泥石流流变特性及其传播过程的高分辨率数值模拟研究

Debris flow is a natural environmental particle-laden flow that exhibits strongly erosive power to the bed. Poor understanding of key mechanisms of rheological property of wet granular matter causes that the prediction of flow, spread and erosion process of debris flow departs a lot from what happens in the real world. The main object of this project is to study the rheological property of wet granular matter, and to develop new dynamical model for debris flow based on mechanics of wet granular matter, which is then used to understand the transport and deposition of debris flow under different conditions. Discrete element method is used to study the evolution of contact network and force chain of granular matter under shear, based on which, a multiscale method will be used to study the mechanism of both solid-liquid transition and rheology to provide a rheological constitutive law for granular flow. With the incorporation of erosive model, a mixture model for debris flow will be established, and high-resolution numerical scheme will be proposed and implemented for the conservative equations. It is then used to study the flow process of debris flow, to make a better understanding of the transport and deposit of debris flow under conditions of different granular medium, terrain parameters and bed materials. Finally, whole processes of 1-2 real debris flows will be simulated to enhance the understanding of flow and erosion behavior of debris flow in the real world.

泥石流是自然界广泛存在的一种强侵蚀含水颗粒物质流动。目前对含水颗粒物质的流变模式缺乏机理性认识，造成对泥石流的流动、铺展和侵蚀等过程的预测和实际情况差距较大。本项目重点研究含水颗粒物质的流变特性，建立以颗粒物质力学为基础的泥石流发展过程动力学模型，研究泥石流的传播距离和堆积范围。采用颗粒离散元方法分析颗粒物质在剪切作用下颗粒接触作用和力链演化的规律，以此为基础通过多尺度方法分析颗粒物质的固液转化和流变机制，并最终给出颗粒流的流变模式。考虑侵蚀模型，建立泥石流发展过程的混合物力学模型，并发展高分辨率数值算法。应用数值模型大量研究泥石流的传播和发展过程，深入认识介质特性、地形参数和床面介质特征对泥石流传播距离和堆积范围的影响。最后模拟1-2个实际泥石流的发展过程，加深对实际地形环境下泥石流流动和侵蚀规律的认识。

本项目主要围绕泥石流颗粒物质复杂介质力学行为，泥石流运动演化动力学模型和关键算法，以及工程应用开展系列的研究工作。建立了泥石流颗粒物质力学行为、流固耦合行为的离散元模拟方法，研究得到了颗粒物质变形-剪胀-强度行为、土水特征曲线以及吸应力曲线等；发展了复杂地形条件泥石流运动演化动力学模型以及高效数值计算方法，研究了复杂泥石流运动与结构物相互作用的规律；作为应用，基于关键模型和算法开发了Gava软件，研究了复杂真实地形条件工程地质尺度的大型泥石流滑坡运动演化过程，包括易贡泥石流、灵石尾矿溃坝流、白格堰塞坝。