Predicting landslides in an uncomplicated and non-destructive manner is the goal of geomechanic Bettina Albers. To develop an acoustic testing method, she is using the continuum model of the propagation of sound waves in soils and adding the previously unconsidered factor of wave propagation. The model, which the private lecturer at TU Berlin derives mathematically, is also relevant to questions of oil production and the remediation of contaminated soils.
»I sound out the depths«
You use sound waves to study the ground?
Conventional methods rely on borings to obtain soil samples. But those techniques destroy the soil. In the theoretical part of my work, I develop a foundation for non-destructive test methods, which are also less expensive. My approach relies on the properties of acoustic waves. When you send a signal through the ground and measure the wave velocity, for example, it lets you draw conclusions about the soil composition and firmness. That is also the route special- ists took to stabilize the Leaning Tower of Pisa, by the way. Other wave properties may even be useful in predicting earth- quakes: once the soil reaches a certain saturation level, one of the sound waves virtually doubles in speed. If this saturation is achieved after heavy, prolonged rains, for example, this increase in speed can be detected to activate a warning system.
So your research is theoretical with specific practical benefits?
My work is situated in the category of basic research, but as an engineer, I am also always interested in practical applications. One of my concerns is how to combine engineering approaches with mathematics and utilize the complex modelling possibilities for practical applications. I find it fascinating to transfer the processes that occur in the depths of a medium to an abstract mathematical level. It is especially interesting with porous media, because you need to account for the interplay of solids and interstitial fluids. These small cavities contain immiscible fluids flowing through them; be- cause the fluids cannot combine, a surface tension emerges. Even when the saturation remains the same, what we call “capillary pressure” varies, depending on whether water is entering or exiting the soil. In my project as an Einstein Junior Fellow, I develop a mathematical model that describes the impact of these factors on the propagation of sound waves in order to create even better non-destructive test methods.
What do you think about when you are studying sound waves?
Wave propagation is a bit like life, actually. When a wave is dampened and its amplitude slowly decreases, we might compare it to our energy as we approach the end of our journey on this earth. The amplitude of a wave with ups and downs also shows us parallels: setbacks often lead to positive events. For me, one of those positive events has been the opportunity to have so much freedom in my field thanks to support from the Einstein Foundation.
Interview: Mirco Lomoth