Could rubber tyre foundations help protect buildings during earthquake?

Many homes in Lombok have been destroyed. Image: EPA/Adi Weda.

At the time of writing, 436 people have died following an earthquake in the Indonesian island of Lombok. A further 2,500 people have been hospitalised with serious injuries and over 270,000 people have been displaced.

Earthquakes are one of the deadliest natural disasters, accounting for just 7.5 per cent of such events between 1994 and 2013 but causing 37 per cent of deaths. And, as with all natural disasters, it isn’t the countries that suffer the most earthquakes that see the biggest losses. Instead, the number of people who die in an earthquake is related to how developed the country is.

In Lombok, as in Nepal in 2015, many deaths were caused by the widespread collapse of local rickety houses incapable of withstanding the numerous aftershocks. More generally, low quality buildings and inadequate town planning are the two main reasons why seismic events are more destructive in developing countries.

In response to this issue, my colleagues and I are working on a way to create cheap building foundations that are better at absorbing seismic energy and so can prevent structures from collapsing during an earthquake. And the key ingredient of these foundations is rubber from scrap tyres, which are otherwise very difficult to safely dispose of and are largely sent to landfill or burnt, releasing large amounts of carbon dioxide and toxic gases containing heavy metals.

Rubber-soil mixture

Previous attempts to protect buildings from earthquakes by altering their foundations have shown promising results. For example, a recently developed underground vibrating barrier can reduce between 40 per cent and 80 per cent of surface ground motion. But the vast majority of these sophisticated isolation methods are expensive and very hard to install under existing buildings.

Our alternative is to create foundations made from local soil mixed with some of the 15m tonnes of scrap tyre produced annually. This rubber-soil mixture can reduce the effect of seismic vibrations on the buildings on top of them. It could be easily retrofitted to existing buildings at low cost, making it particularly suitable for developing countries.


Several investigations have shown that introducing rubber particles into the soil can increase the amount of energy it dissipates. The earthquake causes the rubber to deform, absorbing the energy of the vibrations in a similar way to how the outside of a car crumples in a crash to protect the people inside it. The stiffness of the sand particles in the soil and the friction between them helps maintain the consistency of the mixture.

My colleagues and I have shown that introducing rubber-soil mixture can also change the natural frequency of the soil foundation and how it interacts with the structure above it. This could help avoid a well-known resonance phenomenon that occurs when the seismic force has a similar frequency to that of the natural vibration of the building. If the vibrations match they will accentuate each other, dramatically amplifying the shake of the earthquake and causing the structure to collapse, as happened in the famous case of the Tacoma Narrows bridge in 1940. Introducing a rubber-soil mixture can offset the vibrations so this doesn’t happen.

A promising future

The key to making this technology work is finding the optimum percentage of rubber to use. Our preliminary calculations echo other investigations, indicating that a layer of rubber-soil mixture between one and five metres thick beneath a building would reduce the maximum horizontal acceleration force of an earthquake by between 50 and 70 per cent. This is the most destructive element of an earthquake for residential buildings.

We are now studying how different shaped rubber-soil mixture foundations could make the system more efficient, and how it is affected by different types of earthquake. Part of the challenge with this research is testing the system. We build small-scale table models to try to understand how the system works and assess the accuracy of computer simulations. But testing it in the real world requires an actual earthquake, and it’s almost impossible to know exactly when and where one will strike.

The ConversationThere are ways of testing it through large scale experiments, which involve creating full-size model buildings and shaking them to simulate the force from recorded real earthquakes. But this needs funding from big institutions or companies. Then it is just a question of trying the solution on a real building by convincing the property owners that it’s worthwhile.

Juan Bernal-Sanchez, PhD Resarcher, Edinburgh Napier University.

This article was originally published on The Conversation. Read the original article.

 
 
 
 

Wild boar are moving back to Genoa, and not everyone is pleased

A wild boar, c1933. Image: Getty.

Crossing the Ponte Gerolamo Serra in the Italian city of Genoa, I spotted a small crowd clustered by the river wall. I approached, intrigued, and peered over the wall to discover the subject of their delight: a sounder of eight wild boars – the adults sheltering from the heat in the undergrowth, while the juveniles foraged among the foliage that grows in the river bed during the dry summer months.

In any other city, such a sight might have been surprising. But in Italy, and particularly in the region of Liguria, where Genoa is located, the population of wild boars has been increasing at such a rapid rate that these incidents are now common. Across the country, it’s estimated that the population has risen from 600,000 to 1m over the past decade.

But while wild boars may look comically out of place trotting about the city, it’s actually a natural result of the way people have migrated – and the wars they have fought – over the course of recent history.

Making a comeback

A species native to Europe, the wild boar (or “cinghiale”, in Italian) largely disappeared from its historical territories during the 18th and 19th centuries. Their decline was widely attributed to the combined effects of habitat change, competition for space and resources and, of course, hunting.

Wild boars were a prized quarry, revered for their ferocity – and the danger involved in pursuing them. According to local folklore from the region of Liguria, the last truly wild boar was hunted and killed in 1814, in the province of Savona.

After an absence of more than a century, wild boar began to return to Liguria, and to the neighbouring region of Piedmont. A further influx occurred during World War I, when it’s believed that military activities in the south-east of France forced parts of the population back into Italy over the Alps.

Although hunting fraternities were quick to augment this fledgling population with wild boars transported from elsewhere, the return of the species was primarily due to natural causes. From the 1950s onwards, traditional agricultural practices were abandoned as more and more people moved from rural towns into the cities. This meant that large areas of formerly cultivated terraces and pastures were rapidly overgrown, fast becoming dense secondary woodlands.

A city gone wild

This spontaneous “rewilding” has become a controversial issue in the region. Many conservationists and environmental organisations consider the region’s return to a “wild state” a success. But others believe that the encroaching wilderness signals a loss of traditional woodland knowledge and a reduction of biodiversity, associated with the pastures and meadows.


The province of Genoa is among the areas most densely populated by wild boar in Italy, with an estimated 25 boar per 10km². Rewilding processes have brought woodlands to the city limits, blurring the boundary between rural and urban areas. The species has expanded beyond the hinterlands, colonising highly urbanised, densely populated city spaces in Genoa, drawn by the abundance of food waste created by humans.

In 2009, the infamous boar Pierino made his home at Righi, on the outskirts of Genoa, where he was routinely fed with focaccia by enthusiasts. Today, a family of wild boar call the Albergo dei Poveri – a historical hostel for the Genoese poor in the city centre – their home.

But while their antics are often recorded and shared with glee on social media, the threats posed by the presence of wild animals has become a preoccupation for the city’s municipal administration.

Boorish behaviour

Wild boar have been involved in a number of traffic accidents, and have proven to be particularly dangerous when with their young, attacking dogs and even people. The city council in Genoa has put forward many proposals to reduce the number of animals in the city, ranging from forced removals, to sterilisation, increased attention to waste disposal and approved hunts. About 90 wild boar were reportedly culled in 2018.

Needless to say, each of these measures has been hotly debated. Animal advocacy groups staunchly oppose the proposals, and sometimes obstruct the authorities’ attempts to take action, often sending patrols to care for the animals, and even give them names. But other residents are displeased with the animals’ presence in the city, and have consulted with the council on how to address the problems that they cause.

And so Genoa continues to grapple with thorny issues surrounding the presence of wild boar in the city, with the city authorities seeking to resolve a polemical issue that embroils the lives of animals and humans alike. So far, a collective, coherent and communally agreeable strategy has proven evasive; one that considers the need for public safety, hygiene and health with the ethical responsibilities towards to wild boar themselves.

Meanwhile, the animals themselves continue to lounge and forage beneath the Ponte Gerolamo Serra and elsewhere, bringing a little of the wilderness into the city.

The Conversation

Robert Hearn, Assistant Professor in Human Geography, University of Nottingham.

This article is republished from The Conversation under a Creative Commons license. Read the original article.