Tree-roots inspire anchor design

Dr Pierre Rognon from the School of Civil Engineering’s particles and grains laboratory, and whose research aims to predict conditions under which soil moves, including landslides or avalanches says:

“Our recently published work shows root-like anchor structures could add strength to items such as transmission towers, utility poles, submerged pipelines, tunnels and offshore oil rigs- structures that are dependent on effective soil anchoring strategies.”

His research group used granular model tests to assess the pull-out capacity of root-like anchors.

“The quality of anchoring is characterised by the pull-out capacity, F0, which is the maximum tensile force an anchor can sustain before moving upward,” says Dr Rognon.

“We developed several models to predict the pull-out capacity of shallow anchors in granular soils.”

Results revealed the amount of materials required for an anchor modelled on trees (or fractal shaped) were much lower than that of traditionally shaped anchors making them more cost effective.

Rognon’s team will now conduct a series of experimental pull-out tests of differing fractal geometries buried at different shallow depths in model granular soil.

“The pull-out capacity is governed by the weight of the soil that would be mobilised when the anchor moves upward, “ says Dr Rognon.

Inspiration for the research stems back to Dr Rognon’s childhood in France.

“I have always loved being in nature and appreciated how fascinating and smart it can be,” says Dr Rognon.

“Since I can remember, I’ve always climbed trees, first when I was a kid to get the best cherries that are high up, and now sometimes to trim them.

“When I was a kid, I was amazed by the difficulty of uprooting their stumps - quite a pain when my role was to clear the garden.  Even for the smallest trees, it is really hard get them out of the ground without proper equipment.”

Translating this annoyance into new and improved geotechnical designs came more recently, four years ago, he remembers exactly when:

“I was walking back home from my lab in Marseille on a long leafy street the buses I normally took were on strike. I remember my childhood fascination with trees and their ability to stay anchored.”

Shivakumar Athani, a PhD geotechnical researcher in the School of Civil Engineering, who recently joined Dr Rognon’s team from India says nature’s root system has also fascinated him.

“I developed a love for the garden from my grandmother who was a school teacher in Hattaragi, India and I visited her in the holidays. What fascinated me was, though the roots of small plants are not deep, sometimes it was very hard to pull them out and we needed the help of some tools to uproot it completely,” says Shivakumar.

“Nature has so many things which we can explore. Now I am realising that soil is not a concrete” and “Roots are not homogeneous like steel, sometimes soil can hold the trees very firmly and can offer enormous resistance for uplift.” 

Shivakumar will bring his expertise to the team which includes a Bachelor of Civil Engineering from the Basaveshvara Engineering College, Bagalkot, Karanataka in India and a Master of Technology (Soil Mechanics and Foundation Engineering) from the S V National Institute of Technology, Surat, Gujarat.

Dr Rognon’s team is working with industry partner Anchoring Rope and Rigging Pty Ltd to develop innovative anchors for geotechnical applications.

Mr Rob Stockl, AR+R Manager said: 

"Research in this area of construction is vital to providing innovative solutions and we are delighted to have commenced working with the University of Sydney civil engineers."