Preferential flow dynamics in unsaturated fractured porous media: Relationship between fracture network topology and dual-domain model parameterization

该建议的主要目的是建立一个明确的一组功能之间的关系几何/拓扑结构的裂缝网络和参数化的双域模型的背景下，非饱和裂缝流动动力学。为了了解非饱和裂隙网络中优先流动路径的发生和动力学，将进行实验室和现场实验。重点在于识别易于测量的几何和拓扑参数的网络（交叉类型，孔径，裂缝密度，方向，矩阵属性），并在这些参数和“吝啬”双域模型，它可以被应用到模拟散装系统响应输入信号之间的函数关系。具体来说，我们要建立一个非饱和裂缝网络的属性和活动面积分数f（深度，时间）之间的函数关系，以及裂缝界面面积密度M在各种口味的双域models.Laboratory实验将进行研究的启动和形成的优先流路径在良好的控制条件下的裂缝网络。将构造具有不同孔径宽度的非饱和（准二维）裂缝网络，以产生由毛细力（< 0.7 mm）或惯性力（> 0.7 mm）主导的非饱和裂缝流，并通过使用地质材料来解释与多孔基质的扩散交换。流态的源响应形成影响裂缝网络内的流路的质量分配和引导。此外，裂缝的几何形状和拓扑结构的连接系统地改变，以确定优先流形成的影响。裂缝连接的拓扑结构作为连通性的度量，并且可以在实验室和现场实验中容易地确定。现场实验安装在属于三叠纪Muschelkalk的地质构造的露头中，具有明确的裂缝特征（即，孔径宽度、方向和频率），而尺寸与实验室布置的规模相匹配。现场研究主要作为一个验证的结果，从控制良好的模拟实验，并了解到什么程度的平面二维露头功能可以用来预测三维系统中的流动动力学。分析工作是为了表达裂缝网络的几何和地形方面的建立和效率的优先流动路径之间的连接。因此，我们希望测试我们的假设，并最终再现通过裂缝网络的流量。

The main objective of this proposal is to establish a definite set of functional relationships between geometry/topology of fracture networks and the parameterization of dual-domain models in the context of unsaturated fracture flow dynamics. In order to understand the onset and dynamics of preferential flow paths in unsaturated fracture networks, both laboratory and field experiments will be carried out. The focus lies on the identification of easy to measure geometrical and topological parameters of the networks (intersection type, aperture, fracture density, orientation, matrix properties), and on the functional relationships between those parameters and "parsimonious" dual-domain models, which can be applied to model the bulk systems response to input signals. Specifically, we want to establish a functional relationship between the properties of unsaturated fracture networks and the active area fraction f(depth, time), as well as the fracture interfacial area density M employed in various flavours of dual-domain models.Laboratory experiments will be carried out to study the onset and formation of preferential flow paths within the fracture networks under well controlled conditions. Analogue (quasi-2D) fracture networks with various aperture widths will be constructed to generate unsaturated fracture flow either dominated by capillary (< 0.7 mm) or inertial forces (> 0.7 mm) and account for the diffusive exchange with a porous matrix by using geological materials. The source-responsive formation of flow regimes affects mass partitioning and channelling of flow paths within the fracture network. Furthermore, fracture geometry and topology of the connections are systematically altered to determine the impact on preferential flow formation. The topology of fracture connections acts as a measure for the connectivity and can be easily determined, both in laboratory and field experiments. The field experiment is installed in an outcrop of geological formations belonging to the Triassic Muschelkalk with well-defined fracture features (i.e., aperture width, orientation and frequency) while the size matches the scale of laboratory arrangement. The field study primarily serves as a validation for findings from the well-controlled analogue experiments and to understand to what degree planar 2D outcrop features can be used to predict flow dynamics in three-dimensional systems. Analytical work is done to express the connection between geometrical and topographical aspects of the fracture network to the built-up and efficiency of preferential flow paths. Hereby, we hope to test our hypotheses and ultimately reproduce flow through the fracture network.