复杂地形泥石流动力过程物理模型及数值解析研究

Debris-flow dynamic behavior is a key process during the initiation and development of debris-flow hazards. Analytical study using numerical simulation method is a means of solution for debris-flow dynamic behavior. Up-to-date studies indicate that this kind of dynamic behavior is significantly influenced by the initiation of the loose material on the slope, and the basal entrainment along the path. In this context, the scientific challenge for a well-balanced numerical model considering the process-based physical model of the debris flow dynamic behavior is consequently highlighted at the current stage. As such, this project aims to solve the above issues on the basis of our previous research. Data collection work is firstly conducted including in-situ surveys, topography measurement by 3D-laser scanning, as well as flume experiments. These data are deeply analyzed to know the initiation mechanism of the debris mass on the slope of the source area, and to reveal the essential factors and their critical condition controlling the basal entrainment process. The physical understanding of mass initiation and basal entrainment helps to estimate the hazard magnitude and its temporal and spatial variation during the debris-flow process. The proposed physical model is subsequently incorporated into the numerical model in our previous studies. By addressing the optimization issue of the dry-wet boundary over complex topography, a well-balanced numerical model will be developed, which is featured to provide a stable, high-efficiency, and visualized simulation on the debris-flow dynamic behavior. This project at one hand makes a benefit supplement for the theory of debris-flow dynamics from an academic viewpoint. On the other hand, focusing on the pressing need of practical work, a user-friendly software with pre- and post-processors is provided, which will namely be a useful tool for supporting the debris-flow mitigation work.

泥石流动力过程是泥石流灾害发生与发展的中心环节，采用数值模拟方法对其进行解析具有重要意义。最新研究表明，储供物源起动与沿途侵蚀补给对泥石流动力过程存在显著影响，如何构建考虑相应物理机制的数值模型，并解决复杂地形下的计算稳定性难题已成为目前研究的热点。为此，本项目依托前期研究积累，通过现场调查、三维地形激光扫描测量、模型实验等手段，探讨泥石流易发坡面储供物源失稳起动的机制机理、揭示侵蚀过程关键因素及临界状态，以明确泥石流初始起动规模及其随侵蚀过程发展的时程演化；同时在已建立的数值模型框架内整合动力过程物理模型，重点解决沟道复杂地形单元界面的优化处理问题，最终实现对泥石流动力过程稳定、高效及可视化的模拟与解析。其特色在于，不仅在学术层面上对泥石流动力学理论体系进行有益补充，而且紧密围绕泥石流灾害防灾工作实际需求开发对应程序，强调成果在工程应用上的延伸，为泥石流灾害预测与合理防治提供了初步依据。

泥石流作用下沟床堆积物侵蚀过程分析及模拟一直是国内外研究非常重视但仍待解决的关键科学问题。这一问题有其独特性，即泥石流沟床侵蚀属流固耦合问题，机理尚不明确，加之泥石流流变特性及动力特征复杂，传统二维数值模型在模拟强侵蚀泥石流动力过程复杂特性的问题上存在局限。.为此，本项目主要围绕复杂地形泥石流动力过程物理模型及数值解析开展研究，构建了土体强度及灾害动力特征等信息不完备条件下的沟床堆积物侵蚀模型，发展了基于HBP非线性本构的泥石流物源起动小剪应变的SPH数值计算框架，并将侵蚀模型与数值计算框架进行了集成，形成了考虑沿程侵蚀冲刷的泥石流动力过程三维数值模型。项目研究期间取得如下创新性成果：.（1）构建了沟床堆积物-泥石流流体耦合模型，推导了基于动量守恒原理的泥石流作用下沟床松散堆积物的侵蚀速率计算模型，实现了在沟床堆积物土体强度及孔隙水压力动态不确定性变化等信息不完备条件下的侵蚀深度计算；.（2）分析了传统二维、三维泥石流数值模型中常用的Bingham及Cross流变模型在泥石流物源起动小剪应变阶段的数值发散问题，引入了HBP非线性本构，基于理论推导得出了三维SPH框架下的N-S方程，并在方程中实现了HBP非线性本构模型的整合，建立了三维HBP-SPH泥石流动力过程数值模型；.（3）提出了基于表面网格的三维光滑粒子统计算法，通过该算法在HBP-SPH泥石流动力过程数值计算框架内，实现了侵蚀计算模型在SPH数值模型中的整合，构建了SC-HBP-SPH泥石流沟床堆积物侵蚀三维数值模型，解决了泥石流动力过程模拟中流态及规模逐级放大的量化计算难题。.依托上述研究成果，项目共计形成SCI论文12篇、EI论文1篇、中文核心期刊论文3篇。其中，1篇论文发表于Nature Index自然指数源刊、4篇论文发表于中科院1区TOP期刊、1篇论文入选ESI1%高被引论文及ESI0.1%热点论文。新增国家发明专利申请7项，完成了项目预期目标及指标。项目研究成果为突破泥石流侵蚀沟床三维复杂过程分析的关键问题提供了支撑。