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Monday, December 5, 2022

UC Davis researchers combine civil engineering and biology to model stronger infrastructure using snakeskin

Snakeskin has frictional properties that can be applied to surfaces of large column structures to securely support large buildings

 

By YASH RATHI — science@theaggie.org 

 

At the UC Davis Center for Geotechnical Modeling, researchers used the facility’s large geotechnical centrifuge to test a design inspired by the unique properties of snakeskin. According to their website, “A geotechnical centrifuge is used to conduct model tests to study geotechnical problems such as the strength, stiffness and capacity of foundations for bridges and buildings, settlement of embankments, stability of slopes, earth retaining structures, tunnel stability and seawalls.”

Alejandro Martínez, Ph.D., who is the lead author on the research study and an associate professor of civil and environmental engineering at UC Davis, explained the team’s interest in snakeskin and its potential real-world applications to infrastructure. 

“Snakeskins are a promising bioinspiration,” Martínez said. “Their belly scales have evolved in such a way that it reduces friction as it moves ahead and increases friction if moved in the opposite direction. Their ventral [belly] skin helps them to move more efficiently through soil and slide up a tree without sliding down.” 

This natural phenomenon is called frictional anisotropy, and it allows snakes’ to experience a change in surface friction depending on the surfaces they interact with.  

Martínez believes that the snakeskin surface can help improve the strength and efficiency of geotechnical structures like driven piles, which are rigid columns that form the foundations of large buildings, and the anchors of offshore structures and tunnels, because these structures require different levels of friction. For example, low friction is required for installing driven piles while high friction is required for anchoring a pile. 

Until now, it has been hard for researchers and engineers to create structures that are both easy to install and difficult to remove — as they need to serve as strong anchors — especially on dense soil.

“Installing driven piles is a challenge in the field, especially on denser soils,” Martínez said. “Imagine a pile that’s easy to install and yet strong enough to support the applied loads. We think snakeskin’s frictional properties will reduce the difficulty of establishing driven piles in more difficult terrain.”

Martínez explained that using a bioengineered snakeskin structure would allow piles to be installed more firmly and anchor the foundation more securely to the ground. 

Additionally, Martínez said that determining the snake species that has the best skin to use for the geotechnical structures was difficult. To do so, he and his team collaborated with Brian Todd, Ph.D., who is a coauthor on the study and a professor in the UC Davis Department of Wildlife, Fish and Conservation Biology. Todd suggested certain species to examine, and the team eventually selected the western hognose snake, parrot snake and Saharan horned viper as potential candidates. 

 “One of the important parts of our bioinspired geotechnical work is learning about biology,” Todd said. “As a biologist, I helped Martínez’s team better understand the relationship between the topography and snakeskin of interest so they could tackle and maintain the friction in the process of locomotion in these large structures.”

Using the three snake species above, the team developed a geometric design for each of their ventral skins in the lab to test and understand how they behaved on different surfaces. 

“With the snakeskin scans, we realized that many of them had an asymmetrical sawtooth pattern,” Martínez said. “With the three-dimensional printed surfaces, we then applied the snakeskin patterns onto structure surfaces, which would make them stronger than the typical material surfaces used, like concrete or steel. From this, we learned that we could make directionally-dependent, stronger surfaces.”

They created model driven piles with snakeskin-inspired materials and conducted various tests on them using the large geotechnical centrifuge at the UC Davis Center for Geotechnical Modeling. These tests helped Martínez’s team understand the behavior of the pile when put in the soil and how its application reduced or increased friction. 

The study concluded that the snakeskin surface produced a lower friction when the pile was being installed but a higher friction during pullout. This means that the use of bioengineered snakeskin could allow for easier installation of piles and make them more resistant to being uprooted once they are in the ground. Martínez believes that this invention, and similar research into other bioinspired, geotechnical tools is promising for increasing the efficiency and strength of these structures in future construction.

 

Written by: Yash Rathi — science@theaggie.org