Micro-mechanical modelling of unsaturated particle packings

Unsaturated soils consist of three phases: the solid phase (soil grains), the water phase (pore water) and the air phase (pore air). The content of pore water in the soil structure is defined by the degree of saturation. Depending on the degree of saturation different gas-solid-liquid interfaces are formed such as bubbles, liquid bridges or capillary interfaces. That in mind, it becomes obvious that stability, transport phenomena and forces within unsaturated soils highly depend on the degree of saturation. Further, the degree of saturation is a local property at soil grain scale rather than a global property. Within a soil, regions of high saturation can be spatially close to regions of low saturation. In order to describe, model and understand the behaviour of unsaturated soils, it is therefore necessary to understand the physical phenomena at soil grain scale. The proposed research project is concerned with the investigation of micro-hydraulic and micro- mechanical processes in partially saturated granular porous media by means of new modelling approaches and imaging experiments. In these experiments the imaging technique of computed tomography (CT) is used. These experimental techniques deliver detailed information of the behaviour of gas-liquid-solid granular systems. Based on that information numerical models based on Computational Fluid Dynamics (CFD) and Discrete Element Method (DEM) will be developed and further refined. The goal is to develop numerical models that are able to predict the behaviour of saturated soils and produce even deeper understanding of the underlying phenomena. In contrast to the visual experimental techniques, the numerical models can provide lots of additional information that is not easily accessible by experiments. For instance forces acting on the gas, liquid and solid phase are calculated at a scale smaller than the granular particles. This is of fundamental importance for understanding and modelling effects such as stability of such soils or other geotechnical questions. Given the wide field of expertise needed for the planned tasks, researchers at DCS Computing GmbH, who will focus on the development of numerical models, have teamed up with the Institute of Geotechnical Engineering and Construction Management at the Hamburg University of Technology.

No additional funding sources recorded.