的岩土工程、计算地质力学和定量水文地貌学的专业知识，开发和测试基于物理的斜坡破坏起始模型。根据PI的知识，目前在文献中还没有以定量的方式解决可变饱和度的影响的边坡破坏起始模型。我们相信，有限元方法已经达到了如此高级的阶段，现在它不仅可以处理复杂的几何形状，而且还可以处理可变饱和度的影响。这项研究的另一个智力价值在于有巨大的机会用现有的数据集来测试和验证所提出的数学方法。CB1数据集允许在具有复杂地形和可变饱和度的大型斜坡上进行模型测试和验证。CB1高质量水文和岩土数据的可获得性将有助于约束问题的参数，从而为更好地了解控制斜坡失稳的重要过程提供了巨大的机会。这项研究及时地促进了对系统中控制斜坡失稳过程的更好理解，该系统由近地表水文和土壤组成性质的严格表征驱动。模拟工作将有效地展示基于物理的斜坡稳定性模型的实用性和/或局限性，这些模型不如这里针对类似CB1的野外条件开发的模型那么全面。拟议的研究还将利用计算流体动力学的进展，将其应用于岩土工程和地球科学问题。两家私人投资机构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一项目。这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方面得到证实的记录中收集到。

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.