Tree root shaped anchors

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In an engineering breakthrough, researchers discover tree root-like structures are stronger than traditional anchors

Nature’s skyscrapers have long intrigued geotechnique expert Dr Pierre Rognon, particularly the innate capacity of trees to stay anchored through varying weather patterns and in diverse soil systems.

Taking inspiration from the efficacy of its complex root system, Dr Rognon is leading a world-first Sydney University study on the pull out capacity of tree root-like anchors for applications in the field of civil engineering.

With an interest in soil stability, structural dynamics and earthquake engineering, Indian researcher Shivakumar Athani, who shares Dr Rognon’s fascination for tree roots, has recently joined the study.

Tree root anchor.indian link

Preliminary investigations at the School of Civil Engineering’s particles and grains laboratory reveal root-like structures could provide greater stability while also being more cost effective to produce.

The researchers have found that anchors modelled on the fractal-shaped roots of trees required much less material to build, making them more cost-effective compared to traditional shaped anchors.

Their findings will have far reaching implications for the construction industry. Transmission towers, offshore oil rigs, utility poles, submerged pipelines as well as tunnels, which are highly dependent on effective soil anchoring strategies could be made more stable with fractal-shaped root structures.

tree root anchor.indian link

“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,” said Dr Rognon, whose research aims to predict conditions under which soil moves, including landslides or avalanches.

“We are the first to produce the tree root design and hope to use our knowledge to convert the concept into engineering solutions. We have already worked out several models to predict the pull-out capacity of shallow anchors in granular soils. The next step is to assess the effectiveness of different fractal geometries when used in various shallow depths in the soil,” he told Indian Link.

“Pull-out capacity is governed by the weight of the soil that would be mobilised when the anchor moves upward. This is why even small trees planted in shallow soil can be very difficult to uproot without the proper equipment,” Dr Rognon explained.

Like Rognon, Athani developed a love for gardening as a schoolboy. His grandmother, a schoolteacher in Hattaragi, was a tower of inspiration.

“Nature has so many things which we can explore,” said Athani, who has a Bachelor of Civil Engineering from the Basaveshvara Engineering College, Bagalkot and a Master of Technology (Soil Mechanics and Foundation Engineering) from the SV National Institute of Technology Surat.

“Trees are a great example of adapting to adverse conditions like wind loading. If you examine tree roots carefully, you will observe that those on a windward side develop deeply and profusely, offering natural resistance. Likewise, in sloping terrain, roots are stronger where soil is naturally weak. 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,” he added.

According to the PhD student, part of the breakthrough in biomimicry comes with realising that soil is not concrete.

“Roots are not homogeneous like steel. Sometimes soil can hold the trees very firmly and can offer enormous resistance for uplift,” Athani said.

Incorporating branching and tortuosity, the study is closely looking at ways to improve anchor capacities by integrating novel strategies with numerical modelling.

“We also want to further explore design options and understand why some design shapes work better to optimise our results,” Dr Rognon clarified. Three-dimensional printing, currently unsustainable because of operational costs, is also in his sights.

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

“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,” a spokesperson for the company said.