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.

 
 
 
 

In New Zealand, climate change is driving an eco-nationalist revival

The green and pleasant land of the South Island. Image: Getty.

“Ten years ago I would have called them settler f*****g land squatters,” Mike Smith, Maori-dom’s most tenacious activist, said last November as he reflected on the agriculture industry’s central role in driving climate change. “Now I have to try and get these people on board.”

Smith is infamous for taking a chainsaw to Auckland’s most prominent tree on a damp October night in 1994 in protest of the “Pākehā” – or white European –dominated government’s fiscal envelope restraining treaty settlements. Now he’s turned his hand to another cause close-to-home for the Maori, New Zealand’s indigenous population: the environment.

“We’re super vulnerable, like we are to anything,” Smith says. “When it comes to climate change it’s like the poorest people in the world are going to be hit the hardest first, and that’s a lot of us.”

Prime Minister Jacinda Ardern appears, at least rhetorically, the most sympathetic leader to his cause in a decade. In her campaign launch speech late last year, she made the future government’s position clear: “Climate change is my generation’s nuclear free moment.”

This message should resonate with followers of her Labour party: the NZ left has long nurtured an environment-orientated “culture-of-protest”. So Ardern’s call to arms was bound to gain her loyal support among children of the 1960s and ‘70s, who led the march against nuclear ship visits, spurring on the government of the time to wriggle out from the US nuclear umbrella, and place a ban on foreign nuclear ship visits.

Now, it is to the tycoons of deep sea oil exploration they aim to close NZ’s ports.

In this, Smith is not short of support locally, with marches run by grassroots organisations and international animal welfare funds beginning to gain traction with every day New Zealanders. In this, Ardern’s prediction is correct: the Coal Action Network Aotearoa (CANA), is reminiscent of the Campaign for Nuclear Disarmament (CND), an earlier cluster of left-wing pacifists and nature lovers who drove the creation of the nuclear free zone.  

In December, 15,000 passionate protesters marched through the capital. And with the government’s recent ban of offshore oil exploration projects, Jeanette Fitzsimons, former Green party co-leader and the head of CANA, is optimistic about similar change to the energy and farming sectors.

The Labour-NZ First-Green party coalition seems focused on setting a new global precedent, weaning NZ away from a United States which has jettisoned the Paris Agreement. The move replicates another 20 years ago, when New Zealand’s anti-nuclear movement was central to an upsurge in New Zealand nationalism. Now, the same sense of going it alone on foreign policy is apparent both locally and in Parliament.

Dr. Gradon Diprose, a senior lecturer at Massey University, argues that this echoes an older expression of colonial nationalism, that saw “New Zealand as a land of natural abundance”. This: “eco-nationalism” is centered on “protecting certain visions of picturesque landscapes and unspoiled natural beauty”. The slogan “Clean, green New Zealand” is prevalent in popular culture and tourism marketing. The public seems to have latched onto it too, and ranked keeping NZ’s waterways “clean and green” top of a recent survey of of kiwis’ top concerns.

Three decades ago, it was the 10 July 1985 sinking of the Greenpeace flagship Rainbow Warrior that thrust local activists’ fears into the public eye, resulting in an almost nation-wide expression of climate-protectionism.


The bombing, a French intelligence operation sparked by Greenpeace’s calls for an end to foreign nuclear testing in the Pacific, galvanised a great deal of change to New Zealand’s overseas defence policies. A lack of censure from New Zealand’s Western allies drove Wellington to distance itself from the United States, while the shock of seeing a friendly nation violate NZ’s sovereignty left many at home seething.

Thirty years on, the foreign policy split throughout the Anglosphere, regarding Russian-Western relations, globalism, and the old international rules-based order, is becoming wider. Climate change is just the tip of the iceberg.

Most Kiwis you talk to will shake their heads in disapproval at US president Donald Trump’s scandalous outing last year in Helsinki. But US defiance of internationally brokered climate resolutions is something they can see clearly reflected in rural communities across the country.

The country saw records broken at both ends of the extreme weather spectrum last year. As 2018 kicked off, Kiwis sweltered through the hottest summer on record, while in Golden Bay, a small inlet near the northern tip of the South Island, residents endured the largest flood in 150 years. So, when President Trump tweets “So much for Global Warming”, the majority of New Zealanders look back fondly on NZ’s 1985 decision to boycott the “ANZUS” treaty, putting New Zealand at odds with its war-time ally America on defence legislation.

Public calls to take the same track on environmental regulation have become louder in the wake of Donald Trump’s election. The former US Secretary of State, Rex Tillerson, received a frosty “unwelcome” while on a flyby to the capital in 2017, with the New York Times’ Washington correspondent, Gardiner Harris remarking: “I’ve never seen so many people flip the bird at an American motorcade as I saw today”. Protests against President Trump’s stance on climate change are beginning to gain greater traction further still, with the hundred-strong “march for science” setting the tone for the new government later that year.

New Zealand certainly isn’t afraid of radicalism, and its activists are persistent. It’s already banned single use plastics in supermarkets. Plenty more is to come, Smith says.

And yes, reform is going to inhibit sometimes vital industries: “It doesn’t matter which way you spin the dice on this, whatever’s being done is going to hurt. People who are looking for a painless way of mitigating climate change, [but] I don’t think there is one.”

But among Smith’s troupe of climate agitators, the feeling is that, without drastic change, “the land”, the heart of the Maori ethos, is going to be hurt far more.

Back in Auckland, NZ’s financial hub, an electric scooter craze is gripping the city. This, too, has gained the support of local environmentalists. In New Zealand, a national sense of pride is always coupled with a certain eccentricity. In a country this size, change always starts small.