High speed granular debris flows: new paradigms and interactions in geomechanics

泥石流（又称泥石流）是一种快速滑坡，是土、岩、水以高速向山下流动的一种形式。这些自然灾害传播距离很长，对它们在流动路径上遇到的生命和基础设施构成风险。在泥石流事件期间，固体颗粒尺寸和流体分离，使得大颗粒集中在前部，导致高冲击力。这使得他们的行为既危险，物理上的复杂性，所以有几个数学和数值颗粒流理论竞争来解释他们的motion.This研究旨在提高我们的理解泥石流和冲击应力，他们可能会导致他们遇到的障碍，通过进行一系列新颖的实验室规模的测试，在2D和3D模型泥石流通道内的流动限制。在2D模型实验中，土壤和岩石将被丙烯酸颗粒取代，并且使用光弹性方法来确定单个颗粒中的力，因为材料向下流动而不考虑流体相互作用。然后将结果与当前的颗粒流理论进行比较，以确定哪种理论在颗粒运动和颗粒中引起的应力方面与结果最匹配。在3D实验中，土壤和岩石将被玻璃颗粒取代，水将被光学匹配的流体取代，这将使混合物几乎透明。然后，穿过系统的激光平面将在其中心创建流动的可视切片，使得颗粒的2D切片在高速运动期间在明亮的流体背景下看起来是暗的。通过高速摄影捕捉这种行为将能够在存在流体和远离侧壁边界效应的颗粒运动方面与3D颗粒流理论进行比较。在3D的第二系列测试中，障碍物代表流动或基础设施的结构障碍，将被放置在一个模型的玻璃和流体泥石流的路径，使其与障碍物的相互作用可以检查。以及使用更传统的技术，使用一种新的方法，全息干涉测量法将进行试验，以确定如何在结构本身的变形和应力与颗粒的影响，从模型泥石流。这种方法可以检测整个物体上非常小的变形，因此非常适合于研究多个粒子与不同形状和大小的障碍物的复杂相互作用。总体结果将是一个多个数据集，可以用来更好地模拟泥石流数值，其中包括泥石流对结构的影响和泥石流结构。人们希望，研究结果可能导致更好地设计泥石流屏障，加强和保护自然和人造环境，从而更好地保护人类生命。

Debris flows (often called mudflows) are a type of rapid landslide where soil, rocks and water flow together at high speed downslope. These natural hazards travel for long distances and pose risks to lives and infrastructure that they encounter in their flow paths. During a debris flow event, solid particle sizes and fluid segregate so that large particle are concentrated in the front, leading to high impact forces. This renders their behaviour both dangerous and physically complex so that there are several mathematical and numerical granular flow theories competing to explain their motion.This research seeks to improve our understanding of debris flows and the impact stresses they can cause to obstacles they encounter, by conducting a series of novel laboratory scale tests in 2D and in 3D on flows confined within model debris flow channels. In the 2D model experiments, the soil and rock will be replaced by acrylic particles, and a photoelastic method used to enable the forces in the individual particles to be determined as the material flows downslope without considering fluid interactions. The results then will be compared against current theories of granular flow in 2D in order to determine which theories best match the results in terms of particle motion and stresses induced in the particles. In the 3D experiments, the soil and rock will be replaced by glass particles and the water by an optically matched fluid which will render the mixture virtually transparent. A laser plane passing through the system then will create a visual slice of the flow at its centre, so that the 2D slice of particles will appear as dark against a bright fluid background during high speed motion. Capturing this behaviour via high speed photography will enable comparison with granular flow theories in 3D in terms of particle motion in the presence of fluid and away from sidewall boundary effects.In the second series of tests in 3D, an obstacle, representing a structural barrier to the flow or infrastructure, will be placed in the path of a model glass-and-fluid debris flow so that its interaction with the obstacle can be examined. As well as using more conventional techniques, the use of a novel method, holographic interferometry will be trialed to determine how the deformation and stresses in the structure itself are related to particle impacts from the model debris flow. This method can enable the detection of very small deformations over a whole object so is ideally suited to examining the complex interactions of multiple particle impacts with obstacles of differing shape and size.The overall outcomes will be a several datasets that can be used to better model debris flows numerically, which uniquely includes both the influence of a debris flow on a structure and a structure on a debris flow. It is hoped that the results may lead to better design of barriers to debris flows, enhancing and protecting the natural and built environment and hence leading to greater protection of human life.