Friday, July 1, 2011

The Sound Foundations of Engineered Earth Construction

Earth construction has recently attracted great interest as post-Peak building method for the First World. (By post-Peak methods, I mean methods of producing useful products which are suitable for a declining or collapsing economy whose resource base is drying up.) The reasons for this interest have to do with looming resource constraints, in particular, the resources required for construction methods which have become standard over the last hundred years in the developed world. However, the principles of proper earth building design and construction must be thoroughly understood and properly implemented in order to avoid loss of life due to failure and collapse of buildings. There is a strong need for validation of techniques, practices and principles of structurally sound earth building. This validation must be accomplished via experimentation and mathematical modeling and analysis.

This validation is also of special interest in the Third World (also known as the developing world), where, according to at least one source, approximately one fifth of the world's population lives in adobe and rammed earth structures, and where, according to another source, more than 90 percent of the population in moderate to severe seismic zones is living and working in non-engineered earth buildings. A body of work now exists which documents the behavior of earth buildings when subjected to various loading events, including seismic and wind events. This development of this body of work has been spearheaded by engineering professionals, universities and governmental agencies both in the developing world and in the First World nations of the Global South.

This work reveals some surprising facts, both with regard to safe earth construction best practices and with regard to the flow of useful information in the developing world. As far as the flow of useful information, two things can be observed. First, there is a much greater proportion of public-minded engineering and technical professionals in the developing world compared to professionals in the First World. This is seen in the willingness of researchers to openly and freely disseminate their published work via the Web without charging rent on “intellectual property.” In the First World, on the other hand, rent-seeking vultures have restricted the free flow of potentially life-saving technical information in many cases. (Many of the publications from First World sources on the topic of earth construction are behind paywalls. One refreshing exception in the United States is the Getty Institute.) This is one reason why the Third World may be better poised for post-Peak adaptation than the First World. Secondly, the universities and professionals of the Third World are every bit as capable and competent as those in the First World, and in fact they may be far more creative.

In the literature which I have discovered, there are two categories of discussion regarding performance of earthen structures: the performance of non-engineered structures and the performance, experimental testing and analysis of engineered earthen structures. These discussions reveal the following observations:

  1. Almost all of the literature states that typical non-engineered earthen structures perform very poorly when subjected to severe and sudden wind loads or seismic events. This applies both to rammed earth (also known as tapia, taipal or pise de terre), cob and adobe structures. Rammed earth constructions and other earth structures can be highly susceptible to damage from earthquakes and other ground motion.

  2. The mechanism of disintegration of earth walls for various types of earth construction have been studied via shake table and compression tests. Among other things, these tests have documented the anisotropy of multi-layer rammed earth walls. A material that is anisotropic has physical properties that vary at different locations and in different directions in the material rather than being uniform throughout the material. This is important if there is a concern that a wall made of anisotropic material might have material properties that are not constant throughout the wall.

  3. Techniques for stabilization and reinforcement of earth structures have been studied. One study focused on two particular approaches: internal reinforcement via chicken wire or bamboo, and external reinforcement with bamboo or wooden members. Internal reinforcement did not work nearly as well as external reinforcement, which spread earthquake stresses over a large wall area, dissipating earthquake energy without causing major cracking.

  4. Proper reinforcement of earthen walls is key to surviving earthquakes and other environmental events. Unreinforced earthen structures suffered a number of typical failure modes. In addition, walls or wall elements that are reinforced internally with biodegradable materials like straw have been known to fail due to degrading of the reinforcement by insects and rot.

  5. As a result of laboratory tests, mathematical modeling and observations of actual earth structures in the aftermath of actual earthquakes, a number of governmental agencies and NGO's have published earth construction design guides. Many of these design guides agree on key points. In addition, there are countries in the developing world and the Global South which have formulated or are formulating earth building codes. New Zealand is one such case. Their New Zealand Earth Building Standards can serve as a repository of best practices and a starting place for model codes for earth building in other countries. Unfortunately, access to the New Zealand standards is not free.

  6. In addition to design guides for building professionals and code-enforcing officials, certain governments and NGO's have developed earth construction manuals for non-professional, unskilled builders who would be typical in rural or poor urban populations. Among the governmental agencies disseminating this design information is SENA (Servicio Nacional de Aprendizaje,, a national public entity of Colombia in South America, which publishes literature for public education and vocational training throughout South America. In addition, the Indian Institute of Technology at Kanpur has published the IAEE Guidelines for Earthquake Resistant Non-Engineered Construction, which is available in PDF form free of charge at the IIT Kanpur National Information Centre of Earthquake Engineering website. A 2011 draft update of these guidelines is also available from the International Institute of Seismology and Earthquake Engineering in Japan. Such guidelines embody low-cost, effective approaches for building safe earthen structures.

  7. Researchers have studied the challenge of reinforcing and retrofitting existing earthen structures which have historical significance. Recommended retrofit practices are emerging. Many of these retrofit practices involve addition of bamboo reinforcement to the exterior surfaces of earth walls, both outside and inside an earthen structure, in order to spread forces and stresses so that they don't result in concentrated failure at one point.

Many more facts could be gleaned from the available literature, but unfortunately, I am out of time. However, a list of references and cited works is included at the end of this post. Enjoy!

Additional References And Resources:

  1. Seismic Behavior and Rehabilitation Alternatives for Adobe and Rammed Earth Buildings,” Luis. E. Yamin, Camilo A. Phillips, Juan C. Reyes, Daniel M. Ruiz, 13th World Conference on Earthquake Engineering, 2004.

  2. Modern and historic earth buildings: Observations of the 4th September 2010 Darfield Earthquake,” H.W. Morris, 9th Pacific Conference on Earthquake Engineering – Building and Earthquake-Resilient Society, April 2011.

  3. Non-Engineered Construction In Developing Countries – An Approach Toward Earthquake Risk Reduction,” Anand S. Arya, 12WCEE 2000, Ministry of Urban Development, Government of India.

  4. Review of Non-Engineered Houses in Latin America with Reference to Building Practices and Self-Construction Projects,” Aikaterini Papanikolaou, Fabio Taucer, European Commission Joint Research Centre, 2004.

  5. Seismic Performance of Mud Brick Structures,” Joseph Hardwick and Jonathan Little, University of Bristol, EWB-UK National Research Conference 2010 and Engineers Without Borders UK, 2010.

  6. Low-Cost and Low-Tech Reinforcement Systems for Improved Earthquake Resistance of Mud Brick Buildings,” Dominic M. Dowling and Bijan Samali, The Getty Institute.

  7. Assessing the Anisotropy of Rammed Earth,” Quoc-Bao Bui, Jean-Claude Morel, 11th International Conference on Non-Conventional Materials and Technologies, 2009.

  8. Planning and Engineering Guidelines for the Seismic Retrofitting of Historic Adobe Structures,” E. Leroy Tolles, Edna E. Kimbro, William S. Ginell, The Getty Institute, 2002.

  9. An Improved Means of Reinforcing Adobe Walls – External Vertical Reinforcement,” Dominic Dowling, Bijan Samali, Jianchun Li, SismoAdobe 2005, Lima, Peru.

  10. Earthquake Resistant Rammed-Earth (Taipal) Buildings,” J. Vargas, Catholic University of Peru.


Aimee said...

Thank you for this - my husband and I are preparing to build a small house in Oaxaca, Mexico - his hometown - and are leaning towards adobe as inexpensive, locally produced, durable, cool in summer (relatively speaking), and traditional. Luckily, this is a part of the world where, while adobe is no longer the most common building material, there are still plenty of people around expert in it's manufacture and construction.

However, one problem with adobe, if not very well sealed with plaster inside and out, is that many unattractive or dangerous bugs like to live in the walls. In central America, Chagas is of the most concern - a parasite carried by beetles that bite at night, after hiding in the walls during the day. Chagas can lead to heart failure, among many other unpleasant effects.

That makes me a little nervous, but not nervopus enough to avoid adobe, which has many advantages.

Aimee said...

What do you think the prospects are for average citizens in the United States over the next several years?

A few years ago, when I first began to get serious about preparing for a future of diminished resources, my sister asked me what I thought the U.S. would be like in ten or twenty years. "Do you think we are going to be like a third world country?" She asked. I said "Probably we are going to be more like Russia," I answered, meaning, a technically advanced society where all levels of services and expertise are theoretically available, but are in actual fact available to very few people as they become both more expensive and more geographically limited. I think collapse in the U.S. is likely to look a lot like the collapse of Soviet Russia. I think, along with Sharon Astik (Causabon's Book) that the simplest way to explain it is that we will simply be a poorer nation.

Especially if the forces that be succeed in re-directing a larger and larger share of our nation's wealth toward private hoarding and away from investment in infrastructure, health care, education, and the social safety net (and alas, I think they are succeeding) we can expect public utilities not just to get more expensive but to decline drastically in quality. In concrete terms, this means that when there is a power outage, it will take longer to get the power back on, because there aren't enough people employed by local governments. I expect water quality and delivery to decline drastically, although that will vary extremely by where one lives. Even in the water rich Pacific Northwest, the city of Seattle is raising rates 37% next year - and in one sense this is as it should be, because water is terribly undervalued, leading to waste and cavalierness everywhere. However, I can't help having the vision of Mexico in my head - water delivered for a couple of hours once or twice a week, the poor who depend on municipal water supplies with barely enough to drink and cook, and no way to bathe or wash clothes: the rich who can afford to buy water from private companies the only ones who are free from want. Road repair, garbage collection, sewer and waste water management will all be negatively impacted by the push to defund local and state governments.

The list of services provided by government on which Americans have come to depend (in addition to those mentioned above) is long - police, fire department, public schools, libraries, emergency medical care, veteran's benefits, subsidized child care, farm subsidies, and grants and low interest loans for higher education, research and development, social work, child protective services, public defenders, and indeed the entire criminal and civil justice system, unemployment benefits and job training…. I could go on, but why? The fact is that average Americans will have less and less access to all of these services in the near future. The concerted effort to starve all levels of government and to protect private wealth is only a delaying tactic on the part of the powerful - the unpleasant truth is that all of the above will happen anyway. The global financial crisis will not get better - ever. It will of course have a few more ups along with the downs, but the trend will be downhill from here on out. Our entire system is predicated on unending resource extraction and unending cost-free waste dumping into the communal global space - givens which are no longer viable. We have utterly failed to come up with a system to take the place of real resource consumption and goods manufacturing - the best we have done is the electronic cash shell game which has already busted several times and impoverished millions (while of course enriching a few; with no curbs on financial system power we can expect them to milk this game as long as possible).

Aimee said...


Real estate is in for a massive reshuffling, as people attempt to flee from the places that become unviable more quickly and relocate to places that have a decade or two more viability. Actually "real estate" is too polite a term for it - along with chaos in the domestic real estate market there will be chaos as large numbers of climate refugees move around the globe. Resource wars will break out, or intensify where they already exist. The border will become more and more highly militarized, and killings of refugees will become commonplace, perhaps formalized into some kind of war or perhaps carried out by vigilante citizens. But I have digressed from what all this means for the average American - it means jobs will be harder and harder to come by, and your money will buy less and less. It means most Americans are likely to be forced into debt to meet the most basic requirements of life. It means we will be taking care of our aging parents at home. It means we may have to take more responsibility for educating our children. We will be spending more money on food, and quite possibly eating a lot less of "luxury" foods like meat, seafood, and processed foods. For those of us who live ten or fifteen miles out of town, we may have to restrict our trips into to town to once a month or so - what if it costs $100 to buy the gas to make a run to the grocery store? What if when you get there you can't afford what you want to eat?

For every service that disappears, there will be a range of responses from ordinary citizens. Some of them are visible already - what happens in various settings as policing disappears? What does a community without the rule of law look like? In the inner city? In the far rural areas? In the inner city, maybe, you get gangs, and in rural areas, militias, as ordinary people try to fill the security gap left by civil authority. Of course there are also positive responses, and I have been heartened to see them springing up all over. I'm thinking of the Transition movement, of the growth of the informal economy (i.e. bartering), and the stunning resurgence of farmer's markets, gardening for food, and the renaissance in traditional arts like preserving and knitting. People I know barter all the time, everything from the use of a trailer to load hay to the services of a mechanic, electrician, or seamstress; from trading my apples for the use of your apple press on up to trading professional services. All this is good, but I wonder how long these informal systems will be able to continue to function as the overall quality of life declines. I hope that neighbors will pool resources to - say - buy water purification systems for the neighborhood after the city gives up on the local infrastructure, or get together to put up a large windmill for local power generation, but I have my doubts. When I look around, I see that the general tendency is to hoard and isolate.

Gotta go now - I have so much more to say but right now I need to clean and cook for the fourth of July!!

TH in SoC said...

Thanks for your answers to my questions. I saw your comment response on your blog, but I was just then rushing out of the house for a camping trip. We certainly do live in interesting times.