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.

 
 
 
 

Five ways in which the rest of the world can avoid the homelessness crisis plaguing the US

Housing for all. Image: Nicobobinus/Flickr/creative commons.

Homelessness is a growing problem in the UK, where the number of people sleeping rough has doubled since 2010, yet it is dwarfed by the scale of the issue in the US. More than 500,000 homeless were found across the US during just one night, compared to the UK’s 2017 count of 4,751. Changes in the definition of homelessness and flawed methodologies suggest that the true number for the US could be anywhere from 2.5 to 10.2 times greater.

Millions more live in overcrowded or slum housing, forced to choose between the damage that poor conditions do to their physical and mental health, and the street. All of the US’s housing issues – from foreclosures to evictions to poor conditions – hit communities of colour the hardest.

This is due to a legacy of discrimination, which continues to undercut any commitment to safe and decent housing for all residents, whether in the private or public sector. In my recent book, City of Segregation, I explain how the long, violent history of creating spaces for the white and privileged classes is embedded in a number of practices, which continue in US cities to this day.

Exporting inequality

As private developers and investors seek out urban land in major cities around the world to secure their fortunes, real estate patterns and practices developed within the US are increasingly being observed elsewhere.

In cities as diverse as London, Sydney and Durban, community groups which have been working for decades to improve their neighbourhoods languish with little public or private resource. Meanwhile, developers create spaces for foreign investors and new residents, who anticipate certain protections and privileges such as greater security, high quality amenities and neighbours with similar interests and backgrounds.

This is a driving force behind rising evictions and the criminalisation of homelessness, alongside gated communities, hostile architecture, “broken windows” policing with its focus on prosecuting activities such as graffiti or jaywalking and the growing privatisation of public spaces through regeneration.

But there is still time for other countries to choose a different path. The UK, in particular, can build on the legacies of the post-war political consensus that all residents should have access to quality housing, and its acknowledgement of institutional racism and some history of government anti-racist campaigning.

Both legacies should be improved, but a renewed commitment to a programme of housing and anti-racism are central to increasing equality, prosperity and well-being for all. Based on my research, I’ve come up with five steps which the UK and countries like it can follow, to ensure that future development reduces – rather than drives – homelessness and inequality.


1. Build social housing

Unlike the US, the UK acknowledges a right to a home, and within living memory provided it for a huge swathe of British society. Social housing – whether in the form of traditional council flats, cooperatives or community land trusts – provides a variety of housing types and keeps rents from rising too far beyond wages.

When social housing is widely available, it makes a huge difference to people who – for one reason or another, and often through no fault of their own – become homeless. With social housing to fall back on, homelessness is a temporary condition which can be safely resolved. Without it, homelessness can become a life-destroying downwards spiral.

2. Preserve and expand community assets

Severe segregation in the US stripped entire communities of access to quality food, jobs, education, green spaces, services, banks and loans. Poverty is endemic, and can easily tip into homelessness. While far from perfect, the UK’s post-war commitment to universal provision of services, such as education and health care, and building social housing across all neighbourhoods underpinned a surge in upward mobility.

This achievement should be salvaged from the damage done by Right To Buy – a policy which sold off social housing without replacing it – and austerity, which has prompted a sell-off of public assets and land, as well as the closure of childrens’ services, libraries and community centres.

3. Decommodify housing

A market geared towards building apartment blocks for the portfolios of investors who will never live in them cannot produce the kind of housing and neighbourhoods which residents need, much less at a price they can afford.

While London has been badly affected for some time, this trend is now spreading to other areas of the UK and Europe. Local and national governments must act to prevent global demand for housing as investments from driving prices beyond the reach of those who need real homes.

4. Build communities, not walls

Gates, bars, armed security and homeowner restrictions are all ugly traits of private housing developed within the US context of desperate inequality and racism. The UK has a long and vibrant tradition of community development, creating a supportive built environment and social infrastructure of schools, libraries and other municipal services for residents.

Community assets. Image: Helen K/Flickr/creative commons.

This kind of development, and the social mobility and growing equality it fosters, safeguards public health and safety – not big walls, barbed wire and security guards. The private rented sector in the UK should be regulated to bring it more in line with Europe, where tenants prosper with security of tenure and strong regulation of rents and rent increases.

5. Raise your voice

Those who are bearing the brunt of our current housing crisis must be at the centre of efforts to change it. From tenants’ associations and renters’ unions, to campaign groups such as Justice for Grenfell, it’s vital to support those voices advocating fairer housing rights.

This also means rejecting austerity’s constant cuts to public services, funding social support for physical and mental health and ensuring that homes are safe, decent and secure, to create a safety net for those who are working to improve their communities.

The Conversation

Andrea Gibbons, Researcher in Sustainable Housing and Urban Studies, University of Salford.

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