Identification of poly-disperse granular fabric for the assessment of the stability of widely graded soils under hydraulic load

颗粒在土壤中的运移总是会引起力学性质的变化。这将影响土壤的抗应力能力和土方工程的可靠性。为了评价土壤的稳定性，分析土壤的结构及其过渡是很重要的。虽然在岩土工程中对土壤物质的运移过程进行实验和分析研究有着悠久的传统，但没有基于主要结构分析的稳定性标准。本研究项目的目的是确定广泛分级的土壤的结构在其承受土壤物质运输的能力方面。在确定土壤结构的基础上，导出了颗粒流动性和土壤稳定性的一般评价。通过实证调查、3D计算机断层扫描图像和数值模拟，对土壤的结构进行可视化、分析和识别。在这些分析中，土壤是由球形颗粒堆积而成的。这种颗粒填料将进行实验研究和数值模拟。为了将这两种方法联系起来，建立了实验生产的填料的三维数据库。数字图像处理方法确定了填料的相关特征值。所得到的填料用于验证和验证数值模拟。主要目的是识别织物和评估粒子的迁移概率。根据评估结果，填料暴露在特定的水力载荷下。该结果允许对广泛分级粒径的填料的可移动颗粒的稳定性和整体迁移率进行评估。本研究发展了识别颗粒填料结构和颗粒输运的方法。在此基础上，根据织物的粒度分布和容重，可以确定织物的特征矩阵类型，并预测其迁移率。因此，这项研究将有助于评估土方工程在水力荷载下承受土壤物质运输的能力。这样可以进行更准确的评估，最大限度地减少防洪土方工程的不确定性。

The transport of particles in soil will always cause a change in the mechanical properties. This will affect the soil's capacity to withstand stresses and the reliability of earthworks. In order to assess the soil's stability, analysing the soil's fabric and its transition is important. Although there is a long tradition in geotechnics of experimental and analytic investigations into the process of the transport of the soil's material, there are no criteria for its stability based on analysis of the dominant fabric.The aim of this research project is the identification of the fabric of widely graded soils in respect of their capacity to withstand transport of soil material. On the basis of an identification of the soil's fabric, a general assessment of particle mobility and the soil's stability is derived. The soil's fabric is visualised, analysed, and identified through empirical investigation, 3D computed tomography images, and through numerical simulations. In these analyses, the soil is represented by granular packing of spheres. This granular packing will be experimentally investigated and numerically simulated. To link both methods, a 3d data base of the experimentally produced packing is built. Digital image processing methods determine the relevant characteristic values of the packing. The resulting packings are used to validate and verify the numerical simulation. The main objective is the identification of the fabric and the assessment of the probability of mobility of particles. Based on the results of this assessment the packings are exposed to a specific hydraulic load. The outcome allows an assessment of the stability and global mobility of the mobile particles of packings of widely graded particle sizes.This research develops methods of identification of the fabric of granular packings and particle transport. Based on this in dependency of the particle size distribution and bulk density a characteristic type of matrix for the fabric can be identified and the probability of mobility can be predicted. As a result, this research will contribute to techniques for assessing the capacity of earthworks to withstand transport of soil material under hydraulic loads. This allows more accurate assessments that minimize uncertainties in earthworks of flood protection.