For engineers and developers, erosion can be a big problem. The U.S spends around $5 billion per year on programs that aim to reduce soil erosion. To combat this, researchers are continuously developing methods and materials to reduce the erosion and the impacts of it. Here are just two studies that are making a big difference in the fight against erosion.

The First Step Is Knowing Why

One of the steps to developing erosion-resistant materials, is understanding exactly how erosion happens in the first place. A study done at the University of Minnesota shows how water droplets can erode hard surfaces.

Past studies have analyzed what happens at the moment of impact through high-speed cameras. In the University of Minnesota study, the researchers used a process they developed call high-speed stress microscopy to measure the force stress and pressure as the drops hit the surface.

This high-speed stress microscopy gives researchers a more quantitative look at the erosion process. The study found that force of the drop hitting the hard surface quickly spreads out faster than the speed of sound. This essentially creates a small shock wave. This shock wave creates a sheer force that can erode the surface given enough time.

Using this information, engineers can now create new, erosion-resistant materials that can stand up to the outdoors. The researchers imagine that future materials will be designed to decrease the shear stress of a droplet’s impact.

Additionally, this new method of observing droplet impact could give other researchers a new tool on their belt. The authors of the study hope to next study different textures and materials to see how this changes the force from the droplet impact.

Bio-Cemented and Polymer-Modified Loess Slopes

The addition of microbially induced calcite precipitation works well to stop sand erosion. Researchers at universities in China wanted to extend this application to loess slopes.

Loess slopes are primarily aeolian silt, which is silt that has been deposited largely through wind erosion. They are highly susceptible to water erosion. When loess slopes get wet, they lose surface strength and experience changes to their shear strength and friction resistance. When loess slopes get wet, the chances of catastrophic landslides increase significantly

In addition to the Microbially induced calcite precipitation, the study looked at adding polyacrylamide to the soil to increase the erosion resistance even more.

The slopes with just microbially induced calcite precipitation added still saw a high amount of soil lost, as did the slopes with just polyacrylamide added. The slopes treated with both had very little soil loss. The study concluded that this was due to the “stable spatial structure of CaCo3 precipitate, and the stronger resistance of PAM to tension or shear force”.

Adding 1.5 g/L of PAM had the best impact on reducing erosion with the least erosion and highest surface strength.

“The high erosion resistance of MICP-PAM treated slopes could be attributed to the stable spatial structure of precipitation, and PAM addition conveyed stronger resistance to tension or shear force,” the study’s authors concluded.

The treatment also “ensured a stronger freeze-thaw weathering resistance”. The surface strength did decrease as the number of freeze-thaw cycles went up, but researchers observed very little lost soil after 12 freeze-thaw cycles.