Buildings, bridges and offshore infrastructure might one day stand on pilings modeled on snakeskin, based on research at the University of California, Davis, Department of Civil and Environmental Engineering. With surfaces designed to move through soil more easily in one direction than the other, snakeskin pilings would be easier to drive into soil but difficult to pull out.

It’s part of an effort to solve engineering problems by looking at what nature has already accomplished, said Alejandro Martínez, assistant professor of civil and environmental engineering at UC Davis.

“We’re using bioinspired surfaces to create solutions for civil engineering,” Martínez said.

One common problem in civil engineering is how to stabilize structures such as buildings, retaining walls or wind turbines in weak soils. Engineers typically anchor structures in place by driving pilings or installing anchors deep into the soil. Friction between the soil and the piling or anchor dissipates the load from the structure into the soil. 

Martínez became interested in snakes about four years ago because their scales are arranged asymmetrically so that they have more friction in one direction than the other. Indeed, different snake species have different specializations: Some are excellent burrowers while others are expert tree climbers. He collaborated with the Museum of Vertebrate Zoology at UC Berkeley, which has an extensive collection of snake specimens. Working with Professor Brian Todd, a herpetologist at the UC Davis Department of Wildlife, Fish and Conservation Biology, Martínez selected a few species to look at in detail. In collaboration with Duncan Irschick at the University of Massachusetts, Amherst, and Simon Baeckens at the University of Antwerp, Belgium, the researchers developed technology to measure the surface features of snakeskin in three dimensions to facilitate the translation to civil engineering applications.

Testing scale models 

In collaboration with Hans Henning Stutz at Aarhus University, Denmark, Martínez’s laboratory developed scale models of pilings based on snakeskin and tested them in the lab. Martínez’s team, including graduate student Kyle O’Hara, has also evaluated the performance of snakeskin-inspired piles at the Center for Geotechnical Modeling at UC Davis. The center’s giant centrifuge (9 m in radius) allows civil engineers to build scale models of soils and structures in them, and see what happens to them under different depths and other soil conditions.

Tests so far show that the snakeskin pilings generate high friction, shedding more building load high in the soil. They require less force to drive them into soil compared to a conventional piling that takes an equivalent force to pull out. Pilings that are easier to drive would save on time, energy and construction costs, Martínez said. The researchers have not yet tested them under earthquake conditions.

The work was described in recent papers in the Journal of Geotechnical and Geoenvironmental Engineering, Acta Geotechnica and the Journal of the Deep Foundations Institute.

The snakeskin piling research is part of a wider effort to draw on examples from biology for civil engineering. Other examples include using bacteria to stabilize soils against earthquakes and looking at tree roots to determine new ways to anchor buildings. The research is part of the  Center for Bio-mediated and Bio-inspired Geotechnics, which is funded by the National Science Foundation under award #1449501 and headquartered at Arizona State University. UC Davis, the Georgia Institute of Technology and New Mexico State University are all partners in the center with ASU. The CGM operates with support from NSF's Natural Hazards Research Infrastructure program through award #2037883.