New geotechnical approaches to soil biological processes

We are investigating soil displacement processes such as by earthworm burrowing and plant root growth. These processes occur on the surface of most of our planet and change the soil’s properties. For example, they aid water and air movement through the soil and so help plant growth. Plants, grown in the soil support most life on earth. Understanding such processes is important for food and fibre production, particularly as climate change may alter soil properties.
The project unites a team of biologists, soil scientists and engineers. Some of the team study interactions between the soil, plant growth and soil organisms. The civil engineers quantify soil as a material to support buildings and other structures (so they don’t settle into the ground or collapse) and as a material to be removed when tunnelling. They experiment and model how foundations and tunnels work for safe and efficient construction. By combining experiments and bringing our knowledge together we will improve understanding and management of the relevant biological systems and processes. Finally, the biology may also lead to the improvement of engineering methods by mimicking natural processes.

Burrowing processes are fundamental to life in both terrestrial and marine-sedimentary ecosystems. In combination, these habitats are the surface of most of our planet. Terrestrial life depends on maintaining soil structure adequate for plant growth. This structure depends largely on the burrowing activity of soil organisms and plant roots in deforming the soil to generate complex networks of interconnected pore space that control solution retention and transport, gas diffusion and mass-flow.

To-date burrowing processes have been studied mainly by biologists with little background in engineering disciplines. A step-change in understanding these processes will be made possible by exploiting the latest developments in geotechnical engineering: In this proposal a postdoctoral geotechnical engineer will hop disciplines to bring a fresh perspective to the study of biological burrowing and soil penetration processes. The postdoc will be based at the plant and soil science research labs at the SCRI - facilities shared with the Division of Plant Science of Dundee University (5* RAE rated, School of Life Sciences). This work will open a new area for research at the soil engineering-biology interface. We anticipate the knowledge and skills generated will be applicable in widely ranging disciplines.

Both roots and earthworms penetrate soil by deforming the surrounding matrix and, in the case of earthworms, ingesting soil. We will study the penetration of soil by both plant roots and earthworms, applying Particle Image Velocimetry and other imaging approaches to measure soil deformation around biological organisms in physical model tests, and numerical modelling of soil mechanical behaviour. The biological mechanisms of soil penetration identified from these investigations will be compared with geotechnical installation processes (e.g. pile-installation, pipe jacking, and tunnelling). We will evaluate whether current geotechnical analysis methods are applicable to the biological systems studied. Biomimetic approaches (i.e. using biology to inform and improve engineering design) will also be explored.